United States Office of Radiation and Indoor Air EPA 402-R-09-002 

 Environmental Protection Agency Radiation Protection Division (6608J) 2009

Potential 

Nano-Enabled 

Environmental 

Applications for 

Radionuclides
ii 

This page intentionally left blank. 
 Office of Radiation and Indoor Air 

 Radiation Protection Division 

January 2009 EPA/402/R-09/002

Potential Nano-Enabled 

Environmental 

Applications for 

Radionuclides 

By 

EnDyna, Inc. 

McLean, VA 22102 

EPA Contract No. 07-HQ-02407 

Project Officer 

Madeleine Nawar 

Radiation Protection Division 

U.S. Environmental Protection Agency 

Washington, DC 20460 
i 

Preface 

“Potential Nano-Enabled Environmental Applications for Radionuclides” is an 

informational document designed to familiarize interested parties with some of the 

emerging nanotechnologies, and to recognize their potential environmental applications 

and implications. Specifically, it is developed to assist in decision making for 

incorporating nano-enabled technologies in mitigation of environmental contaminants 

including radionuclides. The document represents a snapshot in time to elucidate some of 

the base knowledge of nano-science which has evolved over the last 5-10 years. For the 

purposes of this document, “nano-enabled technologies and/or processes” refer to 

technologies which are enabled by a nano subsystem. 

This document may be updated in the future, and if you have any comments on the 

document or suggestions for incorporation in future updates, please contact: Ms 

Madeleine Nawar, USEPA, ORIA, RPD, 1200 Pennsylvania Ave., NW (MC 6608J), 

Washington DC 20460-0001, USA, Phone: 202-343-9229, Fax: 202-343-2306, Email: 

nawar.madeleine@epa.gov 
ii 

Disclaimer 

The opinions expressed within this report do not necessarily represent the views of the 

U.S. Environmental Protection Agency (EPA). Mention of trade names or commercial 

products does not constitute endorsement or recommendation for use. Similarly, 

exclusions or absence of specific references is merely an indication that information 

related to that entity was not readily available during the development of this 

informational document. 
iii 

Acknowledgements 

This report was developed by the Radiation Protection Division (RPD) of the U.S. 

Environmental Protection Agency’s (EPA’s) Office of Radiation and Indoor Air (ORIA). 

Ms. Madeleine Nawar served as the EPA Project Manager. Several individuals provided 

valuable input on the content of this report throughout its development. Special 

acknowledgement and appreciation is extended to RPD management and colleagues for 

their support and encouragement. 

A multi-disciplinary set of individuals provided peer review are: 

• Jim Alwood, Chemical Control Division, Office of Pollution Prevention Toxic 

Substances. U.S. EPA 

• Terry Barton, Senior Environmental Scientist, Superfund and Technology 

Liaison Program, U.S. EPA Region 6 

• J. Michael Davis, Ph.D., Senior Science Advisor, National Center for 

Environmental Assessment, Office of Research and Development, U.S. EPA 

• Brendlyn Faison, Ph.D., Office of Science and Technology, U.S. EPA 

• Richard Mattick, [in collaboration with U.S. EPA regional superfund staff], 

Policy Analysis and Regulatory Management Staff, Office of Solid Waste and 

Emergency Response, U.S. EPA 

• Najm Shamim, Ph.D., Office of Pesticide Programs, Antimicrobials Division, 

U.S. EPA 

• Richard Wiggins, Ph.D., Senior Science Advisor; Research Planning and 

Coordination Staff/National Health and Environmental Effects Research 

Laboratory Office of Research and Development, U.S. EPA 

• Ronald Wilhelm, Senior Scientist, RPD, ORIA, U.S. EPA 

This document was prepared under Contract No. 07-HQ-02407, EnDyna, Inc., and under 

the sponsorship of ORIA. Madeleine Nawar of EPA's RPD served as the Project Officer. 

The primary authors were Dr. Smita Siddhanti and Dr. Ian Tasker, assisted by Daniel 

Ruedy, of EnDyna, Inc. The EnDyna project team wishes to acknowledge the 

contribution of the following individuals for their valuable comments, input, and 

suggestions for this document's improvement. 

• Rafaela Ferguson, RPD, ORIA, U.S. EPA 

• Dr. Eric Nuttall, the University of New Mexico 

• Dr. Igor Linkov, U.S. Army Corps of Engineers
iv 

Table of Contents 

Executive Summary ........................................................................................................... vii

 

1.0 Introduction................................................................................................................ 1

1.1 Definition of Nanotechnology.............................................................................. 1 

1.2 Purpose of This Report ......................................................................................... 1 

1.3 Background of Nanotechnology.......................................................................... 2 

1.4 Application of Nanotechnology ........................................................................... 3 

1.5 Risk Associated with Nanoparticles in the Environment ................................ 4 

1.5.1 Nanomaterial Properties Associated with Risk ....................................... 5 

1.5.2 Possible Approaches to Nanotechnology Risk Assessment .................. 6 

1.5.3 Data Gaps and Limitations for Nanomaterials Risk Assessment ......... 7 

1.5.4 Approaches to Managing Nanotechnology Risk ..................................... 9 

1.6 Nanotechnology for Environmental Remediation..........................................12 

1.6.1 Current Applications...................................................................................12 

1.6.2 Awareness of Potential Environmental Benefits....................................13 

1.6.3 EPA’s Involvement in Nanotechnology ....................................................14 

1.6.4 International Involvement in Nanotechnology .......................................18 

1.7 Nanotechnology for Environmental Remediation of Radionuclides ...........19 

1.7.1 Technical Status ..........................................................................................19 

1.7.2 Rational Approach to Design in Nanotechnology ..................................20 

1.8 Structure of This Report and Summary of Examined Technologies ...........21 

1.9 References ...........................................................................................................25 

 

2.0 Nano-Enabled Remediation Technologies .......................................................... 30

2.1 Introduction ..........................................................................................................30 

2.2 Zero-valent Iron Nanoparticles..........................................................................32 

2.2.1 Background..................................................................................................32 

2.2.2 Description...................................................................................................32 

2.2.3 Summary of Environmental Potential......................................................37 

2.2.4 References...................................................................................................37 

2.3 Self-Assembled Monolayers on Mesoporous Supports.................................39 

2.3.1 Description...................................................................................................39 

2.3.2 Operational Considerations.......................................................................43 

2.3.3 Summary of Environmental Potential......................................................43 

2.3.4 References...................................................................................................44 

2.4 Membranes: Nanofiltration and Affinity ..........................................................46 

2.4.1 Background..................................................................................................46 

2.4.2 Nanofiltration Membranes ........................................................................46 

2.4.3 Summary of Environmental Potential......................................................50 

2.4.4 Electrospun Fibers ......................................................................................50 

2.4.5 Surface Modified Membranes...................................................................52 

2.4.6 References...................................................................................................55 

2.5 Zeolites..................................................................................................................58 

2.5.1 Introduction..................................................................................................58 

2.5.2 Description...................................................................................................58 
v 

2.5.3 Potential Applications ................................................................................59 

2.5.4 Impacts, Hazards, Efficacy, and Limitations...........................................62 

2.5.5 Management of Zeolite Wastes................................................................62 

2.5.6 Summary of Environmental Potential......................................................64 

2.5.7 References...................................................................................................65 

2.6 Other Nanoparticles............................................................................................69 

2.6.1 Nanodiamonds ............................................................................................69 

2.6.2 Dendrimers ..................................................................................................72 

2.6.3 Argonne Supergel........................................................................................74 

2.6.4 Summary of Environmental Potential......................................................75 

2.6.5 References...................................................................................................75 

2.7 Uranium Reduction by Bacteria ........................................................................77 

2.7.1 References...................................................................................................83 

2.8 Carbon Nanotubes (Fullerenes) ........................................................................85 

2.8.1 Background..................................................................................................85 

2.8.2 Description...................................................................................................85 

2.8.3 Operational Considerations.......................................................................89 

2.8.4 Summary of Environmental Potential......................................................89 

2.8.5 References...................................................................................................90 

 

3.0 Nano-Enabled Sensor Technologies...................................................................... 94

3.1 Introduction ..........................................................................................................94 

3.1.1 Basics............................................................................................................94 

3.1.2 Chemical Sensors .......................................................................................95 

3.1.3 The Trend towards Miniaturization...........................................................96 

3.1.4 Opportunities ...............................................................................................97 

3.1.5 References...................................................................................................98 

3.2 “Lab-on-a-Chip” ....................................................................................................99 

3.2.1 Summary of Environmental Potential................................................... 102 

3.2.2 References................................................................................................ 102 

3.3 Microcantilever Sensors .................................................................................. 103 

3.3.1 Summary of Environmental Potential................................................... 107 

3.3.2 References................................................................................................ 107 

3.4 Spectroscopic Sensors .................................................................................... 109 

3.4.1 Probe Encapsulated by Biologically Localized Embedding ............... 111 

3.4.2 Surface Plasmon Resonance ................................................................. 112 

3.4.3 Summary of Environmental Potential................................................... 114 

3.4.4 References................................................................................................ 114 

3.5 Nanowire Sensors ............................................................................................ 117 

3.5.1 Background............................................................................................... 117 

3.5.2 Description................................................................................................ 117 

3.5.3 Summary of Environmental Potential................................................... 120 

3.5.4 References................................................................................................ 120 

3.6 Nanobelts and Nanorods................................................................................. 122 

3.6.1 Nanobelts .................................................................................................. 122 

3.6.2 Nanorods ................................................................................................... 123 

3.6.3 References................................................................................................ 126
vi 

 

4.0 Observations and Conclusions.............................................................................128

 

Appendix A: Acronyms....................................................................................................131

Appendix B: Glossary ......................................................................................................133

References for Figures....................................................................................................138
vii 

Executive Summary 

The remediation of radionuclides and heavy metals using current technology is generally 

a costly and challenging proposition. Though funds for new technology development are 

limited, the need for innovative technologies and transformational approaches continues 

to be strong. In recent years, nanotechnology has risen to the forefront and the new 

properties and enhanced reactivities offered by nanomaterials may offer a new, low-cost 

paradigm to solving complex environmental and engineering problems. Many U.S. 

federal agencies, including the U.S. Environmental Protection Agency (EPA), are 

strongly supporting a wide range of nanotechnology research. Similarly, other countries 

are also promoting research in this new field. 

Environmental technologies frequently emerge as an offshoot of other technological 

developments or scientific advances. They can also be further enabled by changes in 

regulatory approach or stakeholder acceptance. Technologies such as real-time 

contaminant measurements within the EPA Triad framework, bioremediation, permeable 

reactive barriers, in-situ chemical oxidation, and enhanced attenuation have all been 

added to the toolbox of environmental technologies over the past decade. During roughly 

the same period, nanotechnology has evolved from an interesting (albeit arcane) area of 

manufacturing science, to being heralded as a paradigm-shifting technological revolution 

in the mold comparable to that of information technology or biotechnology. Coupled with 

this broad evolution, there has been a considerable amount of interest in 

nanotechnologies for a wide variety of applications in environmental remediation and 

waste reduction. For example, zero-valent iron (ZVI) nanoparticles for the remediation of 

chlorinated organics have effectively become a commercially-available technology. A 

number of other technologies, such as nano-scale photocatalysts and improved 

nanofiltration membranes, are also nearing commercialization. 

Nanotechnologies applied to the remediation of radionuclides have been a slower area to 

develop; this may well have been predictable since experience shows that the pathway for 

development of radionuclide remediation technologies is generally burdened with 

difficulties. However, it is important to realize that—although our conceptual awareness 

of nanotechnology is relatively new—nanotechnologies have in fact been used safely and 

effectively in the management of radioactive waste almost from the start of the nuclear 

age; zeolites, now recognized as a nanotechnology due to their nanostructure, have been 

used as ion exchangers to remove radioactive components from aqueous waste solutions 

for half a century. 

In this report, the current, early stages of development of nanotechnology applications for 

remediation of radionuclides and heavy metals are divided into two areas: new 

remediation methods and advancements in sensors. Though developments in these fields 

still remain in their early stages, this report describes some of the more promising 

remediation nanotechnologies and new sensors, and attempts to extrapolate general 

developments in nanotechnologies to advances in radionuclide remediation and 

monitoring. Some emerging examples already exist in both radionuclide remediation and 

monitoring. For example, the “Lab-on-a-Chip” (LOC) device for analyzing solutions 
viii 

containing radionuclides and heavy metals is a promising development. Though a 

recently-emerged technology, the LOC device is being actively investigated in the United 

States and overseas for modification to radionuclide sensing, is advancing quickly, and is 

already being applied to radionuclides and heavy metals. Examples of other new sensor 

advances are reviewed and presented in this report. 

There is considerable potential for nanotechnology to assist with the remediation of 

radionuclide-contaminated sites. For example, ZVI nanoparticles, a reducing agent 

already implemented for the remediation of chlorinated organics in groundwater, are an 

excellent prospect for use as a reducing agent to precipitate uranium from contaminated 

groundwater. ZVI nanoparticles are commercially available, and field tests for 

remediation of heavy metals such as chromium (IV) have shown promise. Two 

advantages of ZVI are the greater aerial distribution in saturated porous media and a high 

degree of reactivity due to the greater surface area of these very fine particles. Another 

example is the Self Assembled Monolayers on Mesoporous Supports (SAMMS) 

technology, originally developed by the Department of Energy (DOE) primarily for 

mercury but also with radionuclides in mind, which has recently had its first field 

implementation. 

There are strong scientific basis and solid research demonstrating that nanotechnologies 

will make significant advances over a wide range of technological fields. Government 

agencies around the world and the commercial sector now invest billions of dollars into 

nanoscience and technology research and development. However, the amount of funding 

environmental nanoscience research and development receives represents only a fraction 

of this massive overall effort. Hence, environmental nanoscience has lagged significantly 

behind other application and development areas in the nanoscience field. Because of 

growing national and international interest in the environment, it is expected that 

environmental nanoscience will grow. 

This report presents a general introduction to nanotechnology, providing a broad context 

to its narrower focus on nanotechnology for environmental remediation and waste 

management. The introduction also addresses some risk considerations involving 

nanotechnology, and discusses nanotechnology as applied to both environmental 

remediation (in general) and the environmental remediation of radionuclides (in 

particular). The body of the document consists of two main sections, one surveying 

nanotechnologies for remediation, the other surveying nanotechnologies for sensors. 

These two sections are divided into chapters which describe a nanotechnology or group 

of related nanotechnologies, and include a brief summary of the environmental potential 

of each. 
1 

1.0 Introduction 

1.1 Definition of Nanotechnology 

Nanotechnology is the art and science of manipulating matter at the atomic or molecular 

scale and holds the promise of providing significant improvements in technologies for 

protecting the environment. While many definitions for nanotechnology exist, the U.S. 

Environmental Protection Agency (EPA) uses the definition developed by the National 

Nanotechnology Initiative (NNI), a U.S. Government research and development (R&D) 

program established to coordinate multi-agency efforts in nanoscale science, engineering, 

and technology. The NNI is comprised of 26 federal agencies, 13 of which have R&D 

budgets in nanotechnology. The NNI (NNI 2007) requires nanotechnology to involve all 

of the following: 

1. Research and technology development at the atomic, molecular, or 

macromolecular levels, in the length scale of approximately 1-100 nanometer 

(nm) range in any direction; 

2. Creating and using structures, devices, and systems that have novel properties and 

functions as a result of their small and/or intermediate size; and 

3. Ability to control or manipulate on the atomic scale. 

Nanotechnology is thus the technology of the extremely small; one nm is defined as one 

billionth of a meter. In comparison, 1 nm is one fifty-thousandth of the diameter of a 

human hair, or, if a nanometer was scaled to the diameter of a child’s marble, then a 

meter would have to be scaled to the diameter of the Earth. Nanotechnology is often 

regarded as being a product of the latter part of the twentieth century, a product of the 

drive towards miniaturization led by the semiconductor industry. However, in a broader 

sense, nanotechnology has been around, albeit unrealized as such, for a long time. Two 

thousand years ago the ancient Greeks used a permanent hair-dying recipe that worked by 

depositing 5 nm lead sulfide crystals inside hair. High-quality steel made in India before 

the turn of the first millennium has been shown to contain—and owe its outstanding 

properties to—carbide structures similar to modern carbon nanotubes. Medieval artists 

colored stained glass using metal nanoparticles. The difference between these ancient 

examples of “nanotechnology” and the current situation is the ability to understand—or at 

least embark on a path towards understanding—the fundamental principles underlying 

nanotechnological behavior, the ability to assess the current state of knowledge, and the 

ability to systematically plan for the future based on that knowledge. 

1.2 Purpose of This Report 

The purpose of this report is to assist EPA in its exploration of the potential for using 

nano-enabled technologies in the cleanup of radioactive contamination, and in decisions 

to assist with the development of viable technologies in this area. For the purposes of this 

report, “nano-enabled technologies” refers to technologies that are enabled by a nano 

sub-system. This report will be used to identify and evaluate emerging applications and 
2 

implications (both health and ecological) of nano-enabled technologies for the 

remediation of sites contaminated with radionuclides. 

1.3 Background of Nanotechnology 

The history of nanotechnology is generally understood to have begun in December 1959 

when physicist Richard Feynman gave a speech, “There's Plenty of Room at the Bottom” 

(Feynman 1959), at an American Physical Society meeting at the California Institute of 

Technology in which he identified the potential of nanotechnology. Feynman said it 

should be possible to build machines small enough to manufacture objects with atomic 

precision, and that if information could be written on an atomic scale, “all of the 

information that man has carefully accumulated in all the books in the world can be 

written ... in a cube of material one two-hundredths of an inch wide—about the size of 

the smallest piece of dust visible to the human eye.” He claimed that there were no 

physical laws preventing such achievements, while noting that physical properties would 

change in importance (e.g., gravity becoming less important), though surface phenomena 

would begin to dominate behavior. 

In 1974, Norio Taniguchi first used the word “nanotechnology” (Taniguchi 1974), in 

regard to an ion sputter machine, to refer to “production technology to get the extra-high 

accuracy and ultra-fine dimensions, i.e. the preciseness and fineness on the order of one 

nanometer.” In the 1980s, Eric Drexler authored the landmark book on nanotechnology, 

“Engines of Creation” (Drexler 1986), in which the concept of molecular manufacturing 

was introduced to the public at large. It is due to Drexler that much of the public’s 

imagination has been captured by the potential of nanotechnology and 

nanomanufacturing. In 1985, fullerenes, or “buckyballs,” were discovered (Kroto et al. 

1985). By the 1990s, nanotechnology was advancing rapidly. In 1990, the first academic 

nanotechnology journal was published, in 1993 the first Feynman Prize was awarded, and 

by 2000 President Bill Clinton announced the U.S. National Nanotechnology Initiative 

(NNI). NNI and other nanotechnology proponents now anticipate the development of 

nano-enabled tools to help address many current challenges facing the United States and 

the international community, including: 

• Clean, secure, affordable energy; 

• Stronger, lighter, more durable materials; 

• Low-cost filters to provide clean drinking water; 

• Medical devices and drugs to detect and treat diseases more effectively with fewer 

side effects; 

• Lighting that uses a fraction of the energy associated with conventional systems; 

• Sensors to detect and identify harmful chemical and biological agents; and 

• Techniques to clean up harmful chemicals in the environment. 

This document focuses on the last of these challenges—techniques to clean up harmful 

chemicals in the environmental. Nanotechnologies offer new and previously 

unanticipated possibilities due to new properties and behaviors that occur at the nano 

scale, which can be harnessed in a structured and planned manner. The growing ability to 
3 

design and tailor technologies to specific ends indicates that problems that were once 

regarded as impossible to solve can now be addressed in a rational manner. The size of 

nanoparticles allows nanoscale behavior to be introduced into areas inaccessible to 

conventional technologies. When material exists in the nanoparticulate form, it exhibits 

unusual behavior that has made it the subject of great interest. This unusual behavior is 

the result of two phenomena. First, the surface area-to-volume ratio of nanoparticles is 

much greater than that of larger particles. Nanoparticles in the 10 nm range can have 50% 

of their molecular structure exposed to the surface, a percentage that is millions of times 

greater than that of typical powdered materials. Since chemical reactivity and catalytic 

ability is directly related to surface area, chemical properties are greatly enhanced. 

Second, at the nanoparticle scale, quantum behavior that is typically masked in larger 

particles can be readily displayed. 

1.4 Application of Nanotechnology 

Descriptions of nanotechnology that characterize it purely in terms of the minute size of 

the physical features with which it is concerned—assemblies between the size of an atom 

and about 100 molecular diameters—make it sound as though nanotechnology is merely 

using infinitely smaller parts than conventional engineering. However, working matters 

are truly more complex; rearranging the atoms and molecules leads to new properties and 

unusual behaviors. A transition is apparent between the fixed behavior of individual 

atoms and molecules and the adjustable behavior of collectives. Many scientists are now 

investigating the fundamental nature of nanotechnology in a wide spectrum of academic 

fields—from the basic sciences to engineering. Much of known science (e.g., colloid 

science, electronics, chemistry, physics, and genetics) will be applicable, but augmented 

with exciting new breakthroughs. 

The potential applications of nanotechnology range across a broad scale. For example, in 

medical systems, it could be possible to improve the tissue compatibility of implants to 

create scaffolds for tissue regeneration, or perhaps even to build artificial organs. Further, 

new types of genetic therapies and anti-aging treatments could be possible. 

Nanotechnology is currently used by leading businesses and industrial research 

companies for a variety of technical and innovative applications. Examples include: 

• ExxonMobil is using zeolites, minerals with pore sizes of less than 1 nm, as a 

more efficient catalyst to break down or crack large hydrocarbon molecules to 

form gasoline. 

• IBM has added nanoscale layering to disk drives, thus exploiting the giant 

magnetoresistive effect to attain highly dense data storage. 

• Gilead Sciences is using nanotechnology in the form of lipid spheres, also known 

as liposomes, which measure about 100 nm in diameter, to encase an anticancer 

drug to treat the AIDS-related Kaposi’s sarcoma. 

• Carbon Nanotechnologies, a company co-founded by buckyball discoverer 

Richard E. Smalley, is making carbon nanotubes more affordable by using a new 

and more efficient manufacturing process. 
4 

• Nanophase Technologies is utilizing nanocrystalline particles, incorporated into 

other materials, to produce tough ceramics, transparent sun blocks, and catalysts 

for environmental uses, among other applications. 

Though vastly different in the outputs they produce, these companies all use 

nanotechnology to develop more efficient, affordable, and, most recently, 

environmentally-safe products. 

1.5 Risk Associated with Nanoparticles in the Environment 

 

As previously noted, the potential widespread application of nanomaterials in 

environmental remediation is made possible by the miniaturization of materials down to 

the nano-scale. However, this same enabling characteristic also influences risk by 

changing the particles' potential for mobility, exposure, absorption, reactivity, and 

toxicity. When a nanomaterial is used for environmental remediation, it is intentionally 

introduced into the environment to exploit its unique properties. For example, nano-sized 

colloidal iron nanoparticles can act as catalysts in redox reactions. Of particular concern 

is the potential mobility of nanoparticles out of targeted sites or tissues, or whether 

intentional or unintentional releases of highly mobile nano-particles into the environment 

could be controlled (CRS 2008). 

Nevertheless, nanomaterials can have side effects, and a risk assessment requires 

knowledge of their distribution in the environment and food chain. Risk assessment is 

required for understanding the nanoparticles’ behavior to evaluate potential risks 

associated with nanomaterial use for remediation. Side effects associated with the use of 

nanotechnology, especially environmental risks associated with residual nanomaterials’ 

fate and transport in the environment, are not yet fully explored and understood. 

Uncertainties of the nature and interaction of nanomaterials in the following areas add to 

the complexity of risk concerns. These include: uncertainty in relationship between size, 

surface area, and surface reactivity; and uncertainty in relationship of radionuclides and 

nanomaterials. A clear understanding of the relationship between these parameters is still 

evolving and is not yet clearly understood. Additionally, the relation between 

radionuclides and nanomaterials is not yet determined. 

Risk assessment is practiced by EPA and other federal agencies as a tool to evaluate risks 

associated with chemicals and radionuclides in the environment. Risk assessment 

approaches and procedures have been formulated by the National Academy of Sciences, 

and have been subsequently tailored to specific applications by EPA and other federal 

agencies. EPA risk assessment has four components: hazard identification, toxicity 

assessment, exposure assessment, and risk characterization. Although the risk assessment 

paradigm has been used successfully by the scientific community since the early 1980s, 

its application to nanotechnology requires incorporating an uncertainty in basic 

knowledge that is very large when compared to the uncertainty for other materials and 

pharmaceuticals. To do so requires an understanding of product life-cycle and the ability 

to communicate effectively with personnel, stakeholders, and regulators. 
5 

Although risk assessment/management of conventional chemicals is well established, 

nanotechnology risk assessment is an emerging field; there is a growing body of 

scientific literature dealing with potential associated risks, including: 

• Effects of nano-particle introduction on soil chemistry/fertility/texture; 

• Fate and transport (e.g., zero-valent iron (ZVI) or ZVI-uranium-contaminated 

nano-particles); 

• Exposure pathways and assessment (including environmental and occupational 

exposures, both chronic and acute); 

• Dose-response relationship and toxicity (including effects on organs such as 

lungs, gills, liver, kidneys, and immune systems); 

• Bioaccumulation and biomagnification (e.g., food chain); and 

• Effects on humans as well as effects on ecosystems, ranging from impacts at 

molecular (nano) scale through the microbial (microorganisms) and the meso 

(small animals) to the macro (large animal communities). 

The following sections provide a brief overview of: nanomaterial properties potentially 

associated with risk (1.5.1), possible approaches to nanotechnology risk assessment 

(1.5.2), data gaps and limitations for assessing nanomaterial risk (1.5.3), and an overview 

of the proposed frameworks for risk management (1.5.4). 

 

1.5.1 Nanomaterial Properties Associated with Risk 

 

Characteristics of nanomaterials potentially leading to increased toxicity, risks and 

associated modifying factors have been discussed in recent literature (Biswas and Wu 

2005, Borm and Muller-Schulte 2006, Borm et al. 2006, Gwinn and Vallyathan 2006, 

Kreyling et al. 2006, Medina et al. 2007, Nel et al. 2006, Oberdorster et al. 2007, Thomas 

and Sayre 2005). In general, the following properties of nanomaterials are discussed as 

potential risk drivers: 

• Chemical composition is one of the key factors discussed. Nanomaterials may be 

derived from bulk materials with known toxic properties. Moreover, in many 

cases a given nanomaterial can be produced by different processes yielding 

several derivatives of the same material. It is important to note that the chemical 

properties of particles at the nanometer size can differ significantly from the 

chemical properties of larger particles consisting of the same chemical 

composition. 

• Toxicity potential can be caused by either chemical toxicity based on chemical 

composition or stress or stimuli caused by the surface, size, and/or shape of the 

particle. Differentiation between these two toxic effects is not straightforward 

(Brunner et al. 2006), but the size of the particle may indirectly dominate the 

uptake of particles into cells (Limbach et al. 2005, Kreyling et al. 2006). 

• Surface reactivity can increase the harm caused by nanomaterial in a cell and 

reduce the potential for environmental degradation (Limbach et al. 2007). 

Materials with active surfaces are deemed more harmful than the materials that lack 

such surfaces. It should be noted that smaller particle size also means higher 

surface reactivity because more of the atoms are in the surface of the particle. 
6 

• Solubility and environmental mobility have been proven to greatly affect the risk 

associated with nanomaterials (Brunner et al. 2006). Higher mobility results in 

higher risk, and insoluble materials or materials with nanoparticles embedded in 

a bulk material matrix may be less bioavailable. 

• Agglomeration affects the toxicity as well. Particles that naturally agglomerate into 

larger units can be interpreted as less toxic. Three agglomeration classes (low, 

medium, and high) have been defined. In these, highest agglomeration 

corresponds to lowest risk. 

1.5.2 Possible Approaches to Nanotechnology Risk Assessment 

Though multiple frameworks for nanomaterials risk assessment and risk management 

have been proposed, none has been formally adopted as regulatory tool (Linkov et al. 

2008). Two examples of the representative risk assessment frameworks are presented in 

this section, while multiple risk assessment and risk management frameworks are 

summarized in Section 1.5.5. 

NanoRisk Framework 

 

The NanoRisk Framework (www.NanoRiskFramework.com) was developed by DuPont 

Corporation and the Environmental Defense Fund to address the environmental, health, 

and safety risks of nanomaterials across all stages of product life cycle. It recommends 

six distinct steps: 

• Step 1. Describe Material and Application. Develop a general description of the 

nanomaterial and its intended uses, based on information in the possession of the 

developer or in the literature. The user also identifies analogous materials and 

applications that may help fill data gaps in this and other steps. 

• Step 2. Profile Lifecycle(s). The second step defines a process to develop three 

sets of profiles—of the nanomaterial's properties, its inherent hazards, and its 

associated exposures throughout the material's lifecycle. The properties profile 

identifies and characterizes a nanomaterial's physical and chemical properties. 

The hazard profile identifies and characterizes the nanomaterial's potential safety, 

health, and environmental hazards. 

• Step 3. Evaluate Risks. In this step, all the information generated in the profiles is 

reviewed in order to identify and characterize the nature, magnitude, and 

probability of risks presented by this particular nanomaterial and its anticipated 

application. In so doing, the user considers gaps in the lifecycle profiles, 

prioritizes those gaps, and determines how to address them—either by generating 

data or by using, in place of such data,” reasonable worst case” assumptions or 

values. 

• Step 4. Assess Risk Management. Here the user evaluates the available options 

for managing the risks identified in Step 3 and recommends a course of action. 

Options include engineering controls, protective equipment, risk communication, 

and product or process modifications. 
7 

• Step 5. Decide, Document, and Act. In this step, appropriate to the product's 

stage of development, the user consults with the appropriate review team and 

decides whether or in what capacity to continue development and production. 

Consistent with a transparent decision-making process, the user documents those 

decisions and their rationale and shares appropriate information with the relevant 

stakeholders, both internal and external. 

• Step 6. Review and Adapt. Through regularly scheduled reviews as well as 

triggered reviews, the user updates and re-executes the risk evaluation, ensures 

that risk-management systems are working as expected, and adapts those systems 

in the face of new information (e.g., regarding hazard data) or new conditions 

(such as new or altered exposure patterns). 

Through these six steps, the framework seeks to guide a process for risk evaluation and 

management that is practical, comprehensive, transparent, and flexible. 

Comprehensive Environmental Assessment Approach (Davis 2007):

The Comprehensive Environmental Assessment (CEA) approach combines life-cycle 

perspective with the risk assessment paradigm. This systematic approach could guide 

research strategy for assessing the risks of nanotechnology and avoid unintended 

consequences (Davis 2007). The CEA approach begins with assessing product life cycle 

stages including material production or extraction, manufacturing processes, distribution,

storage, use, and disposal (including recycling). At any given stage of the life cycle, 

nanoscale substances and/or associated materials (e.g., manufacturing by-products) might 

enter one or more of the environmental media—air, water, soil—and affect humans and 

ecological receptors through multiple pathways, including food web. It is important to 

identify nanomaterials in their primary form and, further, to consider the transport and 

transformation processes they may undergo during the product life cycle. 

To evaluate exposure in a comprehensive manner, it is important to consider, among 

other things, both aggregate exposure across routes (inhalation, ingestion, and dermal 

absorption) and cumulative exposure to multiple (primary and secondary) pollutants. The 

CEA approach tends to focus on the range of exposure scenarios, including microenvironmental and high-end exposures, not just “typical” or “average” exposure levels.

The human health and ecological hazards associated with respective contaminants can be 

described qualitatively and, if possible, quantitatively. 

 

1.5.3 Data Gaps and Limitations for Nanomaterials Risk Assessment 

Though the use of nanomaterials is increasing, understanding the environmental fate and 

transport, toxicity, and potential human health and ecological risks associated with 

nanomaterial use remains extremely limited. This is due to a variety of barriers, including 

proprietary nature of information; and lack of standardization in nomenclature, metrics, 

and materials (CRS 2008). 
8 

Risk assessment requires information related to the following four components: hazard 

identification, toxicity assessment, exposure assessment, and risk characterization. For 

human health and environmental risk assessment of nanomaterials, the current knowledge 

base contains data gaps. The literature has established these knowns (things we know that 

we know) and unknowns (things we know that we don’t know) in the nanotechnology 

context for the four components (Davis 2007). Some of the data gaps for each of the risk 

assessment components are described below. 

• Predicting the environmental fate of nanomaterials: At present there are few 

available studies on the environmental fate of nanomaterials but they are not 

adequate to predict the fate of nanomaterials based on their fundamental 

properties. Nanomaterials released to soil and ground water as part of remedial 

activities can be strongly sorbed into soil due to their high surface areas, and 

therefore become immobile. On the other hand, nanomaterials are small enough to 

fit into the smaller spaces between soil particles, and therefore might travel farther 

than larger particles before becoming trapped in the soil matrix. In addition to the 

nanomaterial properties discussed above, types and properties of the soil and 

water can affect nanomaterial mobility. Since nanoparticles are likely to be 

transported as colloids, the mobility of mineral colloids in soils and sediments and 

the availability of humic substances are important considerations. Additionally, in 

the presence of various soils having different pH, and radionuclides, 

nanomaterials may form different byproducts. The fate of nanomaterials in 

aqueous environments is controlled by solubility or dispersability; interactions 

between the nanomaterial and natural and anthropogenic chemicals in the system; 

and biological and abiotic processes. Light-induced photoreactions are often 

important in determining the environmental fate of chemical substances. 

• Nanomaterial toxicity and bioaccumulation potential: Past literature provides some 

evidence of toxicity and bioaccumulation potential, but the results are generally 

inconclusive. Laboratory testing of nanomaterial uptake has shown a wide range of 

potential affects on tested organisms, including bioaccumulation potential, 

mortality, and biomarker-response. Nevertheless, the concentration of nanoparticles 

used in this and other studies may far exceed concentrations that could potentially 

result from those that would be associated with site remediation. 

• Exposure estimation: When a nanomaterial is used for an environmental 

application, exposure estimation might not be straightforward. Multiple variables 

could influence nanomaterial exposure assessment, including the characterization 

of the effectiveness of variations in biological reactivity, size, shape, and charge, 

as well as factors that complicate the straightforward estimation of exposure such 

as metabolism, excretion, and adduction to biological molecules. For example, 

several studies on carbon nanotubes have shown that the toxicity and distribution 

of nanoparticles is dependent upon the presence of functional groups, impurities, 

fiber length, and aggregation status. 
9 

• Risk Characterization: Given estimates of exposure and toxicity, the final step 

involved in estimating the hazard of contaminant exposure is risk characterization 

(i.e., the likelihood of adverse environmental impact at varying degrees of 

exposure). Risk characterization must be developed separately for each 

nanomaterial, or even for the same nanomaterials with different functions or at 

different environmental life-cycle stages. Given the required effort, detailed risk 

characterization may not be possible. Decision tools and databases could be 

developed to allow the use of all available information, as well as proxy data for 

making the best judgment on risk characterization. 

1.5.4 Approaches to Managing Nanotechnology Risk 

As a field of science, nanotechnology is still young and uncertainty in basic knowledge 

does not lend itself to fully informed and accurate risk assessments, but scientific 

evidence does exist that suggest some nanoparticles may be hazardous. Some regulatory 

and industry representatives caution that inadequate government oversight, or even a 

perceived lack of oversight, could lead to consumer rejection of an entire range of 

products incorporating nanotechnology. Such a reaction would significantly hinder 

development and industry growth. To prevent a loss of consumer confidence, academic 

researchers, policy analysts, and some nanotechnology entrepreneurs have been working 

with federal agencies that are responsible for protecting the environment, workers, and 

consumers (CRS 2008). 

Assessment and management of the potential risks associated with nanotechnology is a 

challenge with which U.S. agencies and countries in the European Union (EU) are 

beginning to come to terms. Despite all the limitations, some progress in approaching 

risk-based nanotechnology regulation is being made. In the EU for example, the 

European Commission (EC) has adopted the opinion of the Scientific Committee on 

Emerging and Newly Identified Health Risks (SCENIHR) on definitions for 

nanotechnology. This advance takes one of the first steps towards risk assessment and 

regulation: standardizing nomenclature, metrics, and materials. In addition, the EU is 

currently conducting research to compare nanotechnology regulatory policies in the EU 

with those in the United States. Similar to previous efforts to reach coordination on 

regulation (including beef, chemicals, and genetically modified organism regulations), 

those involved are hopeful that this research will improve transatlantic regulatory 

cooperation of nanotechnology in the future (NanoReg News 2008). 

A review of current nanomaterial risk management frameworks and related documents is 

summarized in Table 1. Details of these can be found in the references provided. 
10 

Table 1: Current nanomaterial risk frameworks 1 

Agency Focus Citation 

U.S. Environmental 

Protection Agency 

(EPA) White Paper 

Comprehensive framework intended to 

set forth current scientific knowledge 

and its gaps related to possible 

environmental benefits of 

nanotechnology, as well as potential 

risks from environmental exposure to 

nanomaterials. 

(US EPA 2007) 

Federal Drug 

Administration 

(FDA) 

Report intended to help assess questions 

regarding the adequacy and application 

of the FDA’s regulatory authority to 

nanomaterials, and to provide findings 

and recommendations to the FDA 

Commissioner. 

(US FDA 2007) 

Woodrow Wilson 

Center 

Paper intended to describe the 

possibilities for government action to 

deal with the adverse effects of 

nanotechnology, and to provide 

evidence relevant for determining what 

needs to be done to manage 

nanotechnology. 

(Davies 2006) 

Environmental 

Defense (EDF)-

DuPont 

Comprehensive framework for the 

responsible development, production, 

use, and end-of-life disposal of 

nanomaterials, intended for use by 

companies and other organizations. 

(EDF-DuPont 2007)

Québec Commission Comprehensive discussion of the 

scientific, legal, and ethical implications 

of nanotechnology, intended to help 

uphold the protection of health and the 

environment, as well as respect for 

many values such as dignity, liberty, 

integrity, justice, transparency, and 

democracy. 

(QC 2006) 

Royal Society Comprehensive framework intended to 

summarize current scientific knowledge 

and applications of nanotechnology, and 

(RS & RAE 2004) 

 

1 Linkov, I., Satterstrom, K., (2008). “Nanomaterial Risk Assessment and Risk 

Management: Review of Regulatory Frameworks.” In: Linkov, I., Ferguson, E., 

Magar, V. (in press). “Real Time and Deliberative Decision Making: Application to 

Risk Assessment for Non-chemical Stressors. Springer, Amsterdam. 
11 

Agency Focus Citation 

to identify possible health and safety, 

environmental, ethical, and societal 

implications or uncertainties. 

Department for 

Environment, Food, 

and Rural Affairs 

(DEFRA) 

Trial Voluntary Reporting Scheme to 

collect data from organizations in the 

nanotechnology industry to help the 

United Kingdom develop appropriate 

controls for risks to the environment and 

human health from nanomaterials. 

(UK DEFRA 2006) 

Responsible 

NanoCode 

Paper intended to highlight key issues 

that emerged from a business workshop 

on nanotechnology, including 

development of a responsible 

nanotechnology code. 

(RNC 2006) 

European 

Commission 

Scientific 

Commission on 

Emerging and Newly 

Identified Health 

Risks (SCENIHR) 

Technical document intended to assess 

the appropriateness of current risk 

assessment methodologies for the risk 

assessment of nanomaterials, and to 

provide suggestions for improvements 

to the methodologies. 

(EC SCENIHR 

2007) 

European 

Commission Action 

Plan 

Plan intended to help Europe build on 

its strengths and advances to ensure that 

nanotechnology research is carried out 

with maximum impact and 

responsibility, and that the resulting 

knowledge is applied in products that 

are useful, safe, and profitable. 

(EC 2005) 

International Risk 

Governance Council 

(IRGC) Policy Brief 

Brief intended to assist policy makers in 

developing the processes and 

regulations to enable the development 

and public acceptance of 

nanotechnology. 

(IRGC 2007) 

IRGC White Paper 1 Comprehensive framework intended to 

advance the development of an 

integrated, holistic, and structured 

approach for the investigation of risk 

issues and the governance processes and 

structures pertaining to them. 

(IRGC 2005) 

IRGC White Paper 2 Comprehensive framework which 

applies general IRGC risk governance 

framework to the field of 

nanotechnology. 

(IRGC 2006) 
12 

In response to public concern for the protection of the environment and human health 

from the potential hazards of nanomaterials, EPA has released a nanotechnology research 

strategy to protect the environment (EPA 2008). In addition, EPA has also recently 

completed the Basic Program phase of the EPA's Nanoscale Materials Stewardship 

Program (NMSP), where some organizations are showing their support for a successful 

beginning of a voluntary information collection program (NanoReg News 2008). 

Currently, the main challenge facing EPA is minimizing nanotechnology's potential for 

unintended, harmful consequences, while pursuing the positive aspects of nanomaterial 

use, including potential of environmental remediation applications. In the Office of 

Research and Development's (ORD) recently released Draft Nanomaterial Strategy (EPA 

2008), EPA both builds on and is consistent with the NNI's previous reports, as well as its 

own Nanotechnology White Paper (EPA 2007). In Draft Nanomaterial Strategy, EPA 

gives special attention to its mission to protect the environment and its specific needs for 

being able to regulate nanotechnology (NanoReg News 2008). It also identifies four 

major areas for future research: 

• environmental fate and transport, 

• human health implications, 

• risk assessment methodology, and 

• risk mitigation strategies. 

Initially, EPA's research will focus on nanoscale titanium dioxide, ZVI, nanosilver, 

carbon nanotubes, and cerium oxide, with the intention that the resulting body of 

knowledge can be extrapolated for classes of nanomaterials in the future, particularly as 

nomenclature, metrics, and materials become standardized. Anticipated outcomes from 

this research program are expected to be focused research products that address risk 

assessment and risk management needs for nanomaterials in support of the various 

environmental statutes for which EPA is responsible (NanoReg News 2008). 

 

1.6 Nanotechnology for Environmental Remediation 

1.6.1 Current Applications 

Recent advances in the design, production, and fundamental understanding of 

nanomaterials have led to preliminary investigations of their use in the remediation of 

chlorinated organics in the subsurface, and to a wide range of suggestions for their 

potential use in the remediation of other environmental contaminants, including those at 

radiologically-contaminated sites. The potential for innovative use is directly related to 

the enhanced chemical activity resulting from the increased surface area and the 

manifestation of quantum effects, yet it also takes advantage of a third feature of 

nanoparticles, namely their ability to be transported to areas inaccessible to other 

remediation approaches. For example, if we consider bioremediation, part of the promise 

lies in the fact that microbes capable of destroying organic contaminants can directly 

access subsurface pore structure that is too small for regular particles to access. However, 

there is still much of the pore structure in the subsurface that is too small even for 
13 

microbes. Nanoparticles are typically two orders of magnitude smaller than bacteria and 

can thus be transported to an occluded contaminant that is hidden from direct bacterial 

contact. Current applications, discussed in more detail in Sections 2 and 3 of this 

document, include zeolites and nanoparticulate ZVI. 

1.6.2 Awareness of Potential Environmental Benefits 

Since nanotechnology and nanomaterials are comparatively new technologies, only 

partial knowledge of the environmental fate, transport, effects, and risks associated with 

them is available, and some of this information appears to be contradictory. Ultimately, 

this knowledge will be crucial in deciding whether a technology involving nanomaterials 

is an appropriate remedy. Concerns in this regard have been so strong that a report by the 

Royal Society (RS) and the Royal Academy of Engineering (RAE) in the United 

Kingdom has recommended “that the use of free (that is, not fixed in a matrix) 

manufactured nanoparticles in environmental applications, such as remediation, should 

be prohibited until appropriate research has been undertaken and it can be demonstrated 

that the potential benefits outweigh the potential risks (RS/RAE 2004).” Thus, it is 

important to conduct a comprehensive review and evaluation of both the effectiveness 

and the potential impacts of available treatment options. 

Within all of the discussion about nanotechnology opportunities, consideration of the 

application of nanotechnology to environmental problems seems to have been 

subordinated to consideration of risks of nanotechnology. Though the potential has been 

recognized, often it is the risks posed to human health and the environment that have 

dominated discussion of nanotechnology and the environment. The term “disruptive 

technology” was introduced in 2003 (Uldrich and Newberry 2003) to describe a new 

technology that is significantly cheaper (or performs better) than a current technology, 

and will revolutionize worldwide markets by superseding the existing technology. The 

industries on which nanotechnology will likely have a disruptive effect were analyzed 

and at the high-end (i.e., largest impact) included: 

• Healthcare 

• Long-term care 

• Electronics 

• Telecom 

• Packaging 

• United States Chemical 

• Plastics 

• Apparel 

• Pharmaceutical 

• Semiconductor 

At the low-end, the industries included: 

• Cosmetics 

• Chocolate 

• Batteries 

• Blue jeans 
14 

• Khakis 

• Fluorescent tagging 

• Mouthwash 

At the time of Uldrich and Newberry 2003, the environmental industry was not classified 

on the list. 

1.6.3 EPA’s Involvement in Nanotechnology

Fortunately, nanotechnology in the environmental industry is progressing, gradually 

becoming more advanced and better recognized. EPA is obligated to protect human 

health and safeguard the environment by better understanding and addressing potential 

risks from exposure to nanoscale materials, but it is also interested in researching and 

developing the possible benefits of nanotechnology. Since 2001, EPA has played a 

leading role in funding research and setting research directions for developing 

environmental applications of nanotechnology. Two recent examples demonstrate EPA’s 

commitment: the “Nanotechnology White Paper” and the “Workshop for 

Nanotechnology on Site Remediation.” 

In February 2007, EPA published the “Nanotechnology White Paper” (EPA 2007) based 

on the work of a cross-Agency workgroup created in December 2004 by EPA’s Science 

Policy Council. It describes key science issues EPA should consider to ensure that society 

accrues the important environmental protection benefits that nanotechnology may offer. 

The document notes that since 2001, EPA’s Science To Achieve Results (STAR) grant 

program has funded 36 research grants—totaling nearly $12 million—in the application 

of nanotechnology to protect the environment, including the development of: 1) low-cost, 

rapid, and simplified methods of removing toxic contaminants from water; 2) new 

sensors that are more sensitive for measuring pollutants; 3) green manufacturing 

nanomaterials; and 4) more efficient, selective catalysts. Additional projects have been 

funded through the Small Business Innovation Research (SBIR) program, and there are 

14 recent STAR program projects focused on studying the possible harmful effects, or 

implications, of engineered nanomaterials. 

This white paper also describes the benefits, risk assessment, and responsible 

development of nanotechnology, and outlines the involvement in nanotechnology by 

various EPA Offices including: 

• Office of Pollution Prevention and Toxics (OPPT) — activities include reviewing 

premanufacture notifications for a number of nanoscale materials that have been 

received under the Toxics Substances Control Act, initiating a Nanoscale 

Materials Stewardship Program to encourage submission and development of 

information for nanoscale materials (see 

http://www.epa.gov/oppt/nano/stewardship.htm), public outreach, and 

international engagement on nanotechnology issues with the Organization of 

Economic Cooperation and Development and International Organization for 

Standardization (ISO).
15 

• Office of Air and Radiation/Office of Transportation and Air Quality 

(OAR/OTAQ) — activities include reviewing an application for registration of a 

diesel additive containing cerium oxide. Cerium oxide nanoparticles are being 

marketed in Europe as on- and off-road diesel fuel additives to decrease 

emissions, and some manufacturers claim fuel economy benefits. 

• Office of Pesticide Programs (OPP) — activities include working with members 

of the pesticide industry regarding licensing/registration requirements for 

pesticide products that utilize nanotechnology. 

• Office of Solid Waste and Emergency Response (OSWER) — activities include 

investigating potential implications and applications of nanotechnology by such 

means as: an October 2005 workshop on “Nanotechnology for Site Remediation” 

organized with EPA’s ORD and several other federal agencies; and a July 2006 

symposium entitled, “Nanotechnology and OSWER: New Opportunities and 

Challenges.”

• Office of Enforcement and Compliance Assurance (OECA) — activities include 

reviewing Agency information on nanotechnology (e.g., studies, research); 

evaluating existing statutory and regulatory frameworks to determine the 

enforcement issues associated with nanotechnology; evaluating the science issues 

for regulation/enforcement that are associated with nanotechnology, and; 

considering what information OECA’s National Enforcement Investigations 

Center (NEIC) may need to consider to support the Agency.

Importantly, EPA’s white paper presents a set of key nanotechnology recommendations, 

including: 

• Environmental Applications Research. The Agency should continue to 

undertake, collaborate on, and support research to better understand and apply 

information regarding environmental applications of nanomaterials. 

• Risk Assessment Research. To ensure that research best supports Agency 

decision-making, EPA should conduct case studies to further identify unique risk 

assessment considerations for nanomaterials. The Agency should also continue to 

undertake, collaborate on, and support research to better understand and apply 

information regarding nanomaterials’: 

o chemical and physical identification and characterization, 

o environmental fate, 

o environmental detection and analysis, 

o potential releases and human exposures, 

o human health effects assessment, and 

o ecological effects assessment. 

• Pollution Prevention, Stewardship, and Sustainability. The Agency should 

engage resources and expertise to encourage, support, and develop approaches 

that promote pollution prevention, sustainable resource use, and good product 

stewardship in the production, use, and end-of-life management of nanomaterials. 

Additionally, the Agency should draw on new, “next generation” 

nanotechnologies to identify ways to support environmentally beneficial 
16 

approaches such as green energy, green design, green chemistry, and green 

manufacturing. 

• Collaboration and Leadership. The Agency should continue and expand its 

collaborations regarding nanomaterial applications and potential human health 

and environmental implications. 

• Intra-Agency Workgroup. The Agency should continue to convene a standing 

intra-Agency group to foster information sharing on nanotechnology science and 

policy issues. 

• Training. The Agency should continue and expand its nanotechnology training 

activities for scientists and managers. 

Another recent example of EPA’s involvement in using nanotechnology for better 

environmental remediation is the October 2005 “Workshop on Nanotechnology for Site 

Remediation” (EPA 2005). This workshop explored the place of nanotechnology among 

existing remedial techniques, considered the overall state of the science, and examined 

some case studies (primarily of nanoparticulate ZVI). Workshop participants also 

discussed research needs and data gaps. Their findings may be summarized into four 

broad categories (i.e., performance; toxicity; basic nanoscience; and fate and transport) as 

follows: 

Performance

• Better understanding of injection techniques and control of nanoparticle 

movement in the subsurface; better ways to overcome other limitations on 

material emplacement such as permeability changes over time with injections; 

• Development of a set of performance-assisting tools such as validation methods, 

modeling, scale-up equations, statistics, and QA/QC approaches; 

• Development of performance metrics/standards of the nanoparticles, including 

manufacturing, size, shape, storage, and property and reactivity standards for 

nanoparticles; 

• Development of performance assessment and performance prediction tools for the 

contaminants being remediated; 

• Development of in-situ sensors, real-time techniques, and analytical methods for 

detecting nanoparticles; 

• Better understanding of the effects of treatment trains (options and optimization 

of combinations) and synergies of multiple contaminants “cocktail treatment”; 

• Need national test sites covering major geologic settings to permit rigorous field 

demonstration; and 

• Need for contingency ability to remove nanoparticles from wastewater and 

drinking water. 

Toxicity 

• Recognizing gaps in data and in the understanding of toxicological effects on 

humans, flora, and fauna and how low risk toxicity can be measured in the 

environment; 

• Recognizing lack of information on fate, stability, and potential for transformation 

(for example heavy metal sequestration); 
17 

• Understanding the difference between maximizing remedial effects while 

minimizing toxicological problems; 

• Integrating toxicological behavior into risk-based decision making; and 

• Better understanding of macro-scale toxicity properties and whether it can be 

extrapolated to nano-scale using knowledge of size, shape, chemistry. 

Basic Nanoscience

• Discovering the existence of intrinsic nano-scale processes and mechanisms (such 

as surface area versus electronic effects and bulk properties versus surface effect); 

• Discovering the difference between extrapolating macro-scale and micro-scale to 

nano-scale, or determining if there is there a unique nano-scale physico-chemistry 

that cannot be identified at the macro-scale; 

• Better understanding needed of agglomeration behavior to control both in-situ 

reactivity and transport; and 

• Recognizing the need for better information products and information synthesis. 

Fate and Transport • Major risks and uncertainties seen in fractured media and in the transport of 

sequestered contaminants; 

• Better monitoring and detection techniques are needed for fate and transport as 

well as for performance studies; and 

• Need much better information on site-to-site variability of fate and transport 

rather than assuming that behavior identified at one site can be applied widely; 

Investigation of fate and transport of nanoparticles for environmental applications is 

important since an understanding in this area is critical to evaluating performance (the 

need to know how far and in what form the nanoparticle will travel to perform its 

function), toxicity (the risk of the nanoparticle traveling unanticipated distances in very 

toxic forms), and cost (directly related to performance). Though the fate of the 

nanoparticle will depend heavily on the characteristics and material of the nanoparticle, 

recent work has indicated that transport may not be as grave a concern as once thought. It 

has been noted that the common assumption that nanoparticles will be highly mobile in 

porous media due to their tiny size in comparison with pore spaces, is an 

oversimplification (Tratynek 2006). The mobility of nanoparticles in the saturated 

subsurface is the product of the number of nanoparticle collisions with the porous 

medium per unit transport distance (where collisions arise from Brownian diffusion, 

interception and gravitational sedimentation) and the sticking coefficient. Calculations for 

a typical subsurface using a range of sticking coefficients indicates that transport will 

range from millimeters to a few tens of meters. These calculations seem to have been 

borne out in field tests with iron nanoparticles used to remediate chlorinated organics. 

In fact, an area of current interest is how to coat particles so that they will not stick and 

will travel further to attain their remedial purpose. This indication of limited travel only 

applies in porous media and would not be expected to hold in fractured geologic media or 

in surface water. As a result, EPA is continuing investigations of fate and transport 
18 

through research2 such as that on the environmental fate of single-walled carbon 

nanotubes in the estuarine environment at the University of South Carolina. Similar work 

on environmental fate and transport is also being conducted at a number of academic 

centers, such as the Center for Biological and Environmental Nanotechnology (CBEN) at 

Rice University, which aims to understand and manipulate the wet/dry interface between 

nanosystems and biological systems, and the Nanomaterials in the Environment, 

Agriculture, and Technology Organized Research Unit (NEAT-ORU) at the University of 

California Davis, which emphasizes research on the interaction of materials and the 

natural and man-made environment. 

1.6.4 International Involvement in Nanotechnology

The United States is not alone in exploring the benefits of nanotechnology for 

environmental remediation and its implications on human health, welfare, and the 

environment. Two recent reports from Europe help paint a picture of current thinking. 

A 2007 report from the United Kingdom’s Department for Environment, Food and Rural 

Affairs (DEFRA) titled “Environmentally Beneficial Nanotechnologies: Barriers and 

Opportunities” (Walsh 2007), was commissioned to provide an overview of the areas 

where nanotechnology could have a beneficial environmental impact above current 

technology and the barriers preventing its adoption. Five nanotechnological applications 

were subject to detailed investigation: fuel additives, solar cells, the hydrogen economy, 

batteries, and insulation. 

A workshop on “Nanotechnologies for Environmental Remediation” (Rickerby and 

Morrison 2007) was convened at the Joint Research Center in Ispra, Italy in 2007. This 

workshop brought leading scientists together from across the EU to present their latest 

work in environmental remediation and discuss issues including: 

• The most effective nanotechnologies for pollution prevention or cleanup; 

• The dependability and proximity to market of remediation techniques based on 

nanotechnologies; 

• The additional research needed to exploit the full potential of nanotechnology for 

remediation; 

• The most promising environmental nanotechnologies and those that should be 

further explored; 

• The potential risks of using nanotechnologies in remediation applications. 

• Whether there is a need for targeted funding for infrastructure to support 

nanotechnologies for environmental remediation; and 

• The opportunities for setting up EU collaborative projects on environmental 

nanotechnologies. 

The issues of environmental remediation were considered to be quite substantial and 

poorly addressed by conventional technologies. They include access to clean drinking 

 

2

 ORD STAR 
19 

water; removal of airborne pollutants; and the cleanup of industrially-contaminated sites 

(in particular ex-military sites). Although there have been a number of laboratory 

demonstrations of nanotechnology applications for environmental cleanup, there remains 

the issue of translating these into industrial-level processes. The workshop consisted of 

two principal sessions: “Water Treatment and Purification,” and “Air, Water and Soil 

Decontamination.” Participants discussed the following important issues: 

• Photocatalytic treatment of water for degradation of pollutants and the destruction 

of microorganisms; 

• Titanium dioxide (TiO2) nanopowder immobilization on substrates to produce a 

photogalvanic system with a photoanode for photodegradation of organic 

pollutants; 

• Photocatalytic inactivation of bacterial spores and photocatalytic disinfection of 

water; 

• Membrane nanofiltration for the treatment of process and wastewater; 

• Colloidal and interface chemistry; 

• Development of a system utilizing iron-precipitating bacteria to co-precipitate; 

• Organic and inorganic pollutants, such as arsenic; 

• Sol-gel synthesis of nanosized TiO2 particles on polypropylene fibers for the 

photocatalytic degradation of organic pollutants; 

• Ultra nanocrystalline diamond used as an electrode for water treatment and 

disinfection; 

• Feasibility of a Lab-on-a-Chip (LOC) device for analyzing highly radioactive 

solutions; 

• Development of catalytic trap technology and advanced systems for particulate 

matter; 

• Incorporating TiO2 in building materials or surface coatings to impart selfcleaning and de-polluting properties; and 

• A double skin sheet reactor (DSSR) for water purification. 

 

1.7 Nanotechnology for Environmental Remediation of Radionuclides 

 

1.7.1 Technical Status 

 

Discussion in Section 1.6 has illustrated that research of radionuclide remediation is 

lacking in the growing interest of environmental nanotechnology. The mention in Section 

1.6.4 of investigating the feasibility of an LOC device for analyzing highly radioactive 

solutions is an encouraging exception. In spite of this current situation, the potential for 

nanotechnology to assist with the remediation of radionuclide-contaminated sites is 

considerable. For example, zeolites, nanostructured materials that can also be made as 

nanoparticles, already have a long history of use in the treatment of liquid radioactive 

waste. ZVI nanoparticles, a reducing agent already implemented for the remediation of 

chlorinated organics in groundwater, are an excellent prospect for use as a reducing agent 

to precipitate uranium form contaminated groundwater. LOC is a recently emerged 

sensing technology that is being actively investigated for modification to radionuclide 

sensing. The Self-Absorbed Monolayers on Mesoporous Supports (SAMMS) technology, 
20 

originally developed by DOE primarily for mercury, but also with radionuclides in mind, 

has recently had its first field implementation. 

In addition to these examples of current or near-term applications of nanotechnology to 

radionuclides, it is clear from the analysis of the scientific and engineering principles that 

other technologies can be developed, and it is clear from analysis of broader 

governmental and industrial issues and initiatives that a rational approach to design of 

nanomaterials and nanotechnologies is being pursued. Two examples, one technical 

(rational design of organic ligands) and the other programmatic (Chemical Industry R&D 

Roadmap for Nanomaterials by Design) demonstrate the potential of a rational design 

approach. 

1.7.2 Rational Approach to Design in Nanotechnology 

The rational design of complexants or sequestrants in organic chemistry draws on 

expertise from a number of areas of chemistry, including supramolecular chemistry, 

molecular recognition, host-guest chemistry, molecular mechanics, and molecular 

modeling. The conceptual origins go back over 100 years to the idea developed by Emil 

Fischer, who proposed that enzyme-substrate interactions occur through a “lock and key” 

mechanism. Subsequent research was stimulated by work such as the elucidation of DNA 

structure, where non-bonding interactions were critical to understanding the threedimensional structure. As far back as the mid to late 1990s, government and industry 

began shifting their focus in the area of separations from complexants and sequestrants to 

separations platforms such as membranes. The U.S. chemical industry presents one of the 

best examples of this structured approach. The U.S. chemical industry is the world's 

largest, accounting for over 26% of global chemical production (over $450 billion per 

year) (DOE 2007). The chemical industry worldwide is the largest component of the 

nanotechnology industry; worldwide the nanotechnology industry is estimated at $130 

billion (Cientifica 2007), of which the chemical industry accounts for approximately $69 

billion (53%). With its enormous scientific and engineering basis (accounting for one out 

of every four U.S. patents) and knowledge of varied product requirements, the chemical 

industry is well positioned and motivated to explore a rational approach to 

nanotechnology. 

Currently, much nanomaterial development occurs through empirical or Edisonian R&D, 

in which a nanomaterial structure with interesting properties is discovered, an application 

is subsequently sought and development of a product retaining the nanoproperty is 

attempted. This approach is hit or miss. As a result, a smaller-than-optimal number of 

products are produced even though time-to-market can be rapid. Against this background, 

in 2003, the Chemical Industry Vision2020 Technology Partnership (Vision2020) issued 

its technology roadmap, “Chemical Industry R&D Roadmap for Nanomaterials by 

Design: From Fundamentals to Function (Chemical Industry Vision2020 2003).” 

Vision2020 is an industry-led partnership process among public and private sector 

stakeholders in the chemical and allied industries. The chemical industry has recognized 

both the significance of nanomaterials to its operations and markets and a solution-
21 

oriented approach to materials development, or “nanomaterials by design”, is needed. 

Conceptually, nanomaterials by design is the ability to employ scientific principles in 

deliberately creating structures with nanoscale features (e.g., size, architecture) that 

deliver unique capabilities for target applications and require detailed understanding of 

science at the nanoscale. The general concept of rational design originated within the 

chemical community after it found early applications in pharmaceutical design. 

Vision2020’s roadmap presented four major research areas for nanotechnology 

development: 

• Manufacturing and Processing—developing unit operations and robust scale-up 

and scale-down methodologies for manufacturing, with emphasis on synthesis, 

separation, purification, stabilization, and assembly. 

• Characterization Tools—developing analytical tools for measuring and 

characterizing nanomaterials both in scientific research and in numerous areas of 

production.

• Fundamental Understanding and Synthesis—developing new paradigms for the 

creation and controlled assembly of nanoscale building blocks, based on an 

understanding of physics and chemistry at the nanoscale. 

• Modeling and Simulation—developing computational tools to predict bulk 

properties of materials that contain nanomaterials and can bridge between scales 

from atoms, to self-assembly, to devices. 

Once these developments are achieved, large numbers of diverse products could rapidly 

enter global markets to solve long-standing problems and stimulate economic growth for 

decades to come. A library of nanomaterials and synthesis techniques could be 

established by 2020 for use by material producers and end-users worldwide, offering 

diverse, high-quality nanomaterial building blocks with well-characterized compositions, 

stable architectures, and predicted properties. Safe, reproducible, cost-effective, and 

clearly-defined manufacturing and assembly methods would be available to incorporate 

nanomaterials into systems and devices designed to perform specified functions, while 

retaining nanoscale attributes. The roadmap suggests a twenty-year period for the 

completion of this development. 

1.8 Structure of This Report and Summary of Examined Technologies 

The remainder of this report is organized into three sections listed below: 

• Section 2: Nano-Enabled Remediation Technologies (each technology description 

is followed by references specific to that technology) 

• Section 3: Nano-Enabled Sensor Technologies (each technology description is 

followed by references specific to that technology) 

• Section 4: Observations and Conclusions 
22 

Table 2 below provides a summary of the technologies examined in this document and 

includes a reference to the section in which the technology is discussed, a brief summary 

of the technology, an estimate of the maturity level for the technology and the main 

medium in which the technology operates. 

Table 2: Summary of Examined Nanotechnologies and Nanosensors 

Technology Section Summary Maturity Media 

Zero-valent 

Iron (ZVI) 

Nanoparticles 

Section 

2.2 

Page 32 

ZVI nanoparticles are a 

nanotechnology modification 

of the established ZVI 

technology in which the ZVI 

undergoes oxidation and 

consequently is able to reduce 

species, such as chlorinated 

organics and higher valency 

toxic metals (e.g., uranium and 

chromium). 

The use of macro-scale ZVI 

in subsurface permeable 

reactive barriers is a wellestablished technology. 

Nano-scale ZVI has already 

undergone field 

demonstrations. 

Aqueous 

Self-Absorbed 

Monolayers on 

Mesoporous 

Supports 

(SAMMS) 

Section 

2.3 

Page 39 

SAMMS is a separations 

technology designed for the 

removal of soluble species in 

aqueous solution. It is likely to 

be a strong competitor to 

conventional ion exchangers, 

solid-supported complexants, 

or other solid sorbents. The 

fundamental scientific 

underpinnings make SAMMS 

an extremely flexible 

separations technology. 

Commercially available and 

being used in the field for 

mercury remediation, with 

ongoing development for a 

wide range of toxic and 

radioactive metals. 

Aqueous 

Nanofiltration 

Membranes 

Section 

2.4 

Page 

46 

Nanofiltration and reverse 

osmosis membranes are a 

mature separation technology 

designed for the removal of 

particulate and soluble species 

in aqueous solution. They 

occupy the part of the 

spectrum of filtration 

technologies where extremely 

small particulates and soluble 

species can be removed from 

aqueous solution. 

Conventional nanofiltration 

and reverse osmosis 

membranes are wellestablished. The use of 

insights from recent 

nanotechnology 

developments for improved 

membranes is well 

underway and commercial 

products are expected to be 

available in the near future. 

Aqueous 

Zeolites Section 

2.5 

Page 58 

Zeolites are a well-established 

ion exchange technology that 

is used, among a wide range of 

other, non-separatory 

industrial applications, for the 

treatment aqueous waste 

streams containing radioactive 

solutes. Zeolites are a 

nanotechnology that had 

A mature, long-established 

technology, widely used for 

the treatment of radioactive 

waste streams and under 

ongoing development. 

Aqueous/

soils 
23 

Technology Section Summary Maturity Media 

established uses predating the 

general concept of 

nanotechnology. 

Other 

Nanoparticles 

Section 

2.6 

Page 

69 

Nanodiamonds, dendrimers, 

and the Argonne Supergel are 

presented to demonstrate the 

range of possibilities offered 

by nanoparticles— particularly 

the ease with which a 

nanoparticle can be 

incorporated into another 

technology application and the 

ability to engineer specific 

properties into a nanoparticle 

at the atomic level. 

Various depending on 

specific technology. 

Various 

depending on 

specific 

technology. 

Uranium 

Reduction by 

Bacteria 

Section 

2.7 

Page 77 

By using the appropriate 

micro-organism and nutrient 

addition, soluble uranium (VI) 

can be converted in-situ to 

much less soluble uranium 

(IV) by enzymatic reduction. 

The technology concept is 

mature and commercially 

available. 

Aqueous, 

soil, subsurface 

Carbon 

nanotubes 

(fullerenes) 

Section 

2.8 

Page 

85 

A class of hollow, spherical, or 

ellipsoidal molecules 

composed entirely of carbon 

atoms in a cage-like structure. 

They have a range of potential 

applications, from sensing 

elements, to components of 

advanced nano-composite 

materials that may enable 

better membranes for reverse 

osmosis and nanofiltration. 

Nanotubes are now 

commercially available in 

“tons-per-year” quantities. 

Applications are in the 

laboratory stage with future 

development likely to speed 

up now that availability has 

been increased and cost 

decreased. 

Aqueous 

Lab-on-a-Chip 

(LOC) 

Section 

3.2 

Page 99 

LOC is a platform that can 

integrate a number of 

laboratory analytical functions, 

such as separations and 

analysis of components of a 

mixture, on a single 

microprocessor chip using 

fluid volumes in the nanoliter 

and lower range, thus allowing 

realization of small, portable 

equipment. 

The technology is 

commercially available for 

biological research. 

Aqueous 

Microcantilever 

Sensors 

Section 

3.3 

Page 103 

A microcantilever is an 

extremely small beam 

supported at one end and 

capable of well-defined 

bending and vibrational 

The technology concept is 

mature and commercially 

available. 

Aqueous 
24 

Technology Section Summary Maturity Media 

behavior that can be accurately 

monitored. When the 

microcantilever surface is 

modified so as to be able to 

bind a target species, the 

changes in vibrational 

behavior allow concentration 

of the target species to be 

determined. 

Spectroscopic 

Sensors 

Section 

3.4 

Page 109 

Spectroscopic measurements, 

particularly fluorescence 

spectroscopy, are one of the 

most sensitive conventional 

detection technologies, 

routinely going to the single 

molecule level in the 

laboratory. Nano-enabled 

technologies promise to 

expand the availability and 

application of these 

techniques. Probe 

Encapsulated by Biologically 

Localized Embedding 

(PEBBLE), surface plasmon 

resonance, nanobelts and 

nanorods are discussed as 

examples. 

Various, depending on 

specific technology. 

Primarily 

aqueous 

Nanowire 

Sensors 

Section 

3.5 

Page 

117 

Nanowires are solid, rod-like 

materials with diameters in the 

5-100 nm range and are most 

often made from metals or 

semi-conducting metal oxides. 

Their main application is 

expected to be in sensors, with 

the underlying phenomenon 

that is exploited being the field 

effect upon which field effect 

transistors are based. 

Early stage of development. Aqueous 

Nanobelts and 

Nanorods 

Section 

3.6 

Page 

122 

Nanobelts are a class of 

nanostructure often viewed as 

a type of nanowire. Nanobelts 

form ribbon-like structures 

with widths of 30-300 nm, 

thicknesses of 10-30 nm, and 

lengths in the millimeter 

range. Nanorods are solid 

nanostructures 

morphologically similar to 

nanowires but with aspect 

ratios of approximately 3-to-5. 

Under investigation for 

various applications. 

Various 

depending on 

specific 

technology. 
25 

This report does not address technologies complementary to radionuclide remediation or 

sensing. For example, if a subsurface plume were to contain both Resource Conservation 

and Recovery Act (RCRA) organics and radionuclides as contaminants, the material was 

brought to the surface, and a problematic mixed waste was produced; a nanotechnology 

that could destroy the RCRA organic would accomplish much in assisting with the 

management of the radionuclide. Though this type of consideration is beyond the scope 

of this report, it represents yet another approach by which nanoparticles can assist in the 

management of radionuclide problems. 

In addition to the technologies that are presented in this report, there are a number of 

other technologies or scientific concepts that over the short term, as nanotechnology 

advances, may have remedial potential for radionuclides. The prediction of future 

technology success is a task always fraught with risks, particularly as the time period of 

the prediction grows. It is often pointed out that at the end of the nineteenth century many 

scientists believed that all of the basic fundamental principles governing physics and 

chemistry were known, and that few big discoveries left with only details remaining. The 

difficulties in technical prediction still remain. Some of the choices for the following 

sections are obvious. For instance, technologies such as ZVI nanoparticles, SAMMS, and 

zeolites have already found commercial or near-commercial applications in the treatment 

of radionuclides. Others are included since they are being actively researched for closely 

similar applications. For instance, dendrimers are being examined for application in the 

treatment of heavy metals and the transfer of understanding from heavy metals to 

radioactive metals is usually fairly straightforward; it is very common in research to use 

the lanthanides as models for the actinides since the non-radioactive lanthanides are much 

easier to work with than the radioactive actinides and useful predictions and 

extrapolations of behavior from one class to the other can be made. For the rest of the 

technologies common factors employed in the analysis of technology potential were used. 

For example, factors such as the existence of a standardized framework or platform 

within which to work, the existence of a wealth of related knowledge and supporting 

research, the technology offering a technically elegant or conceptually compelling 

solution to a problem, or the robustness and flexibility of a technology are all positive 

indicators of its likely success. The reader should of course understand that, particularly 

in a rapidly developing field, there is always inherent uncertainty in making 

extrapolations of likely technology success. 

 

1.9 References 

Biswas, P. and C.-Y Wu. 2005. Nanoparticles and the environment. Journal of the Air 

& Waste Management Association: 55, 708-746. 

Borm, P., and D. M  ̈uller-Schulte. 2006. Nanoparticles in drug delivery and environmental exposure: same size, same risks? Nanomedicine: 1(2), 235-249. 

Borm, P., D. Robbins, S. Haubold, T. Kuhlbusch, H. Fissan, K. Donaldson, R. Schins, V. 

Stone, W. Kreyling, J. Lademann, J. Krutmann, D. Warheit, E. Oberdorster. 2006. The 
26 

potential risks of nanomaterials: a review carried out for ECETOC. Particle and Fibre 

Toxicology: 3(11). 

Brunner, T., P. Wick, P. Manser, P. Spohn, R. Grass, L. Limbach, A. Bruinink, W. Stark. 

2006. In vitro cytotoxicity of oxide nanoparticles: Comparison to asbestos, silica, and the 

effect of particle solubility. Environmental Science & Technology: 40(14): 4374-4381. 

Chemical Industry Vision2020 Technology Partnership. 2003. Chemical Industry R&D 

Roadmap for Nanomaterials by Design: From Fundamentals to Function.

Cientifica. 2007. Halfway to the trillion Dollar market? A Critical Review of the 

Diffusion of Nanotechnologies. London, April 2007. 

Congressional Research Service (CRS). 2008. Engineered Nanoscale Materials and 

Derivative Products: Regulatory Challenges. CRS Report for Congress. January 22, 2008. 

Order Code RL34332. 

Davis, J.M., 2007. How to Assess the Risks of Nanotechnology: Learning from Past 

Experience. Journal of Nanoscience and Nanotechnology. Vol. 7, 402-409, 2007. 

Davies, J. Clarence, 2006. Managing the Effects of Nanotechnology. Woodrow Wilson 

International Center for Scholars Project on Emerging Nanotechnologies. Washington 

DC 20004-3027. 

http://www.nanotechproject.org/process/files/2708/30_pen2_mngeffects.pdf. 

Department of Energy (DOE). 2007. Industrial Technologies Program: Chemicals 

Industry of the Future. Website. Accessed December 2007. 

http://www1.eere.energy.gov/industry/chemicals/. 

Drexler, K.E. 1986. Engines of Creation · The Coming Era of Nanotechnology. Anchor 

Books, New York. 

Environmental Protection Agency (EPA). 2005-B. U.S. EPA Workshop on 

Nanotechnology for Site Remediation U.S. Department of Commerce, Washington, DC. 

October 20-21, 2005. 

es.epa.gov/ncer/publications/workshop/pdf/10_20_05_nanosummary.pdf 

EPA 2007. U.S. EPA Nanotechnology White Paper; EPA 100/B-07/001. EPA Science 

Policy Council, Washington, DC.

es.epa.gov/ncer/nano/publications/whitepaper12022005.pdf 

EPA. 2008. Draft Nanotechnology Research Strategy; EPA/600/S-08/002. United States 

Environmental Protection Agency, Office of Research and Development, Washington 

DC. 
27 

European Commission (EC). 2005. Communication from the Commission to the Council, 

the European Parliament and the Economic and Social Committee: Nanosciences and 

nanotechnologies: An action plan for Europe 2005-2009. B-1050, Brussels, Belgium. 

http://ec.europa.eu/research/industrial_technologies/pdf/nano_action_plan_en.pdf. 

EC Scientific Committee on Emerging and Newly-Identified Health Risks (EC 

SCENIHR), 2007. Opinion on the appropriateness of the risk assessment methodology in 

accordance with the technical guidance documents for new and existing substances for 

assessing the risks of nanomaterials. B-1049 Brussels, Belgium. 

http://ec.europa.eu/health/ph_risk/committees/04_scenihr/docs/scenihr_o_010.pdf. 

Environmental Defense-DuPont Nano Partnership (ED-DuPont). 2007. Nano Risk 

Framework. http://www.environmentaldefense.org/documents/ 

6496_Nano%20Risk%20Framework.pdf. 

Feynman, R. 1959. There's Plenty of Room at the Bottom. Speech given at American 

Physical Society Meeting, California Institute of Technology, December. Accessed at 

http://nanoparticles.org/pdf/Feynman.pdf. 

Gwinn, M. and V. Vallyathan. 2006. Nanoparticles: Health effects—pros and cons. 

Environmental Health Perspectives: 114(2): 1818-1825. 

International Risk Governance Council (IRGC). 2005. White Paper on Risk Governance: 

Towards an Integrative Approach. By Ortwin Renn with Annexes by Peter Graham. CH1219 Geneva, Switzerland. http://www.irgc.org/IMG/pdf/ 

IRGC_WP_No_1_Risk_Governance__reprinted_version_.pdf. 

International Risk Governance Council (IRGC). 2006. White Paper on Nanotechnology 

Risk Governance. By Ortwin Renn and Mike Roco with Annexes by Mike Roco and 

Emily Litten. CH-1219 Geneva, Switzerland. 

http://www.irgc.org/IMG/pdf/IRGC_white_paper_2_PDF_final_version-2.pdf. 

International Risk Governance Council (IRGC). 2007. Policy Brief: Nanotechnology 

Risk Governance: Recommendations for a global, coordinated approach to the 

governance of potential risks. CH-1219 Geneva, Switzerland. 

http://www.irgc.org/IMG/pdf/PB_nanoFINAL2_2_.pdf. 

Kreyling, W., M. Semmler-Behnke, W. M  ̈oller. 2006. Health implications of nanoparticles. 

Journal of Nanomaterial Research: 8: 543-562. 

Kroto, H.W., J.R. Heath, S.C. O'Brien, R.F. Curl and R.E. Smalley. 1985. C60: 

Buckminsterfullerene. Nature. 318(6042): 162-163. 

Limbach, L., Y. Li, R. Grass, T. Brunner, M. Hintermann, M. Muller, D. Gunther, W. 

Stark. 2005. Oxide nanoparticle uptake in human lung fibroblasts: Effects of particle size, 
28 

agglomeration, and diffusion at low concentrations. Environmental Science & Technology:

39(23): 9370-9376. 

Limbach, L., P. Wick, P. Manser, R. Grass, A. Bruinink, W. Stark. 2007. Exposure of 

engineered nanoparticles to human lung epithelial cells: Influence of chemical 

composition and catalytic activity on oxidative stress. Environmental Science & 

Technology: 41(11): 4158-4163. 

Linkov, I., E. Ferguson, V. Magar. In press. Real Time and Deliberative Decision 

Making: Application to Risk Assessment for Non-chemical Stressors. Springer, 

Amsterdam. 

Linkov, I., K. Satterstrom, J. Steevens, E. Ferguson, R. Pleus. 2007. Multi-criteria 

decision analysis and environmental risk assessment for nanomaterials. Journal of 

Nanoparticle Research. 9: 543-554. 

Medina, C., M. Santos-Martinez, A. Radomski, O. Corrigan, M. Radomski. 2007. 

Nanoparticles: pharmacological and toxicological significance. British Journal of 

Pharmacology: 150: 552-558. 

NanoReg News. 2008. NanoReg Report: Policy News for the Nanotechnology Value 

Chain. February 15, 2008. Volume 5, Issue 3. Accessed March, 2008. 

http://www.nanoregnews.com/. 

National Nanotechnology Initiative (NNI). 2007. Website. Accessed December 2007. 

http://www.nano.gov/. 

Nel, A., T. Xia, L. M ̈adler, N. Li. 2006. Toxic potential of materials at the nanolevel. 

Science. 311: 622-627. 

Oberd  ̈orster, G., V. Stone, K.. Donaldson. 2007. Toxicology of nanoparticles: A historical 

perspective. Nanotoxicology. 1(1): 2-25. 

Québec Comisión de l’éthique de la science et de la technologie (QC), 2006. Position 

Statement: Ethics and Nanotechnology: A Basis for Action. Québec G1V 4Z2. 

http://www.ethique.gouv.qc.ca/IMG/pdf/Avis-anglaisfinal-2.pdf. 

Responsible NanoCode (RNC). 2006. Workshop report: How can business respond to the 

technical, social and commercial uncertainties of nanotechnology? 

http://www.responsiblenanocode.org/documents/Workshop-Report_07112006.pdf 

Rickerby, D. and M. Morrison. 2007. Report from the Workshop on Nanotechnologies 

for Environmental Remediation, JRC Ispra 16-17 April 2007. Institute for Environmental 

Sustainability. 
29 

Royal Society and Royal Academy of Engineering (RS & RAE), 2004. Nanoscience and 

nanotechnologies: opportunities and uncertainties. Science Policy Section, The Royal 

Society, London. http://www.nanotec.org.uk/finalReport.htm. 

Taniguchi, N. 1974. On the Basic Concept of ’Nano-Technology.’ Proceedings of the 

International Conference on Production Engineering, Tokyo, Part II, Japan Society of 

Precision Engineering. 

Thomas, K. and P. Sayre. 2005. Research strategies for safety evaluation of nanomaterials, 

part i: Evaluating the human health implications of exposure to nanoscale materials. 

Toxicological Sciences. 87(2): 316-321. 

Tratynek, P.G. and R.L. Johnson. 2006. Nanotechnologies for Environmental Cleanup. 

Nanotoday. 1(2). May 2006. 

Uldrich, J. and D. Newberry. 2003. Next Big Thing Is Really Small: How 

Nanotechnology Will Change the Future of Your Business. Crown Publishing Group, 

New York. 

UK Department for Environment Food and Rural Affairs (UK DEFRA). 2006. UK 

Voluntary Reporting Scheme for Engineered Nanoscale Materials. London SW1P 3JR. 

Available at: http://www.defra.gov.uk/environment/nanotech/policy/pdf/vrsnanoscale.pdf

U.S. Food and Drug Administration (US FDA). 2007. Nanotechnology: a report of the 

U.S. Food and Drug Administration Nanotechnology Task Force. July 25, 2007. 

Available via DIALOG http://www.fda.gov/nanotechnology/taskforce/report2007.html

Walsh, B. 2007. Environmentally Beneficial Nanotechnologies: Barriers and 

Opportunities. Report prepared for the United Kingdom Department for Environment, 

Food and Rural Affairs. Oakdene Hollins, Aylesbury, The United Kingdom. 

 
30 

2.0 Nano-Enabled Remediation Technologies 

2.1 Introduction 

In dealing with the remediation of environmental contamination or the closely-related 

concern of managing wastes, options for treating non-radiological (though potentially 

very hazardous) materials can be divided into two broad categories: separation of the 

contaminant and transformation of the contaminant. For example, if an aqueous stream is 

contaminated with trichloroethylene (TCE), the stream could be cleaned by passage 

through a bed of activated charcoal to separate the TCE from the stream, or by passage 

over a bed of ZVI, in which case the ZVI would transform the TCE. In the case of 

radionuclide contamination, the situation is complicated by the fact that no amount of 

transformation will ever remove the radiological characteristic of the waste—a uranium 

atom will always remain a uranium atom no matter how it speciates chemically. 

Transformations may be useful, but only to the extent that they assist in bringing about a 

separation. For radiological contamination, the separations of interest may be the removal 

of the radioactive species from its host matrix (i.e., an extraction), or it may involve 

processes such as fixation or stabilization, in which the radioactive material is separated 

from any mobilization and/or transport pathways so that the risk it poses is reduced or 

eliminated altogether by preventing it from being made available to a receptor. 

The remediation of radionuclide-contaminated sites has been problematic for decades. 

Radionuclides typically remain a matter of concern even at concentrations that are orders 

of magnitude lower than those for most non-radiological materials. Further, the 

geological matrix can present considerable heterogeneities even over small distances and 

is inherently difficult to characterize. The situation is further complicated by the timeline 

for developing remedial technologies. In contrast to enabling technologies such as 

sensors, remedial technologies are generally much more time-consuming and involve 

considerably higher costs and risks. These problems are amplified when radionuclides are 

involved. Though the novel chemical and physical properties offered by nanoparticles 

may yield new approaches to remediation, the fundamental difficulties posed by 

radionuclides will not disappear. This does not mean that nanoparticles offer little 

promise for environmental remediation. On the contrary, the potential appears to be great, 

but it is more likely to come in the areas of remediation of non-radiological contaminants, 

pollution prevention through the development of greener manufacturing processes, better 

waste treatment of non-radiological contaminants, and sensors than in the area of 

remediation of radiological material. 

Having provided this cautionary background, the research involved in preparing this 

report indicates that nanotechnology is likely to provide some useful tools for the toolbox 

of remediation technologies applicable to radionuclide-contaminated sites. For the past 

two decades, it has been recognized that environmental contamination by radionuclides 

constitutes one the most difficult environmental problems. The cost of remediation of 

such sites may be enormous. Major decreases in anticipated costs do not seem to be likely 

through incremental improvements to existing approaches and transformational 

alternatives that have been actively sought. Since nanotechnology is still in its infancy, 
31 

the possibility of transformational approaches arising should not be dismissed, even if 

there is little indication at present regarding how this will come about. 

Already, nanotechnology does offer some intriguing possibilities. One example is that 

macroscale ZVI has been used successfully for years as a means of treating chlorinated 

organics in groundwater via use of permeable reactive barriers (PRBs). Nanoscale ZVI is 

currently being investigated for the same application, exploiting the fact that its 

rheological properties allow it to be injected. ZVI has also been investigated as a 

reductant to transform materials of concern, such as chromium and uranium, from their 

higher valency, more soluble forms, to lower valency, and soluble forms possessing 

lower risk. It seems likely that nanoscale ZVI may offer the same chemical reductant 

properties, possibly even enhanced, with the flexibility of injectability. This conclusion 

involves an extrapolation, but it is a fairly small one. A second example, and one that 

does not involve an extrapolation, is zeolites—nanostructured, ion-exchanging 

separations materials that have been used in radioactive material waste management for 

half a century. A third example is the Self-Assembled Monolayers on Mesoporous 

Supports (SAMMS) technology, which offers a new platform for separations agents. This 

technology is currently being demonstrated for mercury removal and, in combination 

with the fundamental understanding already available, the extrapolation to a technology 

for the separation of radionuclides is small. 

Separations may be the area where nanotechnology makes its biggest impact in 

remediation. Carbon nanotubes can be incorporated into membranes and permit 

extremely fast fluid flow; they are under active investigation as a desalination 

technology. The combination of existing knowledge on ligand design—an area of 

fundamental importance to separations science—with new nanostructures, such as 

dendrimers, may offer greatly improved separations performance. The following sections 

describe technologies or technology concepts that have either been demonstrated for 

radionuclide treatment, such as zeolites, or that can be comfortably extrapolated to 

radionuclides, such as ZVI. Since a certain degree of extrapolation is necessarily 

involved, the survey in this report is not intended to be comprehensive, but rather seeks to 

provide information on reasonable possibilities that may yield technologies in the near 

future. The technologies examined in this report are: 

• ZVI nanoparticles 

• SAMMS 

• Membranes: nanofiltration and affinity 

• Zeolites 

• Other nanoparticles 

• Uranium reduction by bacteria 

• Carbon nanotubes 
32 

2.2 Zero-valent Iron Nanoparticles 

2.2.1 Background 

The massive surface area and unique properties of nanoparticles have led to much 

research on their application to environmental remediation. Across the broad array of 

environmental concerns, research ranges from the use of TiO2 nanoparticles for 

photocatalytic treatment of nitrous oxides in plant emissions, to the use of naturally 

occurring metal oxide nanoparticles for the treatment of organic contaminants in 

groundwater. There are, however, few examples of commercial-scale technologies that 

use nanoparticles for environmental remediation of non-radiological materials, and even 

fewer for remediation of radionuclides. The closest example to a commercial technology 

is the use of iron nanoparticles as a reductant for the remediation of chlorinated organics 

in water; this is a direct modification of the use of iron filings or microscale iron powder 

for the remediation of chlorinated organics in water. In addition, one company (Pars 

Environmental Inc.) has successfully used iron nanoparticles at several chromiumcontaminated sites for reducing soluble and carcinogenic chromium in the +6 valence 

state to insoluble and non-carcinogenic chromium in the +3 valence state. 

In general, nanoiron particles can treat the following contaminates in a range of 

geological settings: 

• Contaminants: 

o Halogenated aliphatics (PCE, TCE, 1,1,1-TCA, 1,1,2,2-TeCA) 

o Halogenated aromatics 

o PCBs 

o Halogenated herbicides and pesticides 

o Nitroaromatics 

o Metals (e.g., Cr6+, As) 

• Geologic Conditions: 

o Sand 

o Silt 

o Fractured rock 

o Landfills 

o Fill materials 

o Sediments 

Additionally, EPA is preparing a fact sheet on the use of nanotechnology for site 

remediation and will include information about sites where the technology has been 

tested. 

 

2.2.2 Description 

Iron nanoparticles represent the only field application of free-released nanoparticles for 

environmental remediation. First suggested in 1996 and now the subject of a number of 
33 

reviews (Kumar 2006, Zhang and Elliott 2006, Lo et al. 2006), the use of iron 

nanoparticles is a variation on the use of ZVI as a PRB. 

The non-nanoparticle ZVI PRB technology has been used to remediate contaminated 

groundwater for almost 20 years (Senzaki and Kumagai 1988) and has been demonstrated 

in the field and in the laboratory for a wide range of contaminants, including the 

reduction of nitrates, bromates, chlorates, nitroaromatic compounds, chlorinated ethanes, 

chlorinated methanes, and brominated or carbarylated pesticides, and the removal of 

arsenic, lead, uranium, mercury, and hexavalent chromium (Nuxoll et al. 2003, Arnold 

and Roberts 2000). Typically, iron filings or microscale iron powder have been used to 

create a barrier a few meters wide, contained by gravel supporting beds. The chemistry is 

well understood as the corrosion of iron based on the following reactions: 

 2Fe0

(s) + 4H+(aq) + O2(aq) → 2Fe2+(aq) + 2H2O(l) 

 Fe0

(s) + 2H2O(l) → Fe2+(aq) + H2(g) + 2OH−(aq)

 4Fe2+(aq) + 4H+

(aq) + O2(aq) → 4Fe3+(aq) + 2H2O(l) 

 2Fe2+(aq) + 2H2O(l) → 2Fe3+(aq) + H2(g) + 2OH−

(aq)

As ZVI is oxidized to ferrous and/or ferric iron, pH increases, hydrogen is evolved, 

oxidizable materials are consumed, and the strong reducing conditions created are 

favorable for the pathways (oxide-mediated electron transfer from the metal to the 

chlorinated organic, reduction of the chlorinated organic by the ferrous iron and reduction 

by evolved hydrogen)—leading to complete dechlorination. Eventually, ferric or ferrous 

iron may precipitate as a solid or remain in solution, depending on the pH and redox 

conditions. Mineral precipitates of carbonates, sulfides, and/or oxides may form coatings 

on the reactive grains, inhibit the performance of the iron, and reduce the porosity and 

permeability of the aquifer, but analysis of the evidence suggests that destruction of 

chlorinated solvents can still continue to completion. Additionally, the generation of 

strong reducing conditions and hydrogen gas foster anaerobic microbial growth and 

increase natural biological degradation in the field (Henn and Waddill 2006). 

The first field-scale application of conventional ZVI for groundwater remediation was at 

the Canadian Forces Base in Borden, Ontario in 1991. A treatment zone was excavated, 

isolated by sheet pile; filled with a mixture of granular iron and sand; and the sheet piles 

were removed. Contaminated groundwater flowed through the treatment zone and the 

chlorinated ethenes (perchloroethylene and trichloroethylene) were almost completely 

removed. The approach is now a standard, and regulatory guidance for the general use of 

PRBs (including those involving iron) is available (ITRC 1999a), together with design 

guidance (ITRC 1999b), and recently learned lessons and new directions (ITRC 2005). 

The concept of using nanoparticle iron to remediate chlorinated organics follows almost 

immediately from the conventional ZVI treatment. The small size of the particles (~10 

nm) would allow them to be injected into a geologic matrix and reach areas unavailable 

even to the microbes (~1,000 nm) used in bioremediation. Since reactivity appears to be 
34 

a direct function of total iron particle surface area, their performance is expected to be 

superior to that of larger particles. Production of ZVI nanoparticles is relatively easy, 

involving the reduction of ferric ion by sodium borohydride (Wang and Zhang 1997): 

 4Fe3+ + 3BH−

4 + 9H2O → 4Fe0

↓ +3H2BO−

3 + 12H+

 + 6H2

A successful, pilot-scale study has already been performed (Henn and Waddill 2006) 

using 300 pounds of palladium-catalyzed and polymer-coated nanoscale ZVI particle 

suspension at the Naval Air Station in Jacksonville, Florida. The particle suspension was 

injected via a gravity feed and recirculated through a source area containing chlorinated 

volatile organic compounds (VOCs). Between 65 and 99% aqueous-phase VOC 

concentration reduction occurred, due to abiotic degradation, within five weeks of the 

injection and then yielded to slower biological degradation. Aqueous-phase VOC 

concentrations were reduced up to 99 % and were near or below applicable regulatory 

criteria. Though there are still considerable knowledge gaps, the technology appears to 

have great potential. 

Recently, Pars Environmental, Inc. has developed a ZVI particle which, over time, 

encapsulates the metal contaminant; it is reported that this encapsulated layer 

immobilizes the contaminant for up to 30 years. This stepwise process resulting in the 

reduction of Cr(VI) to Cr(IV) and encapsulation of Cr(IV) in an onion-like skin around a 

nano ZVI particle is illustrated in Figure 1. 

Figure 1. Encapsulation stabilization of the contaminant 

1. ZVI

2. Adsorption of nano iron

3. Reduction of Cr(VI)

4. Formation of 

Cr-Fe alloy 

(hydroxide)
35 

The key features of this process as illustrated for Cr(IV) are: 

1. Nano Cr-Fe layer 

a. Thickness - 10 nm 

b. ~ 40 atoms 

2. 2/3 of the mass from Cr(VI) 

a. Cr 0.667 Fe 0.333 OOH 

3. Insoluble 

4. Reducing power (Fe0) 

The same reducing ability of ZVI is suggested for the remediation of radionuclides and 

heavy metals to bring about a reduction of the metal to a less soluble, lower oxidation 

state. For chromium, a conventional ZVI PRB consisting of 450 tons of granular ZVI was 

installed in 1996 at the United States Coast Guard Support Center in Elizabeth City, 

North Carolina, and has been subject to considerable documentation (Puls et al. 1998, 

Blowes et al. 1997, Blowes et al. 1999, FRTR 1998). The PRB was a continuous trench 

approximately 46 m long, 7 m deep, and 0.6 m thick. Concentrations of Cr(VI) had been 

as high as 5 mg/L, but decreased to non-detectable levels (<0.0025 mg/L) after 

installation of the PRB. The removal mechanism for Cr(VI) was determined to be 

precipitation as Cr(III) oxyhydroxide or co-precipitation with iron oxyhydroxide. Despite 

this success, a similar ZVI PRB at the Haardkrom site electroplating facility in Kolding, 

Denmark, was not effective, with speculation being that the TCE present may have 

depleted the chromium-reducing ability of portions of the barrier (Roehl et al. 2005). 

For uranium, a number of conventional ZVI barriers (Bronstein 2005) have been 

demonstrated, including: 

• Bodo Canyon Disposal Site, La Plata County, Colorado—a number of PRBs 

(composed of ZVI, copper wool, and steel wool) were used to treat arsenic, 

molybdenum, selenium, uranium, vanadium, and zinc. The barrier containing ZVI 

operated from August 1999 until June 2004 (when flow ceased from the seep and 

remediation was no longer needed). It maintained effluent uranium concentrations 

of less than 0.01 mg/L, and was highly effective in treating contaminants. 

• Cotter Corporation Uranium Mill, Cañon City, Colorado—a ZVI PRB was used 

to treat molybdenum and uranium. Though the barrier eventually failed for 

molybdenum, uranium concentrations remained at less than 0.006 mg/L. It was 

found that the ZVI was clogged by mineral precipitants. Modifications, including 

a pretreatment zone composed of coarse gravel and ZVI, were suggested. 

• Fry Canyon Site, Fry Canyon, Utah—a PRB of ZVI, amorphous ferric oxide 

(AFO), and phosphate rock was used to treat uranium. The ZVI barrier has been 

the most effective, removing 99.9% of uranium. 

• Mecsek Ore Site, Pecs, Hungary—a PRB composed of ZVI and shredded cast 

iron was used to treat uranium, and concentrations within the groundwater in 

2003 were reduced to less than 1% of the influent value after passing through the 

barrier. 
36 

• Monticello Mill Tailings Site, Monticello, Utah—a ZVI PRB was used to treat 

uranium, arsenic, manganese, molybdenum, selenium, vanadium, and nitrates. 

Results show that the barrier was effective in treating the contaminants. Nearly all 

of the uranium, arsenic, manganese, molybdenum, selenium, and vanadium were 

removed from the groundwater, and nitrate, molybdenum, and manganese were 

greatly reduced. Since 2000, contaminants have been reduced to below detectable 

levels. 

• Rocky Flats Environmental Technology Site (Solar Ponds Plume), Golden, 

Colorado—a barrier composed of ZVI and wood chips was used to treat nitrate 

and uranium. Remediation goals required a reduction of uranium from 20-28 

pCi/L to 10 pCi/L. Surface stream samples below 10 pCi/L for uranium indicate 

that the PRB is working properly. 

• Y-12 Site, Oak Ridge, Tennessee—a barrier composed of ZVI and peat materials 

is being used to treat uranium, technetium, and nitric acid. A funnel and gate 

barrier failed due to leaking. A continuous trench was subsequently installed and 

has shown that uranium and technetium concentrations have decreased, but 

because of reactions with groundwater constituents, the lifespan of the ZVI wall 

may be significantly shorter than expected. 

Overall, these results strongly support the case for using conventional ZVI as an effective 

reductant for radionuclides, such as uranium. Thus, the potential for iron nanoparticles is 

considerable. Extensive research is ongoing, including studies on formulation of the iron 

nanoparticles, delivery vehicles and methods of in-situ stabilization. A potential remedial 

scheme using ZVI nanoparticles is shown in Figure 2. 

Figure 2. Potential remedial scheme using ZVI nanoparticles 

Obviously, a considerable amount of further work must be performed to establish 

baseline performance and to develop the knowledge base required to gain regulatory 
37 

acceptability for the technology as applied to uranium. However, iron nanoparticles 

remain a leading contender for application to the remediation of radionuclides. 

 

 

2.2.3 Summary of Environmental Potential 

ZVI nanoparticles are the first field application of free-released nanoparticles for 

environmental remediation. The use of macro-scale ZVI in subsurface PRBs is a wellestablished technology for the reduction of both chlorinated hydrocarbons and toxic 

metals in contaminated ground water; ZVI nanoparticles use exactly the same chemistry, 

but take advantage of the increased surface area and the rheological ability of 

nanoparticles to flow in the subsurface and permeate crevices where contaminants may 

reside. The technology is potentially applicable in most circumstances where macro-scale 

ZVI would be employed. Where mixed contaminants, such as chlorinated organics and 

higher valency toxic metals, are present, ZVI nanoparticles may be able to accomplish 

the remediation of both types of material. The demonstrated ability of ZVI to encapsulate 

a heavy metal contaminant (chromium) through a combination of adsorption and 

reduction processes, and the ability of ZVI to act as a reducing agent offers significant 

potential for the remediation of radioactive species such as uranium or plutonium where 

the reduced form of the metal is of much lower solubility and can be effectively removed 

from solution. Risk issues are not expected to be significant since data, to date, show that 

the iron nanoparticles do not travel extensively, and nanoparticles of iron oxides (into 

which nanoparticulate iron will eventually transform) are ubiquitous in groundwater. 

2.2.4 References

Arnold, W.A., and A.L. Roberts. 2000. Pathways and kinetics of chlorinated ethylene and 

chlorinated acetylene reaction with Fe(0) particles. Environmental Science & 

Technology. 34: 1794-1805. 

Blowes, D.W., C.J. Ptacek, J.L. Jambor. 1997. In situ remediation of Cr(VI) 

contaminated groundwater using permeable reactive walls: Laboratory studies. 

Environmental Science and Technology. 31 (12): 3348-3357. 

Blowes, D.W., R.W. Puls, R.W. Gillham, C.J. Ptacek, T. Bennett, J.G. Bain, C.J. HantonFong, C.J. Paul. 1999. An In situ Permeable Reactive Barrier for the 

Treatment of Hexavalent Chromium and Trichloroethylene in Ground Water: 

Volume 2 Performance Monitoring. EPA/600/R-99/095b. Cincinnati, OH: United States 

Environmental Protection Agency. 

Bronstein, Kate. 2005. Permeable Reactive Barriers for Inorganic and Radionuclide 

Contamination. Prepared for U.S. EPA, Washington DC. Website. Accessed October 

2007. http://clu-in.org/download/studentpapers/bronsteinprbpaper.pdf. 
38 

Federal Remediation Technologies Roundtable (FRTR). 1998. In Situ Permeable 

Reactive Barrier for Treatment of Contaminated Groundwater at the U.S. Coast Guard 

Support Center, Elizabeth City, North Carolina. Website. Accessed October 2007. 

http://costperformance.org/profile.cfm?ID=287&CaseID=287. 

Henn, K.W. and D.W. Waddill. 2006. Utilization of nanoscale zero-valent iron for source 

remediation-A case study. Remediation Journal. 16(2): 57-77. 

 

Interstate Technology & Regulatory Council (ITRC). 1999a. Regulatory Guidance for 

Permeable Reactive Barriers Designed to Remediate Chlorinated Solvents, 2nd Edition,

PBW-1. Washington, DC: ITRC Permeable Reactive Barriers Team. 

ITRC. 1999b. Design Guidance for Application of Permeable Reactive Barriers for 

Groundwater Remediation, PBW-2. Washington, DC: ITRC Permeable Reactive Barriers 

Team. 

ITRC. 2005. Permeable Reactive Barriers: Lessons Learned/New Directions, PRB-4.

Washington, DC: ITRC Permeable Reactive Barriers Team. 

Kumar, C.S.S.R. 2006. Nanomaterials: Toxicity, Health and Environmental Issues.

Wiley-VCH, Germany. 

Lo, I.M.-C., R.Y. Surampalli, and K.C.K. Lai (Eds.). 2006. Zero-Valent Iron Reactive 

Materials for Hazardous Waste and Inorganics Removal. ASCE Publications, Reston, 

VA. 

Nuxoll, E.E., T. Shimotori, W.A. Arnold, E.L. Cussler. 2003. Iron Nanoparticles in 

Reactive Environmental Barriers. Presentation at the AIChE Annual Meeting, November 

20, 2003. 

Puls, R. W., D.W. Blowes, R.W. Gillham. 1998. “Emplacement verification and longterm performance monitoring of a permeable reactive barrier at the USCG Support 

Center, Elizabeth City, North Carolina.” In Groundwater quality: remediation and 

protection, Vol. 250. M. Herbert, and K. Kovar, eds. Amherst, Mass: International 

Association of Healthy Soils Publication, 459-466. 

Roehl, K.E., K. Czurda, T. Meggyes, F. Simon, D.I. Stewart. 2005. Long-term 

Performance of Permeable Reactive Barriers. Elsevier, New York. 

Senzaki, T. and Y. Kumagai. 1988. Treatment of 1,1,2,2-Tetrachloroethane with iron 

powder. Kogyo Yosui. 357(1): 2-7. 

Wang, C. and W. Zhang. 1997. Nanoscale metal particles for dechlorination of PCE and 

PCBs. Environmental Science and Technology. 31(7), 2154-2156. 

Zhang, W.-X. and D.W. Elliott. 2006. Applications of iron nanoparticles for groundwater 

remediation; Remediation Journal. 16(2): 7-21.
39 

2.3 Self-Assembled Monolayers on Mesoporous Supports 

SAMMS is an award-winning (PNNL 2007) hybrid of two active areas in materials 

science—mesoporous materials and molecular self-assembly on the mesoporous material 

surface—that combine to create a material capable of efficiently removing target species 

from aqueous solutions and other liquids. 

A highly developed, engineering-scale technology that is entering the market, SAMMS 

reached the commercial threshold in 2006 for mercury remediation. The conceptual 

developer, Pacific Northwest National Laboratory (PNNL) states that currently 

demonstrated laboratory production capacity is approximately 5 kg. Battelle (the operator 

of PNNL) and Mobil Oil Corporation (developer of the original mesoporous support, 

now ExxonMobil) are establishing commercial production capacity for the manufacture 

of these materials. Mobil has demonstrated the ability to produce mesoporous substrates 

in batch quantities of one ton or more; scale-up of the functionalization process to these 

production levels is underway. Costs for these materials are expected to fall into the 

range of selective anion ion exchange resins. PNNL maintains a Web site devoted to 

SAMMS. In addition to excellent descriptions of the technology (SAMMS 2006), the 

Web site provides links to information on: 

• current R&D activities; 

• publications; 

• general articles; 

• lanthanide and actinide investigations; and 

• Other forms (thiol, chelate, anion, and actinide) of SAMMS. 

The following descriptions have drawn heavily from the information contained in the 

PNNL Web site and its links. 

2.3.1 Description 

Mesoporous materials, one component of the SAMMS hybrid, are porous substances 

with pore diameters in the range of 2-50 nm; materials below this size range are called 

“microporous” (and usually include materials such as zeolites, aluminophosphates 

(AlPOs), clathrasils, pillared and non-pillared clays) and above this range they are called 

“macroporous”. Mesoporous materials are thus within the 1-100 nm length scale that 

typically defines nanotechnology. The term “mesoporous” can apply to any material with 

pore size in the appropriate range, but in the case of the SAMMS technology, structured 

mesoporous ceramics are usually involved. In 1992, researchers at Mobil, while 

exploring novel microporous materials for new catalysts, synthesized a new type of 

silica-based material, named the M41S family, which possessed uniform, mesoporousscale pores regularly distributed throughout the solid material. The synthesis used 

cylindrical surfactant micelles to direct (create) the structure formation of the pores in the 

sol-gel preparation process. The larger pores allow bulk solution to enter and easily 

explore the interior’s entire surface; this is in contrast to the behavior of the smaller pores 
40 

typical of zeolites (typically 0.5-1 nm), where size exclusion is often a dominant effect. 

Fryxell (SAMMS 2006) has described the structure as follows: 

"To envision what mesoporous ceramic look like, think of a glass honeycomb 

in which the holes in the honeycomb are very uniform and are only 60 

Angstroms across (roughly twice the width of a double-helix strand of DNA), 

and the walls are only 10 Angstrom thick (about the size of a "typical" amino 

acid molecule). These parallel, open-ended pores result in a material that has 

extremely high surface area, all of which is accessible to solution." 

SAMMS are created by attaching a monolayer of molecules to mesoporous ceramic 

supports. The method uses linear molecules possessing different chemical functionalities 

at each end. The chemical functionality at one end has an affinity for the mesoporous 

surface, while the chemical functionality at the other end has an affinity for the target 

species to be bound by the SAMMS material. A combination of intermolecular and 

intramolecular forces drive the bi-functional molecules to assemble along the entire 

length of the pore as a close-packed monolayer, completely covering the surface of the 

mesoporous support, thus exposing a new chemical surface and interface to bulk solution. 

Figure 3 (SAMMS 2006) presents a graphical representation of the process. 

Figure 3. Formation of SAMMS 

Possessing physical characteristics similar to activated carbon, mesoporous materials 

have very high surface area to mass ratios. SAMMS powder can have a specific surface 

area of approximately 1000 m2

/g. For comparison, the surface of a tennis court is 

approximately 260 m2

. Monolayer molecules fully cover the available surface and thus 

present a large area for binding target species. The large surface area, combined with 

large pore sizes that allow entry of solution, create a hybrid material with fast kinetics, 

high material loading, and excellent selectivity. Both the properties of the molecules in 

the monolayer and the pore size of the mesoporous support can be tailored for a specific 
41 

application. The functional group facing the interior of the pore can be designed to 

selectively bind targeted molecules while the pore size, monolayer length, and density 

can be adjusted to give the material specific diffusive and kinetic properties. 

SAMMS is developing in several engineered forms (such as beads, membranes, and 

membrane cartridges) and can be delivered with a variety of chemically active 

substances. In addition, the SAMMS technology is developing systematically in a 

number of functional forms including: 

• Thiol-SAMMS, primarily targeting Hg, Ag, Au, Cu, Cd, and Pb;

• Chelate-SAMMS, primarily targeting Cu, Ni, Co, and Zn; 

• Anion-SAMMS primarily targeting chromate, arsenate, selenite, and 

pertechnetate; and 

• Actinide-SAMMS primarily targeting Am, Pu, Th, Np, and U. 

a. Thiol-SAMMS. Thiol-SAMMS was the first and is the most extensively 

investigated functional form, having been specifically developed for the removal of 

mercury from liquid media (Chen et al. 1999, Mattigod et al. 1997). Thiol-SAMMS 

is also the first commercial application of the SAMMS technology 

(ChemicalProcessing.com 2006). The Thiol-SAMMS functional form takes 

advantage of the fact that the thiol functional group has a very strong affinity for 

mercury (in fact “mercaptans”, an alternate name for thiols, derives from the Latin 

“mercurium captans,” meaning mercury capturers). In Thiol-SAMMS, a monolayer 

of mercaptopropyl siloxane coats the mesoporous surface with the thiol groups 

pointing towards the pore center, presenting a thiol surface to the solution in the 

lined pores. This surface is able to bind cationic, organic, metallic, and complexed 

forms of mercury with great affinity (distribution coefficient, or Kd, ~1 x 108) and 

rapid kinetics. A graphical representation is shown in Figure 4. 

Figure 4. Thiol-SAMMS showing mercury atoms (blue) binding to sulfur atoms 

(yellow) from thiol groups 

b. Chelate-SAMMS. In Chelate-SAMMS (SES 2007, SAMMS 2006), chelating 

functional groups (such as ethylenediamine, ethylenediamine triacetic acid, pyridine, 

etc.) are attached to the surface of the mesoporous materials using a similar chemistry 
42 

to that used for preparation of the thiol-SAMMS. The chelating group is tailored for 

the targeted metal (e.g., ethylenediamine for copper and 1,2-hydroxypyridinone 

(HOPO) for the actinides). Results are promising and research is continuing to 

optimize the synthesis and metal loadings. 

An intriguing aspect of Chelate-SAMMS, and one that demonstrates the versatility of 

the technology, is through a synthesis modification, which is a functional form of 

SAMMS that is able to bind cesium (Lin et al. 2001). The basis is that metal 

ferrocyanides have been widely investigated as ion exchangers for cesium, with 

potassium cobalt ferrocyanide having the advantages of high capacity and selectivity 

for cesium, but the drawback of being a very fine powder that is difficult to coax into 

an effective engineered form. In the SAMMS approach, mesoporous silica is 

functionalized with an ethylenediamine terminated silane. Copper(II) ions are then 

incorporated simply by stirring a copper(II) chloride solution with the functionalized 

mesoporous support for a few hours, and refluxing in toluene to produce Cu-EDASAMMS. This is converted to Cu-Ferrocyanide-EDA SAMMS simply by mixing CuEDA-SAMMS with sodium ferrocyanide. The conclusion of the work was that: 

“The synthesis of the cesium selective SAMMS is a simple, direct, and 

convergent synthesis. These nanocomposite materials are easily made from 

commercially available bulk materials and are highly selective for cesium from 

various high-salt and acid solutions. The high surface area of the mesoporous 

silica creates a high loading capacity for cesium sorption. The fast binding 

kinetics and high loading capacity of SAMMS sorbent materials are due to the 

rigidly open pore structure and rapid interfacial chemistry. The chemical 

specificity results from the selectivity of the copper(II) ferrocyanide interface 

within the nanoporous structure. This unique combination of properties makes 

SAMMS-based methodology a strong candidate for the cleanup of cesiumcontaining nuclear wastes and contaminated groundwater” (Lin et al. 2001). 

c. Anion-SAMMS. Anion-SAMMS functional forms (SAMMS 2006, SES 2007) are 

being investigated since there is a great need for effective anion binders (e.g., in the 

cleanup of pertechnetate contamination at DOE sites). While organic ion exchange 

resins based on quaternary ammonium ion exchange chemistry and inorganic 

materials, such as alumina, are available, they are orders of magnitude less effective 

than state-of-the-science cation exchangers. The SAMMS approach mimics the 

strategy used for Cu-Ferrocyanide-EDA SAMMS by lining the pores of the 

mesoporous material with cationic transition metals complexes specifically targeting 

those complexes that would allow for a direct interaction between the cationic 

receptor and the target anion. Research (Fryxell 2001) has shown that copper or 

nickel ethylenediamine complexes immobilized on mesoporous silica are extremely 

efficient ion binding materials for chromate, comparable in terms of loading to the 

best cation exchangers. By exploiting variations in transition-metal complex 

chemistry, the promise is held that effective ion exchangers for tetrahedral anions can 

be developed. It is also worthy of note that Thiol-SAMMS capped with soft metals, 
43 

such as silver or mercury, have shown promise as “getters” for radioiodine (Mattigod 

et al. 2003a, Mattigod et al. 2003b). 

d. Actinide-SAMMS. Actinide-SAMMS (Fryxell 2001, Lin et al. 2005, SAMMS 

2006, SES 2007) is the least developed area of the SAMMS technology. There exists 

a body of research on SAMMS applied to lanthanide separations (Fryxell 2001, 

Fryxell 2004, Yantasee 2005, Lin et al. 2005), and parallels between lanthanide 

chemistry and actinide chemistry are fairly well understood. In addition, the 

theoretical basis has been explored (Fryxell 2001) and laboratory experiments suggest 

that by examining potent actinide binding ligands from prior studies and synthesizing 

functional forms such as amidophosphonic acid-SAMMS and hydroxypyridinoneSAMMS, excellent actinide sorbents can be developed. 

At the present time no studies have been conducted on the fate and transport of SAMMS 

material. 

2.3.2 Operational Considerations 

PNNL staff assert that SAMMS is clearly superior to commercially-available sorbents, 

with 99% of Thiol-SAMMS’ mercury-adsorbing action taking place in the first five 

minutes; tests at PNNL show that the material can remove 99.9% of mercury in a 

simulated wastewater, reducing the mercury level to well below EPA discharge limits 

(ChemicalProcessing.com 2006). Treatment costs appear to be an order of magnitude 

lower than those of the best available alternative technologies. 

From ChemicalProcessing.com: “...says Shas Mattigod, a staff scientist at PNNL. ‘There 

is no comparison.’ Mattigod calls treatment costs an order of magnitude lower than those 

of the best available alternative technologies. ‘We estimate that it will cost about $200, 

including material, analysis and labor, to treat similar volumes of this waste solution,’ he 

says. ‘This would save $3,200 over the more-traditional disposal methods.’” 

2.3.3 Summary of Environmental Potential 

The SAMMS technology is one of the most promising nano-enabled environmental 

technologies. It is probably the only nanotechnology so far that was both specifically 

designed for, and has already found commercial application in, environmental 

management. It is a technology used for separating aqueous solutions, but is more likely 

to find application in sorbent units as opposed to being released into the environment to 

perform its separatory behavior. Technologically, it combines rational ligand design for 

targeting species in solution with molecular self assembly on mesoporous support 

structures. Rational ligand design is well understood; molecular self assembly and 

mesoporous material behavior are firmly enough understood to allow commercial 

application. Yet both are benefiting greatly from further developments, many coming 

from various areas of nanotechnology research. The technology is extremely flexible, 

allowing a wide variety of aqueous species to be targeted for removal. The SAMMS 

material offers the benefit of high capacity, and also appears to be a strong candidate as a 
44 

waste form that may be disposed of directly, thus significantly easing further processing 

requirements. 

2.3.4 References 

ChemicalProcessing.com. “Nanosponge soaks up mercury”. 2006. Website. Accessed 

October, 2007. http://www.chemicalprocessing.com/industrynews/2006/052.html. 

Chen, Xiaobing, X. Feng, J. Liu, G. Fryxell, M. Gong. 1999. Mercury Separation and 

Immobilization using Self-Assembled Monolayers on Mesoporous Supports (SAMMS). 

Separation Science and Technology. 34 (6-7):1121-1132. 

Fryxell, G.E. 2001. Actinide-Specific Interfacial Chemistry of Monolayer Coated 

Mesoporous Ceramics Number 65370. FINAL REPORT U.S. Department of Energy 

Environmental Management Science Program. Website. Accessed October 2007. 

http://www.osti.gov/em52/2000projsum/65370.pdf. 

Fryxell, G E, H. Wu, Y. Lin, W.J. Shaw, J.C. Birnbaum, J.C. Linehan, Z. Nie, K. 

Kemner, S. Kelly. 2004. Lanthanide selective sorbents: self-assembled monolayers on 

mesoporous supports (SAMMS). Journal of Materials Chemistry. 14 (200): 3356-3363. 

Lin, Y., G. Fryxell, H. Wu, M. Engelhard. 2001. Selective Sorption of Cesium Using 

Self-Assembled Monolayers on Mesoporous Supports. Environmental Science 

Technology. 35(19): 3962 -3966. 

Lin, Y., S.K Fiskum, W. Yantasee, H. Wu, S.V. Mattigod, G.E. Fryxell, K.N. Raymond, 

J.Xu. 2005. Incorporation of Hydroxypyridinone (HOPO) Ligands into Self-Assembled 

Monolayers on Mesoporous Supports (SAMMS) for Selective Actinide Sequestration. 

Environmental Science and Technology. 39:1332-1337. 

Mattigod, S. V., Feng, X., Fryxell, G. E., Liu, J., Gong, M., Ghormley, C., Baskaran, S., 

Nie, Z., Klasson, K. T. 1997. Mercury Separation from Concentrated Potassium 

Iodide/Iodine Leachate Using Self-Assembled Mesoporous Mercaptan Support 

(SAMMS) Technology. PNNL-11714. Prepared for the U.S. DOE, Washington DC. 

 Mattigod, S.V., R. Skaggs, G.E. Fryxell. 2003a. Removal of Heavy Metals from 

Contaminated Waters Using Novel Nanoporous Adsorbent Materials. PNWD-SA-5955, 

Battelle, Pacific Northwest Division, Richland, WA. 

Mattigod, S. V., G. E. Fryxell, R. J. Serne, K. E. Parker, F. M. 2003b. Evaluation of 

Novel Getters for Adsorption of Radioiodine from Groundwater and Waste Glass 

Leachates. Radiochimica Acta. 91: 539-545. 

Pacific Northwest National Laboratory (PNNL). R&D100 Awards. Website. Accessed 

October, 2007. http://www.pnl.gov/about/rd100awards.asp. 
45 

Self Assembled Monolayers on Mesoporous Supports (SAMMS). 2006. Website. 

Accessed October, 2007. http://samms.pnl.gov. 

 

 Steward Environmental Solution (SES). 2007. Website. Accessed November 2007. 

http://www.stewardsolutions.com. 

Yantasee W., G.E. Fryxell, Y. Lin, H. Wu, K.N. Raymond, J. Xu. 2005. 

Hydroxypyridinone (HOPO) Functionalized Self-Assembled Monolayers on Mesoporous 

Supports (SAMMS) for Sequestering Rare Earth Cations. Journal of Nanoscience and 

Nanotechnology. 5(4): 527-535. 
46 

2.4 Membranes: Nanofiltration and Affinity 

2.4.1 Background 

The term “membrane” covers a wide range of processes, including those used for gas/gas, 

gas/liquid, liquid/liquid, gas/solid, and liquid/solid separations. Membrane technology is 

well-established and is used in many processes. Membrane production is a large-scale 

operation. Membranes are used for the separation of radionuclides as well as other 

contaminants. This section discusses three nanotechnologies that are often used in the 

filtering processes and show great potential for applications in remediation. 

1. Nanofiltration (and its sibling technologies: reverse osmosis, ultrafiltration, and 

microfiltration), is a fully-developed, commercially-available membrane 

technology with a large number of vendors. Nanofiltration relies on the ability of 

membranes to discriminate between the physical size of particles or species in a 

mixture or solution and is primarily used for water pre-treatment, treatment, and 

purification (Van der Bruggen and Vandecasteele 2003, Rautenbach and Groeschl 

1990, Rautenbach et al. 1997, Atkinson 2002, Costa and de Pinho 2006). There 

are approximately 600 companies worldwide offering membrane systems. 

2. Electrospinning is a process utilized by the nanofiltration process, in which fibers 

are stretched and elongated down to a diameter of about 10 nm. The modified 

nanofibers that are produced are particularly useful in the filtration process as an 

ultra-concentrated filter with a very large surface area. Studies have found that 

electrospun nanofibers can capture metallic ions and are continually effective 

through re-filtration. 

3. Surface modified membrane is a term used for membranes with altered makeup 

and configuration, though the basic properties of their underlying materials 

remain intact. 

With the global water market valued at over $300 billion, and water supplies becoming 

an important international issue, nanofiltration is anticipated to have a very important role 

in the future. In contrast to the types of filtration that rely on size discrimination, affinity 

membranes use chemical recognition between the components of the membrane and 

components of solution to effect separation. Affinity membranes and related technologies 

are well-established and find their primary markets in the biomedical and biotechnology 

industries. 

2.4.2 Nanofiltration Membranes 

Nanofiltration is one of a group of similar membrane processes (including reverse 

osmosis, ultrafiltration, and microfiltration) used to separate components of a liquid 

mixture. These four processes are best understood together and as a continuum in terms 

of the size of particles that can be removed from a mixture. 
47 

In the regular particle filtration of a liquid containing entrained particles, the liquid 

mixture is forced (by gravity or applied pressure) through a filter medium that has pores 

or passages of a size that allows the liquid and small particles to pass through, but 

prevents passage of larger particles. A paper coffee filter is an example of a regular 

particle filtration. The paper filter allows passage of the water containing dissolved or 

extremely small material, but prevents passage of the larger coffee grounds. Smaller 

pores or passages in the filter medium prevent larger particles from passing through with 

the liquid. Figure 5 provides a graphical representation of the generalized filtration 

process. 

Figure 5. General representation of the filtration process 

There are two basic types of filters: depth filters and membrane filters. Depth filters have 

a significant physical depth and the particles to be retained are captured through out the 

depth of the filter. Depth filters often have a labyrinthine three-dimensional structure, 

with multiple channels and heavy branching so that there is a large pathway through 

which the liquid must flow and by which the filter can retain particles. Depth filters have 

the advantages of low cost, high throughput, large particle retention capacity, and the 

ability to retain a variety of particle sizes. However, they can suffer from entrainment of 

the filter medium, uncertainty regarding effective pore size, some uncertainty regarding 

the overall integrity of the filter, and the risk of particles being mobilized when the 

pressure differential across the filter is large. 

The second type of filter is the membrane filter, in which depth is not considered 

important. The membrane filter uses a relatively thin material with a well-defined 

maximum pore size and the particle retaining effect takes place almost entirely at the 

surface. Membranes offer the advantage of having well-defined effective pore sizes, can 

be integrity tested more easily than depth filters, and can achieve more filtration of much 

smaller particles. They tend to be more expensive than depth filters and usually cannot 

achieve the throughput of a depth filter. Filtration technology has developed a welldefined terminology that has been well addressed by commercial suppliers; the American 

Standard Test Method (ASTM) has developed a standard (ASTM D6161-05) (ASTM 
48 

2007) that addresses the terminology used for microfiltration, ultrafiltration, 

nanofiltration, and reverse osmosis membrane processes. 

Reverse osmosis, nanofiltration, ultrafiltration, and microfiltration are all membrane 

processes able to remove small particles or soluble species. They all work on exactly the 

same principle as regular particle filtration, but the distinguishing feature between them is 

their effective pore size, and thus, the minimum size of particle that will be rejected by 

the membrane; reverse osmosis membranes reject all but the very smallest species (small 

soluble organic species that are not otherwise considered even to be “particles”), while 

microfiltration allows considerably larger particles to pass through. Figure 6 provides a 

graphic representation of the process characteristics of the four membrane processes, and 

Figure 7 provides a graphic representation showing the size range and approximate 

molecular weight range where each of the four membrane filtration technologies finds its 

application. 

Regular particle filtration will reject particles down to about the one micron (1,000 nm) 

size range. If filtration to reject particles smaller than this limit is required, microfiltration 

should first be considered. Microfiltration operates at the low end of familiar particle 

filtration, being at the limit able to retain particles above the 100 nm size range. Its 

separating abilities thus cease at the 100 nm limit usually associated with 

nanotechnology. Microfiltration can remove most suspended solids and living material, 

such as bacteria, but will not retain any type of dissolved solute or smaller biological 

material, such as viruses. Ultrafiltration is effective only to the 10 nm size range, 

allowing it to reject most proteins, viruses, and groundwater colloids. Nanofiltration is 

usually used to remove material in the 0.5-10 nm range and will reject most of the larger 

organic molecules, sugars, and multivalent ions, with only monovalent ions and water 

being able to pass through. To remove the monovalent ions, reverse osmosis membranes 

are required; these will reject almost all material, except water and simple organic species 

(such as very short chain alcohols and acids). 

Figure 6. Membrane process characteristics 
49 

Figure 7. Size range for filtration separation processes 

Benefits of water treatment nanofiltration include: 

• Lower operating costs, 

• Lower energy costs, 

• Lower discharge and less wastewater than reverse osmosis, 

• Reduction of total dissolved solids (TDS) content of slightly brackish water, 

• Reduction of pesticides and VOCs (organic chemicals), 

• Reduction of heavy metals, 

• Reductions of nitrates and sulfates, 

• Reduction color, tannins, and turbidity, 

• Hard water softening, 

• Being chemical-free (i.e., does not use salts or chemicals), and 

• Water pH after nanofiltration is typically non aggressive. 

For radionuclide treatment applications, nanofiltration and ultrafiltration have been 

investigated as an ultra low-level analytical tool to separate actinides from other ionic 

species in high-level radioactive waste solutions, and as a possible treatment option for 

waste streams from the Los Alamos National Laboratory Plutonium Treatment Facility 

(Smith 1993). In these applications, the nanofiltration and ultrafiltration membranes are 

coupled with water-soluble chelating polymers (WSCP). WSCPs are polymers 

engineered to contain both highly selective chelating functionalities to bind with targeted 

metal ions, and solubilizing functionalities to allow the polymer to dissolve in water 

(Smith et al. 1995). The polymer’s overall size is large enough that it exceeds the 

rejection limit for an ultrafiltration membrane. When the unchelated polymer is 

introduced into a solution that contains the target ions for which the chelating groups 
50 

were designed, the polymer binds with these target ions and nothing else. The chelated 

polymer can then be separated from the solution (and all other ions in the solution) by 

ultrafiltration; the chelated target ions can be separated from the polymer by adjusting the 

solution chemistry; and the regenerated water-soluble chelating polymer can be recycled 

(Jarvinen 1995). In these applications, ultrafiltration combined with WSCP has the 

advantage of being aqueous-based (such as ion exchange resins), has a high throughput 

and rapid kinetics (like two-phase liquid-liquid extraction systems), but does not have the 

disadvantage of using organic solvent-based extractants.

WSCPs with molecular weights in the 100,000 range have been prepared based on 

polyacrylic acid or polyethyleneimine with functional groups of phosphonic acid, 

acylpyrazolone acid, and hydroxamic acid. In acidic nitrate and acidic chloride solutions, 

these functional groups have a high affinity for actinides and a low affinity for alkali 

metals and alkaline earths. The concentration of polymer is typically 1-2%, with the 

ultrafiltration membrane typically having 10-100 μm pores (Gibson 1994, Smith 1993). 

This technology has been tested at bench scale for the removal of heavy metal ions from 

electroplating waste streams. Development continues (Moreno-Villoslada and Rivas 

2002, Rivas et al. 2003, Rivas et al. 2006, Tomida et al. 1994, Kawano et al. 2002), 

though dendrimers may compete as a chelating moiety in the future if their costs 

decrease. 

Summary of Environmental Potential 

 

Nanofiltration is an established technology with numerous equipment developers, 

manufacturers, and vendors. The major application is in reverse osmosis for desalination 

and production of high purity water for specialized industrial uses, with small 

applications for wastewater treatment. While current and past development has relied 

predominantly on size exclusion effects, the promise of nanotechnology is that specific 

chemical and physical behavior can be engineered into the materials, and that the slow 

flow rates typical of reverse osmosis and nanofiltration can be overcome—allowing the 

energy requirements and production costs for the production of pure water to be greatly 

reduced. The general industrial uses of filtration technology should support developments 

that will allow spin-off applications for environmental uses; a significant effort is being 

made to apply nanotechnology developments of filtration technology to the production of 

potable water in economically challenged arid regions. The primary environmental 

applications are likely to be “end-of-pipe” and polishing uses. Nanofiltration combined 

with water-soluble chelating polymers has been investigated for the removal of 

radioactive species from aqueous waste streams (Smith 1993, Smith et al. 1995). 

 

2.4.4 Electrospun Fibers 

Electrospinning is a process for making nanofibers with diameters down to about 10 nm. 

The technology produces the nanofibers from polymer solutions or melts, with the 

extreme elongation and narrowing of the fiber occurring as a result of electrostatic 

repulsion. Electrospinning has the characteristics of both the commercial electrostatic 

spraying technique and the commercial spinning of fibers, each of which is a long 

established technology in its own right. Electrostatic spraying is a coating technology, 
51 

over a century old, involving atomizing a liquid from a spray gun and imparting an 

electrical charge to the droplets by using an electrode placed at the end of a spray gun. 

The electrode typically operates in the 30 to 140 kilovolt range with a current of 0 to 225 

microamperes. The droplets are attracted toward a target that is either grounded or has a 

positive charge, and produces a uniform coating of liquid (frequently paint). The 

electrostatic spraying approach can also be used as a surface modification technique to 

introduce nanoparticles onto fibers or other surfaces by spraying solutions that contain 

only about one particle per droplet. 

In comparison, electrospinning (first patented by Antonin Formhals in 1934) uses the 

electrical charge to form a mass of fine polymer filaments. In electrospinning, a polymer 

solution or melt is driven through a spray gun nozzle and forms a droplet at the tip. When 

the voltage is applied to the nozzle, the droplet is stretched; if the viscosity of the material 

is sufficiently high, the breakup encountered in electrostatic spraying does not occur. 

Instead, a thin, charged liquid jet is formed. The jet elongates and is whipped 

continuously by electrostatic repulsion, forcing it to follow a spiral path toward the 

oppositely charged or grounded collector. The whipping action helps to elongate the jet 

much further to a diameter on the order of tens of nanometers. Figure 8 illustrates the 

basic process. Fibers are formed either by the melt cooling or the solvent evaporating 

from the polymer solution. Nanoparticles can be mixed into, or produced directly in, the 

polymer solution and spun with the fibers (Lee et al. 2005). Nanofibers produced in this 

way have many potential applications, including high efficiency filter media, as 

nanocomposite materials for water treatment membranes, catalysis, hydrogen storage, or 

in biomedical applications (such as drug release carriers or artificial tissue). 

Figure 8. Basic principle of electrospinning 
52 

Investigations into the potential of electrospun fibers for water treatment have mainly 

focused on their use in membranes, where the massive surface area (illustrated in Figure 

9) offers special advantages. Ki et al. (Ki et al. 2007) examined membranes of a 

nanofibrous blend of silk fibroin and wool keratose and found that it had an exceptional 

performance for the adsorption of metal ions, that its adsorption capacity was maintained 

after several desorption and re-adsorption cycles, and that it is very suitable for removing 

and recovering heavy metal ions from water, potentially as an affinity membrane. 

Ramakrishna et al. (Ramakrishna et al. 2006) reviewed electrospun nanofibers from the 

perspective that their porous nature and large surface-to-volume ratio gives them the 

potential for use in various applications where high porosity is desirable. They noted that 

electrospinning has an advantage of comparatively low cost with relatively high 

production rate, that the unique ability to produce nanofibers of different materials in 

various fibrous assemblies, and that the ability to form porous fibers means that the 

surface area of the fiber mesh can be increased tremendously. Since the fibers can be 

surface functionalized, affinity membranes can easily be formed with the potential for 

application in the removal of heavy metals from wastewater. They concluded that 

electrospinning may well be one of the most significant nanotechnologies of the 21st

century. 

Figure 9. An electrospun polysulphone membrane: (a) surface; 

(b) cross-section; and (c) magnified cross-section images 

Sang et al. (Sang et al. 2008) examined various filtration modes for using an electrospun 

chloridized polyvinyl chloride nanofiber membrane (including static adsorption, direct 

filtration, soil-addition filtration, diatomite-addition filtration, and micellar enhanced 

filtration), and they concluded that the membrane, when used with micellar enhanced 

filtration, can be used for the treatment of the groundwater containing heavy metals (such 

as copper, lead, and cadmium) with high efficiency. 

2.4.5 Surface Modified Membranes 

Electron-beam-induced grafting is one of two methods in the category of ionizing 

radiation—gamma radiation from cobalt-60 is the other. Electron-beam-induced 

technology provides a pathway for customizing surfaces such as membranes; hence, the 

commercial name eMembranes (developed by the Japan Environmental Purification 

Research Institute). The technology allows membrane surface alternation without 
53 

changing the basic properties of the underlying bulk materials. Electron-beam machines 

are currently available and play a significant role in processing specialty polymeric 

materials. For example, electron-beam-induced grafting has existed in some form for 

decades; nuclear power plants have used ion exchange resins enhanced by electron-beaminduced grafting to cleanse uranium from coolants. The future materials generated with 

this technology is based on over 50 years of scientific research. The technology is 

stimulating the development of new and promising membranes. Electron-beam-induced 

grafting is being used by laboratories throughout the world to create surfaces, including 

chemical resistance, wet ability, biocompatibility, antithrombo, dyability, and antistatic 

properties. Grafting has also been used to produce ion exchange membranes for the 

removal of heavy-metal for aqueous waste streams. An emerging application is biological 

separations, but the basic concept also has targeted the removal of heavy metals from 

industrial wastewaters. There is little doubt that many new and improved products will be 

created to aid in the cleanup of radionuclides. 

eMembrane technology is being extended to create specialized membranes for many 

potential applications. The ability to create specialized nano-engineered membranes 

opens up many envisioned possible future applications. An example of developing 

applications is a new water remediation technology, which could remove—in one pass—

multiple contaminants such as viruses, radionuclides, heavy metals, and chlorinated 

solvents. A membrane could be tailored for a specific cleanup application. This would 

greatly reduce remediation costs and accelerate the cleanup process. 

The following example of eMembrane development gives an indication of the broad and 

varied possibilities for developing customized membranes and material surfaces, and 

draws heavily from company provided literature. eMembrane’s technology involves the 

nano-grafting of polymer chains containing selective binding functionalities. This 

technology can impart new and multiple polymeric material on existing materials and 

membranes. At the heart of the technology is the technique of electron-beam induced 

polymer grafting. Figure 10 provides a graphical representation of the technique showing 

the attachment of polymeric material. 

Figure 10. Electron-beam induced polymer grafting 

The polymer chains, or filaments, typically range from 10 nm to 300 μm long. The 

smallest filaments would catch ions and thus collect toxic metals from water. Larger 

filaments could hold gas or protein molecules, while the largest could capture whole cells 

or viruses in a bio-weapon defense system. There are as many as 10 trillion filaments on 

a square centimeter of substrate, spacing the filaments about 4 nm apart. 
54 

An electron beam irradiates a base membrane that can be made from any polymeric 

material. Other radiation sources, such as gamma rays, can also be used for similar 

radiation induced polymer grafting (Ramakrishna et al. 2005). The electron beam 

irradiation generates active species, or radicals, on the surface of the polymer. The active 

species are the sites at which other long polymer chains or brushes can be attached. The 

polymer brushes may contain the binding functionalities at the time of attachment, or 

they may be chemically functionalized after attachment has occurred. Electron beam 

irradiation is seen as an advantageous method of surface modification since it can occur 

after the basic polymer has been fabricated and does not affect the shape; by varying the 

electron beam energy and other process characteristics, the depth and degree of 

functionalization can be controlled. 

eMembrane’s electron-beam technology permits a density of polymer brush attachment 

that is extraordinary—up to 10 trillion polymer brushes per square centimeter can be 

attached giving a surface spacing of about 4 nm between each brush, a density far 

exceeding any other technique. The brushes can range from 10 to 300 nm long and can 

contain a variety of functionalities, allowing the production of highly tailored separation 

material. For example, a microporous membrane with grafted functionalized polymer 

brushes not only performs microfiltration (by molecular size cutoff), but the functional 

groups on its brushes can also simultaneously capture and remove toxic metal ions, 

soluble proteins, viruses, or cells from the filtrate. In effect, it has become an affinity 

membrane (Ofsthun et al. 1999, Zou et al. 2001, Nasef 2004, Klein 1991). Materials in a 

variety of shapes (e.g., film, hollow fiber, non-woven cloth, etc.) are grafted with 

polymer brushes that extend off the surface of the starting material. Figure 11 provides a 

graphical representation of the functionalized polymer surface with a variety of brushes 

attached to facilitate a number of separations. 

Figure 11. eMembrane-functionalized surface 
55 

Environmentally-related applications currently under investigation by eMembrane, Inc. 

include: 

Ion

• Removal, collection of heavy metal ions from fluids, 

• Ultra-pure water production 

• Immobilized metal affinity membrane 

Gas

• Removal of odors or toxic gases via neutralization 

Biological

• Tools for proteomics 

• Display of multilayer of various proteins for protein-protein interaction studies 

• Immobilized enzymes for proteomics, biosensors, and bioreactors 

• Large-scale biologics purification 

Cell

• Immobilized cells for proteomics studies 

• Removal of bacteria 

• Bioreactors, artificial organs 

Radiation cross-linking of naturally occurring polymers, such as polysaccharides, is being 

investigated for the production of biodegradable hydrogel/nanogel. This new 

nanomaterial consists of individual macromolecules that are internally cross-linked by 

irradiation ionizing radiation. 

Specifically modified nanogels are being studied for wastewater filtration. Gels 

containing acid groups have to bind ions, including uranium and nickel, for use in the 

removal of metals from aqueous media. These gels can be formulated and customized to 

remove most contaminants found in water. 

No fate and transport studies have been conducted, nor are anticipated, since this is a 

process unit rather than a material. Because the technology is in the development state, no 

operational or maintenance parameters have been determined, and no information on 

impacts, hazards, efficacy, limitations, and waste management approaches is available. 

One of the greatest, unknown concerns is what could happen if the fibers dislodge from 

the surface and enter the drinking water supply. 

 

2.4.6 References 

ASTM International. 2007. Standard Terminology Used for Microfiltration, 

Ultrafiltration, Nanofiltration and Reverse Osmosis Membrane Processes. Website. 

Accessed October 2007. 

http://www.astm.org/cgibin/SoftCart.exe/DATABASE.CART/REDLINE_PAGES/D616

1.htm?E+mystore. 
56 

Atkinson, S. 2002. Nanofiltration concentrates coloured wastewater and produces potable 

water. Membrane Technology. 2002(7): 11-12. 

Costa, A.R. and M.N. de Pinho. 2006. Comparison of the performance of ultrafiltration 

and nanofiltration in surface water treatment. Desalination. 199(1-3): 73-75. 

Gibson, R.R., B.F. Smith, G.D. Jarvinen, T.W. Robinson, R.E. Barrans, K.V. Wilson. 

1994. The Use of Water-Soluble Chelating Polymers as an Analytical Method for the 

Separation of Actinides in Aqueous Systems. Presentation at the Eighteenth Annual 

Actinide Separations Conference, Durango, CO, May 23-26, 1994. 

Jarvinen, G.D., R.E. Barrans, N.C. Jr., Schroder, K.L. Wade, M.M. Jones, B.F. Smith, 

J.L. Mills, G. Howard, H. Freiser, S. Muralidharan. 1995. Selective Extraction of 

Tetravalent Actinides from Lanthanides with Dithiophosphonic Acids and 

Tributylphosphate. In Separations of Elements. K.L. Nash and G.R. Choppin, eds. 

Plenum Press, New York, 43-62. 

Kawano, K., K. Hamaguchi, S. Masuda, T. Tomida. 2002. Binding Properties of a WaterSoluble Chelating Polymer with Divalent Metal Ions Measured by Ultrafiltration. Poly( -

acethylaminoacrylic acid). Industrial and Engineering Chemical Research. 41(20): 5079-

5084. 

Ki, C.S., E.H. Gang, I.C Um, Y.H. Park. 2007. Nanofibrous membrane of wool 

keratose/silk fibroin blend for heavy metal ion adsorption. Journal of Membrane Science. 

302(1-2): 20-26. 

Klein, E. 1991. Affinity Membranes: Their Chemistry and Performance in Adsorptive 

Separation Processes. Wiley-Interscience, Hoboken, NJ.

Lee, H.K., E.H. Jeong, C.K. Baek, J.H. Youk. 2005. One-step preparation of ultrafine 

poly(acrylonitrile) fibers containing silver nanoparticles. Materials Letters. 59(23):2977-

2980. 

Moreno-Villoslada I. and B.L. Rivas. 2002. Metal ion enrichment of a water-soluble 

chelating polymer studied by ultrafiltration. Journal of Membrane Science. 208(1-2): 69-

73. 

Nasef, M.M. 2004. Application of Electron Beam for Preparation of Membranes. Nippon 

Genshiryoku Kenkyujo JAERI, Conf Journal. 37-54. 

Ofsthun, N. J., P.J. Soltys, G.A. Kunas. 1999. Affinity membrane system and method of 

using same. U.S. Patent No. 5,871,649. 

Ramakrishna, S. W.-E. Teo, T.-C. Lim (Eds). 2005. Introduction to Electrospinning and 

Nanofibers. World Scientific Publishing Company, Singapore. 
57 

Ramakrishna, S., K. Fujihara, W.-E. Teo, T. Yong, Z. Ma, R. Ramaseshan. 2006. 

Electrospun nanofibers: solving global issues. Materials Today. 9(3): 40-50. 

Rautenbach R. and A. Groeschl. 1990. Separation Potential of Nanofiltration Membranes. 

Desalination. 77(1-3): 73-84. 

 

Rivas, B.L., E.D. Pereira, I. Moreno-Villoslada. 2003. Water-soluble polymer–metal ion 

interactions. Progress in Polymer Science. 28(2): 173-208. 

Rivas, B.L., S.A. Pooley, E.D. Pereira, A. Maureira. 2006. Water-Soluble 

Polyelectrolytes with Metal Ion Removal Ability by Using the Liquid Phase Based 

Retention Technique. World Polymer Congress - MACRO 2006. 245-246(1): 116-122. 

Sang, Y., F. Li, Q. Gu, C. Liang, J. Chen. 2008. Heavy metal contaminated groundwater 

treatment by a novel nanofiber membrane. Desalination. 223:349-360. 

Smith B.F. 1993. Actinide separations for advanced processing of nuclear waste: Annual 

Report 1993. Report LA-UR-93-4017, Los Alamos National Laboratory. 

Smith, B.F., T.W. Robinson, J.W. Gohdes. 1995. Water-Soluble Polymers and 

Composition Thereof. U.S. Patent DOE No. S-78, 350. 

Tomida T., T. Inoue, K. Tsuchiya, S. Masuda. 1994. Concentration and/or removal of 

metal ions using a water-soluble chelating polymer and a microporous hollow fiber 

membrane. Industrial and Engineering Chemistry Research. 33:904-906. 

Van der Bruggen B. and C. Vandecasteele. 2003. Removal of pollutants from surface 

water and groundwater by nanofiltration: overview of possible applications in the 

drinking water industry. Environmental Pollution. 122(3): 435-445.

Zou, H., Q. Lou, D. Zhou. 2001. Affinity membrane chromatography for the analysis and 

purification of proteins. Journal of Biochemical and Biophysical Methods. 49(1-3):199-

240. 
58 

2.5 Zeolites 

2.5.1 Introduction 

Zeolites are a well-established technology used in a range of processes and industries. 

Zeolites are not new materials—they have been investigated for over two and a half 

centuries, with stilbite and natrolite both being identified in the 1750s. Industrial 

applications include catalysis in the petroleum industry (Venuto and Dekker 1979, Chen 

et al. 1994), various uses in agriculture (St. Cloud 2007, BRZ Zeolite 2007, Zeolite 

Australia 2007), horticulture (ZeoPro 2007), gas separations (Yang 1994, Kerry 2007, 

Kanellopoulos 2000), domestic water treatment (McKetta 1999, Kawamura 2000, Faust 

1998); and nuclear waste processing (Auerback et al. 2003, Choppin and Khankhasayev 

1999). The value of zeolite catalysis to petroleum cracking is well in excess of $200 

billion (MassNanoTech 2007). About 50 naturally occurring zeolites have been 

identified; over 150 synthetic zeolites have been prepared and characterized; and further 

thousands of combinations of framework and composition are available (MassNanoTech 

2007, Baerlocher and McCusker 1996). Zeolites have long been used in the nuclear 

industry (Auerback et al. 2003, Choppin and Khankhasayev 1999) owing to their 

properties as ion exchangers. The planned siting of the United States’ first deep geologic 

radioactive waste repository at Yucca Mountain in Nevada, where design philosophy 

called for both engineered and natural barriers (Ahn et al. 1981) to inhibit the transport of 

any potentially leaking radionuclides, was influenced considerably by the local 

abundance of the natural zeolites mordenite and clinoptilolite, both of which have large 

cationic exchange capacities. 

2.5.2 Description 

Zeolites are crystalline aluminosilicates, compositionally similar to clay minerals, but 

differing in their well-defined three-dimensional nano- and micro-porous structure. 

Aluminum, silicon, and oxygen are arranged in a regular structure of [SiO4]

-

 and [AlO4]

- 

tetrahedral units that form a framework with small pores (also called tunnels, channels, or 

cavities) of about 0.1-2 nm diameter running through the material. Figure 12 shows a 

representation of a typical zeolite framework. It should be clearly noted that this is just 

one of a large and growing number of types of zeolite framework. In 1970, the Atlas of 

Zeolite Framework Types (Baerlocher and McCusker 1996) listed 27 known frameworks, 

but by 2003, the number had grown to 145. The variety of size and shape available for 

the pore structure is the source of zeolites’ catalytic activity that is so important to the 

petrochemical industry. 

A second consequence of the framework being built from negatively charged units is that 

it possesses a net negative charge that must be balanced by the presence of positively 

charged cations. Most naturally occurring zeolites have the environmentally predominant 

sodium ion as a loosely bound counter ion. These can be readily displaced by other ions 

for which a particular framework has a much greater affinity, thus giving zeolites 

significant ion exchange properties. 
59 

Figure 12. A typical zeolite structure 

It should be noted that the ion exchange and the pore size properties of zeolites are 

partially linked. When the zeolite is in the sodium form (i.e., it has positively charged 

sodium ions balancing the net negative charge on the aluminosilicate framework), the 

sodium ions are associated with the tetrahedral aluminum or silicon atoms at the entrance 

to the pores and, because of their finite size, they effectively reduce the diameter of the 

pore opening slightly. If the sodium ions are replaced by potassium ions, which are larger 

than the sodium ions, then the opening of the pore is effectively reduced even further. 

This behavior permits a degree of control over the size of material that can enter the 

pores. 

Zeolites are usually aluminosilicates, but other tetrahedral atoms such as phosphorus, 

gallium, germanium, boron, and beryllium can exist in the framework as well. 

 

2.5.3 Potential Applications 

General Applications. Zeolites have a wide range of commercial uses (InterSun 2007), 

including: 

Aquaculture

• Ammonia filtration in fish hatcheries 

• Biofilter media 

Agriculture

• Odor control 

• Confined animal environmental control 

• Livestock feed additives 
60 

Horticulture

• Nurseries, greenhouses 

• Floriculture 

• Vegetables/herbs 

• Foliage 

• Tree and shrub transplanting 

• Turf grass soil amendment 

• Reclamation, revegetation, and landscaping 

• Silviculture (forestry, tree plantations) 

• Medium for hydroponic growing 

Household Products

• Household odor control 

• Pet odor control 

Industrial Products

• Absorbents for oil and spills 

• Gas separations 

Environmental Applications. Although environmental applications of zeolites are small 

compared with applications of their catalytic properties, considerable research and some 

implementations have taken place including: 

Radioactive Waste

• Site remediation/decontamination 

Water Treatment

• Water filtration 

• Heavy metal removal 

• Swimming pools 

Wastewater Treatment

• Ammonia removal in municipal sludge/wastewater 

• Heavy metal removal 

• Septic leach fields 

Pasini (Pasini 1996) has described the state-of-the-art technology with regard to the use 

of natural zeolites in the protection of the environment. He focuses on the possible cation 

exchange procedures and principles that can be operated at an industrial level; the 

removal of NH4

+ from municipal and industrial wastewater; the possibilities for use of 

natural zeolites for removal of heavy metals from water after laboratory experiments; and 

how chemical and structural features make zeolites a powerful tool for the 

decontamination of waters containing radionuclides. The compendium by Misaelides et 

al. (1999) dealt with general environmental applications and contained much information 

on the use of zeolites as radionuclide sorbents (Macasek 1999, Bish 1999, Rajec et al. 

1999, Colella 1999), including consideration of the sorption and leaching properties of 

the composites and complexes of natural microporous materials; investigation of natural 

zeolites and nuclear waste management in the case of Yucca Mountain, Nevada; the 

sorption of heavy metals and radionuclides on zeolites and clays; and environmental 
61 

applications of natural zeolitic materials based on their ion exchange properties. As an 

example of the depth to which these studies can go, Komarneni (Komarneni 1985) 

investigated the use of one zeolite, phillipsite, in cesium decontamination and 

immobilization, citing: 

“The use of zeolites such as clinoptilolite in nuclear waste decontamination is a 

common practice (IAEA 1972). Zeolites and zeolitic tufts have also been used to 

decontaminate low and intermediate-level liquid nuclear wastes (Mercer and 

Ames 1978) and to separate 37Cs from high-level radioactive defense wastes at 

Hanford, Washington (Nelson and Mercer 1963, Brandt 1970, Buckingham 

1970). Zeolitic ion ex-changers, such as Ionsiv IE-95 (USNRC 1980) which 

consists of a mixture of natural chabazite and erionite from Bowie, Arizona and 

Ionsiv IE-96 (which consists of chabazite) + Linde A-51 (Hofstetter and Hitz 

1983) are currently used to clean up accident wastewater at the Three Mile 

Island-Unit II reactor, Middletown, Pennsylvania.” 

Radionuclide Applications. Zeolites are one of the few nanotechnologies that have been 

investigated for environmental remediation purposes. Because of their ion exchange 

properties, and the fact that they are a seemingly benign natural product that can bring 

certain improvements (such as increasing the soil cation-exchange capacity and soil 

moisture, improving hydraulic conductivity, increasing yields in acidified soils, and 

reducing plant uptake of metal contaminants) to soil properties (Allen and Ming 1995), 

zeolites have been examined for their ability to remediate heavy metals in soil (Weber et 

al. 1984). Based on this work, Campbell and Davies (Campbell and Davies 1997) 

performed an experimental investigation of plant uptake of cesium from soils amended 

with clinoptilolite and calcium carbonate. 

The origin of this work was the observation that radioactive cesium (137Cs) from the 

Chernobyl accident of 1986 has unexpectedly remained in a bioavailable form in upland, 

sheep-grazing soils of Great Britain. As a potential remedial measure, the zeolite 

clinoptilolite was tested in a greenhouse pot experiment for its effectiveness in selectively 

taking up cesium from two British soils: a lowland loam and an upland peat. Rye-grass 

grown on 10% clinoptilolite-treated soils resulted in grass leaf tissue cesium 

concentrations below 30 mg Cs kg-1 grass in all cases. Where no clinoptilolite had been 

added, cesium in grass leaf-tissue reached 1,860 mg kg-1 in rye grown on peat and 150 

mg kg-1 in rye grown on loam. In contrast, the addition of calcium carbonate to the Cstreated, clinoptilolite-free peat soil enhanced the grass concentration of Cs by 

approximately five times, but this effect was not observed with the concentration of Cs in 

grass grown from loam soils with the same treatments. 

However, despite this apparent beneficial result of adding the zeolite, adverse side effects 

were observed. Since the zeolite is in the sodium form, sodium ions are released and the 

risk of sodium toxicity to plants increases as cation exchange proceeds. Further, since 

clinoptilolite binds heavy metals in general, essential heavy metals (such as zinc) would 

be markedly decreased by the application of zeolite, which in turn could result in 

deficiency problems in animals. It was also noted that since grazing animals consume a 
62 

considerable amount of soil in their diet, the consumption of radionuclide-laden zeolites 

could itself bring risks. 

In general, it has been noted that the main research behind the use of natural zeolites as a 

remediation tool for contaminated soil has been conducted largely through laboratory and 

greenhouse trials. There is very little evidence in the literature to support the long-term 

use of natural zeolites in real remediation projects (Stead et al. 2000). It was also noted 

that the future potential of using zeolites has not been fully appreciated, and that there is 

an urgent need to undertake field trials and evaluate the in-situ efficiency for these 

remediation purposes. 

Since zeolites are natural materials and are mainly used in industrial processes, little 

research is focused on their fate and transport, though an extensive volume of work exists 

on their geological origin and behavior. Extensive data exists on operation and 

maintenance parameters. As would be expected, specific details are highly dependent on 

waste streams involved. Three references (IAEA 1967, IAEA 1984, IAEA 2002) 

discussed below provide an excellent overview of the issues involved. 

2.5.4 Impacts, Hazards, Efficacy, and Limitations 

Zeolites are a bulk commodity. World production is on the order of 4 million tons per 

year, with China producing and using about 2.5 million tons (primarily as a low-grade 

additive to pozzolan cement); U.S. consumption is about 0.5 million tons. The primary 

industrial use is as a petrochemical catalyst and the second largest use is as a detergent 

builder. Thus, the use of zeolites in radionuclide remediation would be expected to have 

little impact. Most zeolites, particularly those with current widespread uses, are regarded 

as a safe material; they are currently being marketed as a health food and references to 

their medicinal use date back thousands of years. Zeolites are also used as a feed additive 

for cattle, pigs, chicken, and fish. It should be noted, however, that one zeolite, erionite, 

is regarded as a carcinogen due to its fibrous nature and high iron content. 

Regarding efficacy, though zeolites have had limited uses in environmental remediation 

outside of their use in the nuclear industry as an ion exchanger for liquid radioactive 

waste management, they are seen as having significant potential. Even the drawbacks 

mentioned in the work of Campbell and Davies (Campbell and Davies 1997) (discussed 

in Section 2.5.3) should be surmountable. To eliminate the sodium toxicity risk to soil, 

the zeolite could be preconditioned into the ammonium form, which would likely lead to 

plant growth improvements. Overcoming the concern of nutritionally important soil 

nutrients binding together would require that the zeolite used (possibly synthetic) would 

be designed to have a very high specificity for the target radionuclide and little else. 

Alternatively, soil quality could easily be monitored and appropriate amendments made. 

 

2.5.5 Management of Zeolite Wastes

Ion exchange in general is one of the most well-developed, common, and effective 

treatment methods for liquid radioactive waste, and is widely used in the nuclear 

industry. Zeolites are a large component of the inorganic ion exchangers used and an 
63 

extensive amount of literature exists on various aspects of their treatment and disposal. 

Among the best overviews of this technology base are the series of technical reports 

issued by the International Atomic Energy Agency (IAEA) in 1967, 1984 and 2002 

(IAEA 1967, IAEA 1984, IAEA 2002). The information below draws largely from the 

most recent of these reports (IAEA 2002). 

Prior to treatment for disposal, two pre-treatments—dewatering and size reduction—may 

be needed. Dewatering is generally accomplished by pressure, vacuum filtration, or 

centrifugation. If drying is needed, hot air is usually used as the drying medium with a 

shallow bed of spent materials. Types of drying units include fluidized bed dryers, 

vertical thin film dryers, and cone dryers. 

Since inorganic ion exchange materials (such as zeolites) are generally resistant to 

degradation by radiation or biological actions, they are treated by the use of direct 

immobilization, or by high temperature processes (such as vitrification). The 

immobilization matrices currently used include vitrification, cement, bitumen 

encapsulation, polymer encapsulation, and disposal in high-integrity containers.

Vitrification has been widely evaluated for the immobilization of highly-active waste, 

such as waste from the reprocessing of spent nuclear fuel, and has been evaluated for the 

treatment of ion exchange resins (Jantzen et al. 1995, Cicero-Herman et al. 1998). The 

excellent leach resistance property of the resulting glass waste form is the principal 

advantage of vitrification. Vitrification processes are capital-intensive, and the melters 

have a relatively short operational life (approximately 5 years). Vitrification processes 

operate at temperatures ranging from 1100°C to 3000°C, depending on the waste 

composition and glass forming additives used. 

Cement immobilizing radioactive waste has been used in the nuclear industry and at 

nuclear research centers for more than 40 years. Detailed descriptions of the process can 

be found in references from the IAEA in 1993 and the Los Alamos National Laboratory 

in 1997. Cement has many characteristics in its favor: it is readily available and widely 

used in civil engineering, the raw material is inexpensive, and the processing equipment 

can be based on conventional technology. The resulting waste forms are strong; 

noncombustible and radiation resistant, have a high density (providing radiation 

shielding), have a reasonable chemical stability, and have a moderate resistance to the 

release of radionuclides. The high pH conditions typical for cement results in a low 

solubility for many radionuclides by the formation of hydrolyzed species, carbonates, 

etc., which provides a good resistance to leaching. The main disadvantage of the 

cementation of spent ion exchange materials is that the final waste volume is high 

compared with the initial volume, owing to the low waste loadings that are achievable. 

The loadings can be increased by a pretreatment (such as grinding) of the spent ion 

exchange materials before cementation, which improves the quality of the final cemented 

products. 

Bitumen is a generic term used to cover a wide range of high molecular weight 

Hydrocarbons. Bitumen encapsulation is currently not used in the United States for 
64 

disposal, although several bitumen varieties are commercially available overseas for the 

immobilization of radioactive waste, including spent ion exchange resins. The main 

characteristics that make bitumen suitable as a matrix material are: 

• Its insolubility in water; 

• Its high resistance to the diffusion of water; 

• Its chemical inertness; 

• Its plasticity and good rheological properties; 

• Its good aging characteristics; 

• Its high incorporation capacity, which leads to high volume reduction factors; and 

• Its instant availability at a reasonable cost. 

However, since it is an organic material, bitumen has the following disadvantages: 

• It decreases in viscosity as a function of temperature, leading to a softening of the 

matrix, which melts at temperatures of about 70°C; 

• It is combustible, although not easily flammable (the flash point and flammability 

temperatures are higher than 290°C to 350°C, depending on the type of bitumen); 

• It has a lower stability against radiation than cement, especially under the higher 

radiation fields often associated with spent ion exchange media; and 

• It reacts with oxidizing materials such as sodium nitrate. 

The immobilization of spent ion exchange resins in polymers is practiced at many 

installations worldwide. Different types of polymers are used and further studies to 

improve cost effectiveness, process simplicity, and product quality are being carried out 

in many countries. Among the many polymers used are epoxy resins, polyesters, 

polyethylene, polystyrene and copolymers, urea formaldehyde, polyurethane, phenolformaldehyde, and polystyrene. 

 

2.5.6 Summary of Environmental Potential 

Zeolites are a well-established technology with a variety of industrial uses ranging from 

construction materials and detergent builders, to catalysts and separation agents. They are 

one of the oldest separation technologies for the removal of radioactive components from 

aqueous waste streams. The flexible tectonic structure and ability to be chemically 

“tailored” to specific target species continues to stimulate their development. In addition 

to their use as an “end-of-pipe” treatment for aqueous streams, zeolites are one of the few 

materials offering the possibility of being an inexpensive amendment to soils 

contaminated with radioactive species, since extremely high species selectivity and 

binding strength can be designed into the material. Continued investigation of zeolites in 

general is expected due to their catalytic properties; research in this area should support 

further developments, potentially leading to environmental applications. 
65 

2.5.7 References 

Ahn, T.M., R. Dayal, R.J. Wilke. 1981. Evaluation of backfill as a barrier to radionuclide 

migration in a high level waste repository. Technical Report BNL-NUREG-30107; 

CONF-810499-2, Brookhaven National Laboratory. Website. Accessed November 2007. 

http://www.osti.gov/energycitations/product.biblio.jsp?osti_id=5158859. 

Allen, E. R. and D. W. Ming. 1995. Recent Progress in the Use of Natural Zeolites in 

Agronomy and Horticulture. Natural Zeolites '93, Occurrence, Properties, Use; D. W. 

Ming and F. A. Mumpton, (Eds.); International Committee on Natural Zeolites. 

Brockport, New York. 

Auerback, S.M., K.M. Carrado, P.K. Dutta. 2003. Handbook of Zeolite Science and 

Technology. Marcel Dekker, Inc., New York. 

Baerlocher Ch. and L.B. McCusker. 1996. Database of Zeolite Structures. Website. 

Accessed November 2007. http://www.iza-structure.org/databases/. 

Bish, D.L. 1999. Natural Zeolites and Nuclear Waste Management; The Case of Yucca 

Mountain, Nevada, USA. In Natural Microporous Materials in Environmental 

Applications. P.Misaelides, F. Macasek, T.J. Pinnavaia, and C. Colella (Eds.). Kluwer 

Academic Publishers, The Netherlands. 

Brandt, H.L. 1970. B-plant recovery of cesium from Purex supernatant. Report ARH1639. United States Atomic Energy Commission, Hanford, Washington. 

 

BRZ Zeolite. 2007. Website. Accessed October 2007. 

http://www.zeolite.ca/agriculture.htm

Buckingham, J. S. 1970. Laboratory evaluation of zeolite material for removing 

radioactive cesium from alkaline waste solutions. Report ARH-SA-49. United States 

Atomic Energy Commission, Hanford, Washington. 

Campbell, L.S., and B.E. Davies. 1997. Plant and Soil. 189(1):65-74. 

Chen, N.Y., T.F. Degnan, C.M. Smith. 1994. Molecular Transport and Reaction in 

Zeolites: Design and Application of Shape Selective Catalysis. Wiley, VCH, Hoboken, 

NJ. 

Choppin, G.R. and M.K. Khankhasayev. 1999. Chemical Separation Technologies and 

Related Methods of Nuclear Waste Management: Applications, Problems, and Research 

Needs (NATO Science Partnership Sub-Series: 2). Springer, New York. 

Cicero-Herman, C.A., P. Workman., K. Poole, D. Erich, J. Harden. 1998. Commercial 

Ion Exchange Resin Vitrification in Borosilicate Glass. Westinghouse Savannah River 

Co., Aiken, SC. 
66 

Colella, C. 1999. Environmental Applications of Natural Zeolitic Materials Based on 

Their Ion Exchange Properties. In Natural Microporous Materials in Environmental 

Applications. P.Misaelides, F. Macasek, T.J. Pinnavaia, and C. Colella (Eds.). Kluwer 

Academic Publishers, The Netherlands. 

Faust, S.D. 1998. Chemistry of Water Treatment. ISBN-10: 1575040115; ISBN-13: 978-

1575040110. 

Hofstetter, K. J. and Hitz, C. G. 1983. The use of the submerged demineralizer system. 

Separation Science Technology. 18:1747-1764. 

International Atomic Energy Agency (IAEA). 1967. Operation and Control of Ion 

Exchange Processes for Treatment of Radioactive Wastes, Technical Reports Series No. 

78. 

International Atomic Energy Agency (IAEA). 1972. Use of local minerals in the 

treatment of radioactive wastes: Technical Report Series 136. 

International Atomic Energy Agency (IAEA). 1984. Treatment of Spent Ion-exchange 

Resins for Storage and Disposal, Technical Reports Series No. 254. 

International Atomic Energy Agency (IAEA). 2002. Application of Ion Exchange 

Processes for the Treatment of Radioactive Waste and Management of Spent 

Ion Exchangers, Technical Reports Series No. 408. 

InterSun. 2007. Zeolite Applications. Website. Accessed October 2007. 

http://www.siberg.com/zeolite.htm. 

Jantzen, C.M., D.K. Peeler, C.A. Cicero. 1995. Vitrification of Ion-exchange (IEX) 

Resins: Advantages and Technical Challenges. Westinghouse Savannah River Co., 

Aiken, SC. 

Kanellopoulos, N.K. (ed.). 2000. Recent Advances in Gas Separation by Microporous 

Ceramic Membranes. Elsiever, New York. 

Kawamura, S. 2000. Integrated Design and Operation of Water Treatment Facilities.

Wiley, Hoboken, NJ. 

Kerry, F. G. 2007. Industrial Gas Handbook: Gas Separation and Purification. CRC 

Press, Boca Raton, FL. 

Komarneni, S. 1985. Philipsite In Cs Decontamination and Immobilization. Clays and 

Clay Minerals. 33(2):145-151. 
67 

Los Alamos National Laboratory. 1997. Cement Waste-form Development for Ionexchange Resins at the Rocky Flats Plant. Rep. LA-13226. 

Macasek, T.J. 1999. Sorption and Leaching Properties of the Composites and Complexes 

of Natural Microporous Materials. In Natural Microporous Materials in Environmental 

Applications. P. Misaelides, F. Macasek, T.J. Pinnavaia, and C. Colella (Eds.). Kluwer 

Academic Publishers, The Netherlands. 

MassNanoTech. 2007. University of Massachusetts Nanoscale Science and Engineering. 

Website. Accessed October 2007. 

http://www.umass.edu/massnanotech/faculty_auerbach.htm. 

McKetta, J.J. 1999. Encyclopedia of Chemical Processing and Design: Volume 67 -

Water and Wastewater Treatment: Protective Coating Systems to Zeolite, 1st Edition.

CRC Press, Boca Raton, FL. 

Mercer, B. W. and L.L. Ames. 1978. Zeolite ion exchange in radioactive and municipal 

wastewater treatment. In Natural Zeolites: Occurrence, Properties, Use. L. B. Sand and 

F. A. Mumpton (eds.). Pergamon Press, Elmsford, New York, 451-462. 

Misaelides, P., F. Macasek, T.J. Pinnavaia, C. Colella (Eds.). 1999. Natural Microporous 

Materials in Environmental Applications. Kluwer Academic Publishers, The Netherlands. 

Nelson, J. L. and Mercer, B. W. 1963. Ion exchange separation of cesium from alkaline 

waste supernatant solutions. United States Atomic Energy Commission, Hanford, 

Washington. 

Pasini, M. 1996. Natural zeolites as cation exchangers for environmental protection. 

Mineralium Deposita. 31(6):563-575. 

Rajec, P., F. Macasek, P.Misaelides. 1999. Sorption of Heavy Metals and Radionuclides 

on Zeolites and Clays. In Natural Microporous Materials in Environmental Applications.

P. Misaelides, F. Macasek, T.J. Pinnavaia, and C. Colella (Eds.). Kluwer Academic 

Publishers, The Netherlands. 

St. Cloud. 2007. Zeolite. Website. Accessed October, 2007. 

http://www.stcloudmining.com/agriculture.html. 

Stead, K., S.K. Ouki, N.Ward. 2000. Natural Zeolites—Remediation technology for the 

21st Century. Eurosoil 2000, British Society of Soil Science, University of Reading, 

September 4-6, 2000. 

United States Nuclear Regulatory Commission (USNRC). 1980. Draft Programmatic 

environment impact statement related to decontamination and disposal of radioactive 

wastes resulting from March 1979 accident. Three Mile Island Nuclear Station, Unit 2: 

U.S. Nuclear Regulatory Commission Report NUREG- 0683, Washington, DC. 
68 

Venuto, P.B. and M. Dekker. 1979. Fluid Catalytic Cracking with Zeolite Catalysts.

ISBN-10: 0824777824; ISBN-13: 978-0824777821. Washington, Report HW-76449, p.3. 

Weber, M. A., K. A. Barbarick, and D. G. Westfall. 1984. Application of clinoptilolite to 

soil amended with sewage sludge. Zeo-Agriculture: Use of Natural Zeolites in 

Agriculture and Aquaculture. W. F. Pond and F. A. Mumpton (Eds.) Westview Press, 

Boulder, CO. 

Yang, R.T. 1994. Gas Separation by Adsorption Processes. World Scientific Publishing 

Company, Imperial College Press, Singapore. 

Zeolite Australia PTY LTD. 2007. Website. Accessed October 2007. 

http://www.zeolite.com.au/products/agriculture.html. 

ZeoPro. 2007. Website. Accessed October 2007. http://www.zeoponix.com/zeolite.htm. 
69 

2.6 Other Nanoparticles 

Though iron nanoparticles presented in Section 2.2 are the most fully developed type of 

nanoparticle for environmental remediation, they are not the only type of nanoparticle 

that has been suggested for environmental remediation. Some additional possibilities 

include the use of TiO2 nanoparticles as photocatalysts for the destruction of organic 

pollutants (Rajh et al. 2003), the separation of ionic solutes using nanoparticlecrosslinked polymer hydrogels (Thomas et al. 2003), or the use of coated magnetic 

nanoparticles in high-gradient magnetic separations (Moeser et al. 2004). The subsections 

below present information on three possibilities: nanodiamonds, dendrimers, and 

Argonne Supergel. 

Nanodiamonds are the subject of much research due to their potential in electronic and 

bio-imaging applications, and because they can be prepared directly, simply, and in 

potentially large amounts. They are apparently biologically benign, and their ease of 

surface functionalization and magnetic properties make them a potential separation 

platform. 

Dendrimers are a new class of polymer with tailorable properties, both at the surface and 

in the interior of the particle. They have been of great interest in the area of separations, 

and are potential complements to separation processes involving nanofiltration or 

microfiltration. 

Argonne Supergel is presented as a nano-enabled technology developed specifically for 

radionuclide decontamination. These three examples (nanodiamonds, dendrimers, and 

Supergel) are presented to provide a sense of the range of possibilities that nanoparticles 

can offer for separation-based remediation. 

2.6.1 Nanodiamonds 

Nanodiamond is a term used for a group of diamond-related materials with nanoscale 

dimensions, including diamond films and diamond nanoparticles. These are prepared by a 

variety of methods, including high-pressure gas-phase nucleation and application of 

shock waves to graphite (Dolmatov 2001). Within this group of diamond materials lies a 

subgroup called detonation Nanodiamond (DND), or ultrananocrystalline diamond 

(UNCD). These materials were discovered in Russia in 1963, and produced by the 

detonation of oxygen deficient explosives, such as a 3-to-2 mixture of 2,4,6-

Trinitrotoluene (TNT) and Hexahydro-Trinitro-Triazine (RDX). Figure 13 shows a 

Transmission Electron Microscope (TEM) image of DNDs. 

DNDs were unknown in the West until recently, and have attracted much interest (Petrov 

et al. 2006, Gruen et al. 2005) because of their unusually uniform shape and size 

distribution and the fact that they can be produced in large quantities (Osawa 2003). 

Before DND was widely known, Western industry produced microdiamonds by applying 

an externally produced shockwave to heated graphite at high pressures. This produced a 

polycrystalline material with a wide size distribution and very few particles reaching 
70 

down to the 10-20 nm size range. In contrast, DND has a fairly tight size distribution in 

the 3-5 nm range, consisting of about 5,000 carbon atoms, and has a regular octahedral 

shape (Figure 14). 

Figure 13. TEM image of DND 

Figure 14. Model of nanodiamonds demonstrating their regular octahedral shape 

Nanodiamond production from a detonation produces a sooty product that is 

approximately 50% DND. To obtain the nanodiamonds from this mixture, two challenges 

must be overcome—the presence of graphitic impurities and the fact that the diamonds 

tend to aggregate into clusters with average sizes of 30 μm, 3 μm, and 100-200 nm. The 

aggregates can be broken up by a combination of ultrasound and high-speed zirconia 

bead milling. 
71 

Nanodiamonds possess interesting properties. Their surfaces have a tendency to change 

from the regular diamond structure to a fullerene (buckyball) structure (Figure 15), 

resulting in a material that appears to have a diamond within a fullerene cage and has 

some of the physical properties of the nanodiamond combined with the rich chemistry of 

the fullerene. 

Figure 15. Structure with nanodiamond center and fullerene-like surface 

The potential for surface chemical functionalization opens up a wide range of possible 

applications for derivatized material. Even without chemical functionalization, 

nanodiamonds have been suggested for a range of applications, including: 

• Lapping and polishing applications 

• All-rigid memory disk substrate 

• Polycarbonate and CR-39 eyeglass lenses 

• Miniature and precision ball bearings 

• Optical and laser optical components 

• Ceramics 

• Precious stones 

• Metallic mirrors and precision metal polishing 

• Ferrite surface preparation 

• Mechanical seal lapping 

• Superhard and soft nanoabrasives 

Other applications include: 

• Surface germination for following growth of diamond-like films 

• Ni-Diamond and Cr-Diamond electroplated hard coatings 

• Molecular sieves 

• Lubricant additive to engine oil 

• Dry lubricants for metal industry (drawing of W-, Mo-, V-, Rh-wires) 

• Reinforcing fillers for plastics and rubbers 

• Chromatographic carriers 
72 

A major area that is being investigated is the biomedical potential of nanodiamonds, 

including their roles as drug carriers, implant coatings, and medical nanorobots. 

Nanodiamonds are soluble in water, can be functionalized, and appear to be biologically 

benign. Cytotoxicity research findings from the University of Dayton indicate that 

nanodiamonds are biologically compatible materials across a range of sizes with regard to 

a variety of cell types, with or without surface modifications (Schrand et al. 2007). 

Nanodiamonds have also been suggested as sorbent materials (Dolmatov 2001, Gruen et 

al. 2005), giving rise to the possibility of environmental remediation applications. Their 

observed magnetic properties (Talapatra 2005) also open the possibility of their use in 

magnetic separations. The radiation stability of the carbon also opens up the possibility as 

a disposal waste form. 

2.6.2 Dendrimers 

A dendrimer is a highly and repetitively branched, three-dimensional polymer created by 

a sequence of iterative chemical reactions starting from a central core. Each iteration is 

known as a generation and has twice the complexity of the prior generation. The term 

comes from dendron (the Greek word for tree), with the analogy being the branch-like 

structure of the dendrimer. Dendrimers have been called the fourth major class of 

polymeric architecture (after linear, cross-linked, and branched polymers), but unlike 

other polymers where atom-by-atom control is not feasible and polydispersity (and the 

variability it brings) is an inherent characteristic, dendrimers are characterized by 

monodispersity (i.e., all dendrimer molecules are of a uniform and controllable size) and 

well-defined properties. Figure 16 provides a graphical representation of a generalized 

dendrimer structure. 

Figure 16. A generalized dendrimer structure 
73 

Figure 16 allows some of the special chemical properties of dendrimers to be explained. 

Starting at the core (G0) and moving through branching points G1 and G2, it can be seen 

that as the dendrimer branches out in a predictable manner, large voids can exist within 

the dendrimer internal structure. Both the size and the physical nature (e.g., hydrophobic 

or hydrophilic characteristics) of these voids can be controlled during synthesis by 

judicious selection of both the length and composition of the branch backbone. These 

voids can be used to store material (metals, organic and inorganic molecules, and even 

other nanoparticles), and together with the fact that dendrimers can easily move across 

biological membranes, the controllable nature of the voids has led to suggested 

applications of dendrimers as carriers of genetic material into cells (Kukowska-Latallo et 

al. 1996), drug delivery agents (Lim and Simanek 2005), and diagnostic imaging agents 

(Tomalia 2003). The voids can also be used to hold material undergoing reactions and 

has led to investigations of dendrimers as nanoreactors (Chung and Rhee 2003). 

A second feature that is illustrated in Figure 16 is the surface formed by the terminal 

groups. As the number of generations of the dendrimer increases, the total external 

surface area rises dramatically. If the terminal groups are designed to be binding moieties 

for other species, then it is apparent that a dendrimer, compared to say a macroscopic 

bead of ion exchange resin (which will have a much smaller surface area than an 

equivalent amount of dendrimer), can potentially bind up a large amount of target 

material. It is this aspect of dendrimers that is of prime concern for environmental 

applications. Current expertise in dendrimer synthesis also allows for more than one type 

of terminal group to be attached to the dendrimer, thus offering the possibility of 

multifunctional molecules. Terminal groups can be attached to modify solubility, modify 

binding capacity and specificity, and to allow further reaction with or attachment to other 

surfaces or nanoparticles. It has been suggested that amphipathic dendrimers could be 

synthesized with one half of the molecule (or one hemisphere) covered in hydrophobic 

groups, and the other half containing hydrophilic groups. 

Due to the degree of structural control that dendrimers make possible, and the fact that 

their highly customizable properties should make them building blocks for other 

nanomaterials, they have been the subject of much research, with the number of academic 

publications approaching ten thousand. Commercial development has been slower than 

once anticipated because of their high cost (on the order of $10 per milligram) and the 

complexity of scaling-up production. Though these factors are themselves subject of 

much research, dendrimers already have a market or near-market presence: 

• Dade Behring, one of the world’s largest medical diagnostic firms, is developing a 

dendrimer-based, rapidly responding tool for detecting heart attacks and cardiac 

damage. 

• The U.S. Army Research Laboratory is developing a dendrimer-based anthrax 

detection agent. 

• Starpharma is developing the world’s first dendrimer-based drug, Vivagel, to fight 

sexually transmitted infections. It has been awarded $20 million by the National 

Institutes of Health (NIH) to develop its HIV indication; given further awards to 
74 

develop its genital herpes indication; and was granted Fast Track status by the 

U.S. FDA in 2006 as a product for preventing HIV infection. 

Dendrimers are currently under investigation as metal sequestering agents for waste 

remediation technologies (Cohen et al. 2001), and for the removal of uranium from 

aqueous streams (Diallo 2007). In the latter work, dendrimers may be compared with 

chelating agents, which are widely used in uranium separation processes, such as solvent 

extraction or ion exchange resins. Ion exchange resins with amino groups typically bind 

on the order of 100 mg of uranium per gram of resin, while the work with 

poly(amidoamine) and poly(propyleneimime) dendrimers, which contain nitrogen and 

oxygen donors, can bind up to 2500 mg of uranium per gram of dendrimer without 

reaching saturation in either acid or basic solutions. Further, the binding kinetics of the 

dendrimers to uranium is very fast and reaches equilibrium in less than 20 minutes. Rapid 

equilibration, high loading capacity, and selectivity mean that such dendrimers could thus 

serve as high capacity and selective chelating agents for uranium. The dendrimeruranium complexes could be easily separated by ultrafiltration and then regenerated, thus 

avoiding the need to add further reagents and simplifying the overall process. 

2.6.3 Argonne Supergel 

Argonne National Laboratory (ANL) has developed a system, called the “Supergel” 

technique, to safely capture and dispose of radioactive elements in porous structures 

outdoors (such as buildings and monuments), using a spray-on, super-absorbent gel and 

engineered nanoparticles (ANL 2006). Porous structures are notoriously hard to clean. In 

decommissioning and decontamination operations, it is common practice to demolish 

contaminated structures or completely remove a significant surface layer rather than 

attempt to remove radioactivity. ANL’s Supergel technique preserves surfaces, which 

means that monuments or buildings would not have to be defaced to remove radiation. 

The Supergel was developed with funding from the Department of Homeland Security to 

help fill a technology gap in preparedness for a terrorist attack with a “dirty bomb” or 

other radioactive dispersal device, but it could also be used in more general 

decontamination situations. 

The Supergel technique uses commercially available equipment in a simple procedure. 

First, a wetting agent and a super-absorbent gel are sprayed onto the contaminated 

surface. The polymer gel used to absorb the radioactivity is similar to the absorbent 

material found in disposable diapers. When exposed to water, the polymers form 

something similar to a structural scaffold that allows the gel to absorb a large amount of 

liquid. When sprayed on concrete, the wetting agent causes the bound radioactivity to resuspend in the concrete pores and the superabsorbent polymer gel then draws the liquid 

out, along with the resuspended radioactivity. Inside the gel, the radioactive material 

becomes fixed by engineered nanoparticles that also reside in the gel. After a period of 

standing, the gel is vacuumed and recycled, leaving behind a relatively small amount of 

radioactive waste for disposal. 

 

 
75 

2.6.4 Summary of Environmental Potential 

These three technologies—nanodiamonds, dendrimers, and Supergel—demonstrate the 

broad potential of nanoparticles. Nanodiamonds, though relatively new, offer a wide 

range of potential applications and can be produced in bulk at reasonable prices. 

Dendrimers are a new class of polymer architecture that has caused much excitement due 

to the potential of engineering properties at the molecular level into materials of uniform 

and controllable size. The Argonne Supergel shows the ease with which nanoparticles 

can be incorporated into other applications to address highly specific technology needs. 

2.6.5 References 

Argonne National Laboratory (ANL). 2006. ‘Supergel’ Systems Cleans Radioactively 

Contaminated Structures. Website. Accessed October 2007. 

http://www.anl.gov/National_Security/docs/factsheet_Supergel.pdf. 

Chung, Y.-M., and H.-K. Rhee. 2003. Pt-Pd Bimetallic Nanoparticles Encapsulated in 

Dendrimer Nanoreactor. Catalysis Letters. 85(3-4): 159-164. 

Cohen, S.M., S. Petoud, K.N. Raymond. 2001. Synthesis and Metal Binding Properties of 

Salicylate-, Catecholate-, and Hydroxypyridinonate-Functionalized Dendrimers. 

Chemistry. 7(1): 272-279. 

Dolmatov, V.Y. 2001. Detonation synthesis ultradispersed diamonds: properties and 

applications. Russian Chemical Reviews. 70: 607. 

 

Diallo, M.S. 2007. Dendrimer Based Chelating Agents and Separation Systems for 

U(VI): Fundamental Investigations and Applications to In situ Leach Mining. 

Presentation at the Global Uranium Symposium, Corpus Christi, TX, May 2007. 

Gruen, D.M., A.O. Shenderova, A.Y. Vul (Eds.). 2005. Synthesis, Properties and 

Applications of Ultrananocrystalline Diamond: Proceedings of the NATO Advanced 

Research Workshop on Synthesis, Properties and Applications of Ultrananocrystalline 

Diamond. St. Petersburg, Russia, 7-10 June 2004. Springer, New York. 

Kukowska-Latallo, J.F., A.U. Bielinska, J. Johnson, R. Spindler, D.A. Tomalia, J.R. 

Baker, Jr. 1996. Efficient transfer of genetic material into mammalian cells using 

Starburst polyamidoamine dendrimers. National Academy of Science. 93(10): 4897–

4902. 

Lim, J. and E.E. Simanek. 2005. Toward the Next-Generation Drug Delivery Vehicle: 

Synthesis of a Dendrimer with Four Orthogonally Reactive Groups. Molecular 

Pharmaceutics. 2 (4), 273 -277. 
76 

Moeser, G.D., K.A. Roach, W.H. Green, T.A.Hatton, P.E. Laibinis. 2004. High-gradient 

magnetic separation of coated magnetic nanoparticles. A.I.Ch/E. Journal. 50 (11): 2835-

2848.

Osawa, Eiji. 2003. Detonation Nanodiamond-Potential Material For FED. American 

Physical Society, Annual APS March Meeting 2003, March 3-7, 2003. 

 

Petrov, I., P. Detkov, J. Walch and O. Shenderova. 2006. Polydispersed Detonation 

Nanodiamond and Approaches for its Fractioning. In Technical Proceedings of the 2006 

NSTI Nanotechnology Conference and Trade Show, Volume 1. NSTI, Cambridge, 

Massachusetts: 150-153. 

Rajh, T., O. V. Makarova, M. C. Thurnauer, and D. Cropek. 2003. Surface Modification 

of TiO2: a Route for Efficient Semiconductor Assisted Photocatalysis; Chapter 9 in 

Synthesis, Functionalization and Surface Treatment of Nanoparticles. M.-I. Baraton 

(Ed.), American Scientific Publishers, California: 147-171. 

Schrand, A.M., H. Huang, C. Carlson, J.J. Schlager, E.O. Sawa, S.M. Hussain, L. Dai. 

2007. Are Diamond Nanoparticles Cytotoxic? Journal of Physical Chemistry B. 111:2-7. 

Thomas, P., B. Cipriano and S. Srinivasa Raghavan. 2003. Separation of Ionic Solutes 

Using Nanoparticle-Crosslinked Polymer Hydrogels; Presentation at the American 

Physical Society March Meeting, Denver, CO, March 6. 

Tomalia, D. 2003. Dendrimers as multi-purpose nanodevices for oncology drug delivery 

and diagnostic imaging. Nanomedicine: Nanotechnology, Biology and Medicine. 2(4): 

309. 
77 

2.7 Uranium Reduction by Bacteria 

Bioreductive immobilization of uranium is a quasi nanotechnology. The precipitated 

uranium and other minerals are in the form of nano size particles, whereas the bacteria 

are about 1 μm. In this section, the process is described, equations are provided, and 

photographs presented showing the nanoscale uraninite particles. 

The large number of contaminated sites and volumes of contaminated groundwater and 

soil call for innovative and economically attractive remediation technologies. To date, 

pump-and-treat is the most widely used technology. Frequently, pump-and-treat has been 

ineffective in permanently lowering contaminant concentrations in groundwater (Travis 

and Doty 1990). A recent study by Quinton et al. (Quinton et al. 1997) showed that 

groundwater cleanup technologies (such as pump and treat, permeable reactive barriers 

with ZVI, and bio-barriers) are more expensive than in-situ bioremediation. 

Microorganisms can reduce uranium indirectly by producing hydrogen sulfide (H2S) or 

pure hydrogen (H2) in the course of other processes (abiotic reduction) or directly using 

enzymes (enzymatic reduction). The first microorganisms identified to enzymatically 

reduce U(VI) were the dissimilatory Fe(III)-reducing microorganisms, Geobacter 

metallireducens and Shewanella putrefaciens (Lovley et al. 1991). These microorganisms 

used uranium as an electron acceptor, H2 or acetate as an electron donor to support 

growth, and tolerated U(VI) concentrations as high as 8 mM. Several authors studied the 

enzymatic reduction of U(VI) by various pure or mixed cultures of microorganisms, 

including metal- and sulfate-reducing bacteria (a summary of previous work can be found 

in Abdelouas et al. 1999a). These authors reviewed the literature on microbial reduction 

of uranium and the significance of biogeochemical processes related to uranium mining, 

tailings, and groundwater remediation. In Figure 17, the key reductive and oxidative 

reactions are shown for this process; in Figure 18, a bacterium is shown surrounded by 

nanosize uraninite particles. 
78 

Figure 17. Reductive and oxidative reactions 

Figure 18. Microphotographs showing a bacterium surrounded with uraninite 

nanoparticles 

500 nm Uraninite 

Bacterium 

1/5 NO3

-

 + 6/5 H+ + e 1/10 N2 (g) + 3/5 H2O 

1/4 O2(g) + H+ + e 1/2 H2O

1/2 MnO2 +1/2 HCO3

-

 + 3/2H+ + e 1/2 MnCO3(s) + H2O 

FeOOH(s) + HCO3

-

 + 2 H+ + e FeCO3(s) + 2 H2O 

1/8 SO4

2- + 9/8 H+

 + e 1/8 HS- + 1/2 H2O 

Decreasing

redox intensity

1/5 C2H5OH + 1/4 H2O 1/6 CO2 + H+ + e 

• Oxidation of ethanol

1/2 UO2(CO3)2

2- + H+

 + e 1/2 UO2(s) + HCO3

- 
79 

The first demonstration of a feasible process for the in-situ immobilization of uranium as 

a bioremediation strategy was conducted by a team of scientists from the University of 

Massachusetts, PNNL, the University of Tennessee, and several other institutions 

(Anderson 2003). The team conducted a two-month field study and demonstrated that by 

adding acetate to the subsurface, they could stimulate the growth and proportion of 

Geobacter species within the subsurface microbial community. At the same time, the 

concentration of uranium in the ground water was greatly reduced. 

The observation of bacteria able to immobilize uranium is an area of active study, both 

from biochemical and nano-geological perspectives. Comparatively little is known about 

either the bacteria or the processes they use; even questions over the long-term stability 

of the immobilized uranium have yet to achieve a comprehensive answer. Recent 

research at Virginia Polytechnic Institute (Virginia Tech 2006) with Shewanella 

oneidensis MR-1 (one of the most common bacteria in the Earth) has shown that particle 

size is important, with smaller nanoparticles of the iron (III) oxide hematitie showing a 

lower rate of reduction than larger nanoparticles. Research on the same bacterium at 

PNNL (Marshall 2006) has demonstrated that much of Shewanella’s biochemistry of 

immobilization occurs outside the cell, producing uniform, 5-nm particles of uraninite 

trapped as strings of particles in a glue-like extracellular polymeric substance (Figure 19). 

Figure 19. Uraninite nanoparticles trapped in an extracellular polymeric substance 

exuded by Shewanella

A current five-year, $15-million U.S. Department of Energy (DOE) project led by Oak 

Ridge National Laboratory (ORNL) (Edwards 2007) is trying to provide a further 

understanding of the coupled microbiological and geochemical processes limiting 

radionuclide bioremediation, and through an examination of terminal-electron accepting 

processes involving geobacteraceae has shown that due to the stress imposed by low pH 

on microbial metabolism, the terminal-electron accepting processes of acidic subsurface 

sediment are inherently different from those of neutral pH environments and 
80 

neutralization will be necessary to achieve sufficient metabolic rates for radionuclide 

remediation. 

In addition to direct bacterial processes for the reduction of uranium, indirect processes 

may occur where bacteria or other microbes assist in the reduction processes by control 

of the chemical environment. The dissimilatory iron reducing bacteria mentioned above 

metabolically couple the oxidation of organic compounds with the reduction of Fe (III) 

generating energy and Fe(II) complexes, the latter of which in turn lead to the production 

of a range of Fe(II) minerals such as magnetite, siderite, vivianite, ferruginous smectite, 

and green rust. In fact, the oxidation/reduction behavior of uranium, together with the 

ability of micro-organisms to take advantage of such oxidation/reduction behavior, may 

well play a significant role in the formation of uranium ore deposits (Dexter-Dyer 1984). 

This behavior is being exploited in the concept of microbial mining of uranium, and may 

be of importance to remediation. An example is “green rust”, a class of iron (II)/iron (III) 

hydroxide compounds having a pyroaurite-type structure consisting of alternating 

positively charged hydroxide layers and hydrated anion layers. Green rusts are products 

of both abiotic and microbially induced corrosion of iron, and occur in both microbially 

mediated and abiotic reductive dissolution of ferric oxyhydroxides. Extended X-Ray 

Absorption Fine Structure (EXAFS) studies have shown that uranyl ion can be reduced to 

UO2 (U(IV)) by green rust (O’Loughlin 2003), with the uraninite forming nanoparticles 

on the green rust crystal surface (Figure 20). 

Figure 20. Uraninite nanoparticles on a green rust particle 

The DOE has funded a project through its Environmental Management Science Program 

(EMSP) to examine the processes underlying the potential use of dissimilatory metalreducing bacteria (DMRB) to create subsurface redox barriers for immobilizing uranium 
81 

and other redox-sensitive metal/radionuclide contaminants (Roden 2005). The results of 

these studies suggest that: 

• the efficiency of dissolved U(VI) scavenging may be influenced by the kinetics of 

enzymatic U(VI) reduction in systems with relative short fluid residence times; 

• association of U(VI) with diverse surface sites in natural soils and sediments has 

the potential to limit the rate and extent of microbial U(VI) reduction, and in turn 

modulate the effectiveness of in-situ U(VI) bioremediation; and 

• abiotic, ferrous iron (Fe(II))-driven U(VI) reduction is likely to be less efficient in 

natural soils and sediments than would be inferred from studies with synthetic 

Fe(III) oxides. 

A key implication of these findings is that production of Fe(II)-enriched sediments during 

one-time (or periodic) stimulation of DMRB activity is not likely to permit efficient, 

long-term abiotic conversion of U(VI) to U(IV) in biogenic redox barriers designed to 

prevent far-field subsurface U(VI) migration. Instead, ongoing DMRB activity will be 

required to achieve maximal U(VI) reduction efficiency. 

The study of dissimilatory metal reducing bacteria (DMRB, the general class of which 

dissimilatory iron reducing bacteria are part) has recently led to some interesting 

nanoscience discoveries that may offer new directions for nanotechnology. While most 

biological oxidation-reduction reactions take place in the liquid phase using water soluble 

species, dissimilatory reductions require a process where the electron acceptor is a solid 

phase material. Understanding the details of this process has been the topic of much 

research, with the focus largely being on c-type (monomeric) cyctochromes (heme 

proteins generally bound in cell membranes) which are known to perform electron 

transport. In 2005, Derek Lovley, who discovered Geobacter in 1987, published research 

showing that conductive structures (known as pili or “microbial nanowires”) only a few 

nanometers wide but microns long, are produced by Geobacter, are electrically 

conductive, and are indicated as being involved in electron transport (Reguera 2005). 

Subsequently, an international group (Gorby 2006) showed that other bacteria can be 

induced to produce nanowires (as small as 10 nm in diameter, but can reach hundreds of 

microns in length) when kept in an oxygen-starved state, are electrically conductive, and 

that this behavior is not limited to DMRB but might be a common bacterial strategy for 

efficient electron transfer and energy distribution. When in a community, the bacterial 

nanowires can cross and touch, and may allow for sharing of electrons among a network 

of bacteria. Figure 21 illustrates the bacterial nanowire reaching across organisms, and 

Figure 22 depicts a close-up image of a nanowire. The nanowires have been of great 

interest as a potential production and supply method of nanowires for other applications 

(such as sensors, nano-electronic components), as the basis of a possible remedial 

treatment approach, or as a component of microbial fuel cells. 
82 

Figure 21. Scanning electron microscope image of 

Shewanella ddeinensis strain MR-1 

Figure 22. Scanning Tunneling Microscope (STM) images of isolated nanowires 

from wild-type MR-1, with lateral diameter of 100 nm and a topographic height of 

between 5 and 10 nm. Arrows indicate the location of a nanowire and a step on the 

graphite 
83 

In summary, the literature on microbially mediated reduction of U(VI) showed that U(VI) 

can be reduced to U(IV) by enzymatic activity of microorganisms, including: 

• metal- and sulfate-reducing bacteria; 

• U(VI) can be reduced either by pure cultures or by mixed indigenous cultures; 

• U(IV) precipitates as uraninite (UO2); 

• complexation of U(VI) with organic and inorganic ligands can inhibit its 

reduction by microorganisms; and 

• complexation of U(IV) may inhibit its precipitation. 

Uranium reduction by bacteria is an example of bioremediation. As its advocates point 

out, bioremediation may be regarded as the oldest environmental technology of all, 

having existed virtually as long as the human species. Prior to 1989, bioremediation as a 

formal environmental technology was not widely known; it had a small number of 

advocates, though its claims were backed by considerable laboratory and academic work. 

The March 1989 Exxon Valdez disaster in Alaska and the subsequent use of 

bioremediation using naturally occurring marine organisms together with added nutrients, 

opened the way for bioremediation to become an established environmental remediation 

option. Economically, bioremediation usually offers great overall cost savings compared 

to competing technologies. In addition, risks tend to be smaller since contaminants are 

not transferred from one medium to another for processing, and there is no waste 

transportation involved. On the other hand, the bioremediation process may take much 

longer than chemical or physical treatment alternatives, requiring ongoing monitoring to 

ensure that progress is being made. When geological conditions are suitable and 

sufficient time is available, bacterial reduction of uranium is likely to be an attractive 

remedial alternative. 

 

2.7.1 References 

Abdelouas, A., W. Lutze, H. E. Nuttall. 1999a. Chapter 9: Uranium Contamination in the 

Subsurface: Characterization and Remediation. In Uranium: Mineralogy, Geochemistry, 

and Environment. P. C. Burns and R. Finch, (Eds.). Reviews in Mineralogy. 38: 433-473. 

Anderson, R.T., H.A. Vrionis, I. Ortiz-Bernad, .T. Resch, .E. Long, R. Dayvault, K. 

Karp, S. Marutzky, D.R. Metzler, A. Peacock, D.C. White, M.Lowe, D.R. Lovley. 2003. 

Stimulated in situ removal of U(VI) from groundwater of a uranium-contaminated 

aquifer. Applied and Environmental Microbiology. 69(10): 5884-5891. 

 

Dexter-Dyer, B., M. Kretzschmar, W.E. Krumbein.1894. Possible microbial pathways in 

the formation of Precambrian ore deposits. Journal of the Geological Society. 141 (2): 

251-262. 

Edwards L., K. Küsel, H. Drake, J.E. Kostka. 2007. Electron flow in acidic subsurface 

sediments co-contaminated with nitrate and uranium. Geochimica et Cosmochimica Acta.

71(3): 643-654. 
84 

Gorby, Y.A., S. Yanina, J.S. McLean, K.M. Rosso, D.Moyles, A. Dohnalkova, T.J. 

Beveridge, I.S. Chang, B.H. Kim, K.S. Kim, D.E. Culley, S.B. Reed, M.F. Romine, D.A. 

Saffarini|, E.A. Hill, L. Shi, D.A. Elias, D.W. Kennedy, G. Pinchuk, K. Watanabe, S. 

Ishii, B. Logan, K.H. Nealson, J.K. Fredrickson. 2006. Electrically conductive bacterial

nanowires produced by Shewanella oneidensis strain MR-1 and other microorganisms. 

Proceedings of the National Academy of Science. 103(30):11358-63.

Lovley D.R., E.J.P. Phillips, Y. Gorby, E. Landa. 1991. Microbial reduction of uranium. 

Nature. 350: 413-416. 

O’Loughlin, E.J., S.D. Kelly, R.E. Cook, R. Csencsits, K.M. Kemner. 2003. Reduction 

of uranium(VI) by mixed iron(II)/iron(III) hydroxide (green rust): formation of UO2 

Nanoparticles. Environmental Science and Technology. 37: 721-727. 

Quinton, G. E., R. J. Buchanan, D. E. Ellis, S. H. Shoemaker. 1997. A Method to 

Compare Groundwater Cleanup Technologies. Remediation. 7-16. 

Marshall, M.J., A.S. Beliaev, A.C. Dohnalkova, D.W. Kennedy, L. Shi, Z. Wang, M.I. 

Boyanov, B. Lai, K.M. Kemner, J.S. McLean, S.B. Reed, D.E. Culley, V.L. Bailey, C.J. 

Simonson, D.A. Saffarini, M.F. Romine, J.M. Zachara, J.K. Fredrickson. 2006. c-type 

cytochrome-dependent formation of U(IV) nanoparticles by Shewanella oneidensis.

Biology. 4(8):1324-1333. 

Reguera, G., K.D. McCarthy, T. Mehta, J.S. Nicoll, M.T. Tuominen, D.R. Lovley. 2005. 

Extracellular electron transfer via microbial nanowires. Nature. 435: 1098-1101. 

Roden, E.E., and M.O. Barnett. 2002. Reductive immobilization of U(VI) in Fe(III) 

oxide-reducing subsurface sediments: Analysis of coupled microbial-geochemical 

processes in experimental reactive transport systems. Final Scientific/Technical Report—

EMSP 73914, U.S. Department of Energy, Washington, DC. 

Talapatra, S., P.G. Ganesan, T. Kim, R. Vajtai, M. Huang, M. Shima, G. Ramanath, D. 

Srivastava, S.C. Deevi , P.M. Ajayan. 2005. Irradiation-Induced Magnetism in Carbon 

Nanostructures. Physical Review Letters. 95: 097201. 

Travis, C. C. and C. B. Doty. 1990. Can Contaminated Aquifers at Superfund Sites be 

Remediated? Environmental Science Technology. 24: 1464-1466. 

Virginia Tech (2006, September 21). Particle Size Matters To Bacteria Ability To 

Immobilize Heavy Metals. ScienceDaily. Website. Accessed December 2007. 

http://www.sciencedaily.com/releases/2006/09/060915203321.htm. 
85 

2.8 Carbon Nanotubes (Fullerenes)

2.8.1 Background 

After long being available only in research-level quantities, commercial-scale C-60 

fullerene production at the “tons-per-year” level is now available. The price of larger 

fullerenes is still high and quantities available are still small. Commercial-scale 

production at affordable prices is the target of intense research; over 1,500 patents have 

been filed on various potential production technologies. No radionuclide remediation 

technology is currently available or apparently under consideration, though the concept 

has been discussed. Carbon nanotubes and fullerenes are of special interest since they 

have been subject of much research both as components in remediations systems (either 

as part of nano-composite membranes or as functionalized separation platforms), and as 

sensors (primarily through a field effect transition mechanism). They are also one of the 

icons of the nanotechnology age. 

2.8.2 Description 

Fullerenes (first discovered in 1985 by Robert Curl, Harold Kroto, and Richard Smalley), 

are a class of hollow, spherical, or ellipsoid molecules—composed entirely of carbon 

atoms—in a cage-like structure composed of pentagonal and hexagonal faces. They were 

named after the architect Richard Buckminster Fuller due to their similarity to his 

geodesic dome design, and are often referred to as “buckyballs”. Fullerenes were the 

seventh allotropic form of carbon to be discovered (together with the two forms of 

diamond, the two forms of graphite, chaoit, and carbon (IV)). Their discovery led to Curl, 

Kroto, and Smalley receiving the Nobel Prize for Chemistry in 1996. Figure 23 provides 

a graphical representation of the 60-carbon atom containing C-60 fullerene, and Figure 

24 illustrates a graphical representation of the 540-carbon atom containing C-540 

fullerene. 

Figure 23. C-60 fullerene
86 

Figure 24. C-540 fullerene

An infinite number of spherical fullerenes are believed to be able to exist. Known forms 

include C-60, C-70, C-76, C-84, C-240, and C-540. All fullerenes consist of 12 

pentagonal faces and a varying number of hexagonal faces. In general, for a fullerene C-n 

there will be 12 pentagonal faces and half of n minus 10 (n/2-10) hexagonal faces; thus, 

the C-60 fullerene has 12 pentagonal faces and 20 hexagonal faces. 

Fullerenes have a rich and complex chemistry (Stevens 1994, Kadish and Roff 2000, 

Taylor 1995, Andreoni 2000, Hirsch et al. 2005) that led to the publication of over 15,000 

academic papers within 15 years of their discovery. C-60 behaves like an electron 

deficient alkene, reacts readily with electron rich species, and participates in many 

reactions (including oxidations, reductions, nucleophilic additions, electrophilic 

additions, Diels-Alder reactions, and Friedel-Craft alkylations). This rich chemistry 

permits a wide range of fullerene functionalization and opens the way to designing 

functionalized fullerene for specific properties and purposes. 

A large number of applications have been suggested for basic fullerenes and their 

functionalized derivatives. Potential applications include organic photovoltaics, polymer 

electronics, antioxidants, biopharmaceuticals, antibacterials, HIV inhibition, catalysts, 

water purification, MRI agents, optical devices, scanning tunneling microscopy, and 

atomic force microscopy (Nano-C 2006, Tang 2005, Da Ros et al. 2001). 

Fullerenes have also been the subject of many studies related to radioactive materials. 

They are being extensively investigated as carrier species for medical radionuclides in 

cancer therapy (Saha et al. 2006, Dagani 2002, Braun 1999, Medical News Today 2005). 

It has been observed that in the combustion of coal, which contains small amounts of 

uranium, nanocrystals of the mineral uranitite are encased in fullerene-type cages. This 
87 

potentially provides an unanticipated pathway for radiation exposure (Utsunomiya et al. 

2002). They have also been explored as a technology for radioactive waste management. 

DOE has determined that there are three major isotopes contributing to public radiation 

dose as a consequence of radionuclide releases—iodine-129, technetium-99, and 

neptunium-237—and fullerenes have been investigated as a sorbent for iodine (Schmett 

2002). It is also worth noting that a structure closely related to fullerenes, the carbon 

nanohorn (Figure 25), has been suggested as a possibility for radioactive waste disposal. 

Figure 25. The carbon nanohorn 

Though a vast amount of research has already been performed on basic carbon fullerenes, 

the real potential may lie in the fact that the work performed to date may only represent 

the tip of the iceberg. Many structures related to the basic fullerenes and the carbon 

nanohorn have been discovered. For example, the carbon nanocone (Figure 26) and 

“NanoBuds” (Figure 27) are relatively new materials developed by the Finnish company 

Canatu Oy (Canatu 2004, Nanowerk 2007) by combining carbon nanotubes and 

fullerenes. The resulting nanobuds possess properties of both materials (e.g., the 

electrical conductivity of carbon nanotubes with the chemical flexibility of fullerenes). 

Fullerene composites (Ltaief et al. 2006, Calleja et al. 1996, Barrera et al. 1994, Brabec et 

al. 1998, Eklund and Rao 2000, Prassides 2004) and hybrid materials, such as a fullerenedendrimer-mesoporous silica hybrid (Nierengarten et al. 2004), have been described. 
88 

Figure 26. The carbon nanocone 

Figure 27. Carbon nanobuds

Further, there exists a potentially enormous class of “inorganic fullerenes”. First 

described in 1992 (Materials Science Resource 2005), over 50 different types of 

inorganic fullerenes, and nanotubes have been reported in the technical and scientific 

literature, and include molybdenum sulfide, molybdenum selenide, tungsten sulfide, 

tungsten selenide, transition-metal chalcogenides, transition-metal oxides, transitionmetal halides, in addition to mixed-phase, metal-doped, boron-based, silicon-based, and 

pure metal nanotubes (Sano et al. 2003, Lvayen et al. 2007, Fu et al. 2005, Parilla et al. 

2004, Xia et al. 2004, Remskar et al. 2001, Parilla et al. 1999, Halford 2005), and “onionlike” fullerenes consisting of cages nested within other cages like Russian dolls (Cabio’h 

et al. 2005, Golberg et al. 1999). 
89 

2.8.3 Operational Considerations 

As one of the longest known and most intensely investigated type of nanoparticle, 

fullerenes have been the subject of much study in terms of fate and transport. However, 

there is little consensus, other than the need for more research (Zepp and Westerhoff 

2007, Wenger 2007, EIMS 2006, Handy and Owen 2006, Boxall 2007, Baalusha 2007, 

SETAC 2007, Drobne 2007). Recently, the results on investigations into the role of C-60 

nanoparticles in relation to toxicity and bioaccumulation of xenobiotic organic 

compounds in Daphnia magna were presented (Johansen et al. 2007). The hypothesis 

was that C-60 nanoparticles may act as carriers of xenobiotic organic chemicals 

(nanovectors), but mixed results were observed and are detailed below. 

• There was an increase in algal toxicity of atrazine with C-60 present; no changes 

in toxicity of methylparathion towards algae and daphnia. 

• There was a decrease in the toxicity of pentachlorophenol (PCP) towards algae 

and daphnia after addition to C-60 suspensions. 

• There was an increase in the toxicity of phenanthrene towards algae and daphnia 

in C-60 suspensions since the sorbed phenanthrene is bioavailable. 

• The uptake and excretion rates of phenanthrene and PCP were not significantly 

affected by addition to C-60 suspensions. 

Also, results on investigations into the effects of C-60 fullerene nanoparticles on soil 

bacteria and protozoa (Johansen et al. 2007) showed that fullerenes seem to have no, or 

only moderate, effects on the soil microbial community (regarding the number and 

viability of bacteria and protozoa). The genetic diversity of bacteria and protozoa seems 

to be altered slightly, but the mechanism behind the diversity changing effect is unclear 

(possible direct toxic effects on some of the microorganisms or indirect effects by 

sorption of nutrient or inhibiting factors in the soil). The conclusion was that since 

various fullerenes are very recalcitrant, and their production is expected to increase to 

very large quantities, it is important that their fate and ecotoxicology in complex 

environmental matrices be evaluated thoroughly in regards to transport, degradation, 

toxicology, and interactions with xenobiotics, and that there is a need for standardized 

methods for exposure of nanomaterials to organisms in vitro and in more complex 

systems. 

 

2.8.4 Summary of Environmental Potential 

 

Carbon nanotubes, and closely related materials, such as carbon nanohorns and carbon 

nanobuds, combine unique properties per se (such as greatly enhanced flow rates of water 

through the inside of the tubes over what would be expected from current theories) with 

the broad potential that results from a rich and complex chemistry. The range of 

applications is similarly wide, including both the development of advanced separatory 

processes (such as nanofiltration and reverse osmosis) and the development of nanoenabled sensors with the carbon nanotube acting as the sensing element. Carbon 

nanotubes have already been investigated for application to DOE’s three major problem 

isotopes (iodine-129, technetium-99 and neptunium-237) contributing to public radiation 
90 

dose. Carbon nanotubes are one of the longest known and most widely investigated type 

of nanoparticle, with research including hybrid products formed with other nanostructured materials (such as dendrimers). Given the extremely broad range of 

possibilities and the level of research interest, the likelihood of environmental 

technologies resulting from carbon nanotubes is assessed as very high. 

 

2.8.5 References 

Andreoni, W. (Ed.). 2000. The Physics of Fullerene-Based and Fullerene-Related 

Materials. Klewer Academic Publishers, The Netherlands. 

Baalusha, M. 2007. The existing toxicity test with a terrestrial isopod Porcellio scaber is a 

satisfactory starting point for assessing effects of nanoparticles. Presented at the SETAC 

Europe Annual Meeting. May 18, 2007. 

Accessed at http://se.setac.org/files/setac-eu-0121-2007.pdf. 

Barrera, E.V., J. Sims, D.L. Callahan, V. Provenzano, J. Milliken, R.L. Holtz. 1994. 

Processing of fullerene-reinforced composites. Journal of Materials Resources. 9(10): 

2662-2669. 

Boxall, Alistair. 2007. Current and predicted environmental exposure arising from 

engineered nanomaterials. Presented at SETAC Europe Annual Meeting. June 15, 2007. 

http://se.setac.org/files/setac-eu-0273-2007.pdf. 

Brabec, C.J., V. Dyakonov, N.S. Sariciftci, W. Graupner, G. Leising, J.C. Hummelen. 

1998. Investigation of photoexcitations of conjugated polymer/fullerene composites 

embedded in conventional polymers. Journal of Chemical Physics. 109(3): 1185-1195. 

Cabio’h, T., J.P. Riviere and J. Delafond. 2005. A new technique for fullerene onion 

formation. Journal of Materials Science. 30(19): 4787-4792. 

Calleja, F.J., L. Giri, T. Asano, Ti. Mieno, A. Sakurai, M. Ohnuma, and C. Sawatari. 

1996. Structure and mechanical properties of polyethylene-fullerene composites. Journal 

of Materials Science. 31(19): 5153-5157. 

Canatu. 2007. Nanobuds. Website. Accessed October 2007. 

http://www.canatu.com/nanobuds.html. 

Da Ros, T., G. Spalluto, M. Prato. 2001. Biological Applications of Fullerene 

Derivatives: A Brief Overview. Website. Accessed October 2007. 

http://www.vnovak.hr/ccacaa/CCA-PDF/cca2001/v74-n4/cca_74_2001_743-755_Da-Ros.pdf.

Dagani, Ron. 2002. Exotic Fullerene: Synthesis of metallofullerene derivative brings 

medical applications closer. Chemical and Engineering News. 80(4):15. Website. 

Accessed October 2007. http://pubs.acs.org/cen/topstory/8004/8004notw7.html. 
91 

Drobne, Damjana. 2007. Toxicity of nanoparticles to embryos of the marine macroalgae 

Fucus serratus. Presented at SETAC Europe Annual Meeting. June 15, 2007. Website. 

Accessed October 2007. http://se.setac.org/files/setac-eu-0274-2007.pdf.

EIMS Metadata Report. 2006. Fate and transport of carbon nanomaterials in 

unsaturdayted and saturated soils. 2006 Progress Report. Website. Accessed at 

http://oaspub.epa.gov/eims/eimsapi.dispdetail?deid=143629. 

Eklund, P.C. and A.M. Rao (Eds.). 2000. Fullerene Polymers and Fullerene Polymer 

Composites. Springer, Berlin. 

Fu, X., D. Wu, X. Zhou, H. Shi, Z. Hu. 2005. Solvothermal synthesis of molybdenum 

disulfide hollow spheres modified by Cyanex 301 in water-ethanol medium. Journal of 

Nanoparticle Research. 9(4): 675-681. 

Golberg, D. Y. Bando, K. Kurashima, T. Sasaki. 1999. Fullerene and onion formation 

under electron irradiation of boron-doped graphite. Carbon. 37(2): 293-299. 

Halford, Bethany. 2005. Unusual properties of nanotubes made from inorganic materials 

offer intriguing possibilities for applications. Chemical and Engineering News. 83(35): 

30-33. 

Handy, Richard, and Richard Owen. 2006. Environmental Effects of Nanoparticles and 

Nanomaterials Conference. September 18, 2006. Website. Accessed November 2007. 

http://www.setac-uk.org.uk/nano.pdf. 

Hirsch, A., M. Brettreich, F. Wudl. 2005. Fullerenes: Chemistry and Reactions. WileyVCH, Germany. 

Johansen, A., A. Pedersen, J. Scott-Fordsmand, A. Winding. 2007. Effects of C60 

fullerene nanoparticles on soil bacteria and protozoa. Presented at SETAC Europe 

Annual Meeting. June 15, 2007. Website. Accessed November 2007. 

http://se.setac.org/files/setac-eu-0275-2007.pdf. 

Kadish, K.M., and R.S. Roff (Eds.). 2000. Fullerenes: Chemistry, Physics, and 

Technology. Wiley-Interscience, Hoboken, New Jersey. 

Ltaief, A., A. Bouazizi, J. Davenas, P. Alcouffe, R. Ben Chaabane. 2006. Dielectric 

behaviour of polymer-fullerene composites for organic solar cells. Thin Solid Films. 511-

512: 498-505. 

Lvayen, V., E. Benavente, C.M. Sotomayor Tores, G. Gonzalez. 2007. Inorganic 

Fullerenes: From lamellar Precursors to Functionalized Nanotubes. Sold State 

Phenomena. 121-123: 1-4. 
92 

Materials Science Resource. 2005. Reshef Tenne Named 2005 MRS Medalist for 

Inorganic Fullerenes. Website. Accessed October 2007. 

http://www.mrs.org/s_mrs/doc.asp?CID=2079&DID=166552

Medical News Today. 2005. Nanoparticle created as diagnostic, therapeutic agent; 

brain tumors targeted. Oct. 19, 2005. Website. Accessed October 2007. 

http://www.medicalnewstoday.com/articles/32245.php. 

Nano-C. 2006. Fullerene Applications. Website. Accessed October 2007. 

http://nano-c.com/fullereneapp.html. 

Nanowerk. 2007. Novel carbon nanomaterial combines benefits of fullerenes and 

nanotubes. Website. Accessed October 2007. 

http://www.nanowerk.com/spotlight/spotid=1561.php. 

Nierengarten, J., M. Guttierez-Nava, S. Zhang, P. Masson, L. Oswald, C. Bourgogne, Y. 

Rio, G. Accorsi, N. Armaroli, S. Setayesh. 2004. Fullerene-containing macromolecules 

for materials science applications. Carbon. 42(5-6). 

Parilla P.A., A. C. Dillon, K. M. Jones, G. Riker, D. L. Schulz, D. S. Ginley, M. J. Heben. 

1999. The first true inorganic fullerenes? Nature. 397(114). 

Parilla, P., A.C. Dillon, B. A. Parkinson, K.M. Jones, J. Alleman, G. Riker, D. S. Ginley, 

M. J. Heben. 2004. Formation of nanooctahedra in molybdenum disulfide and 

molybdenum diselenide using pulsed laser vaporization. Journal of Physical Chemistry 

B. 108(20): 6197-6207. 

Prassides, K. (2004). Fullerene-Based Materials. Springer, New York. 

Remskar, M., A. Mrzel, Z. Skraba, A. Jesih, M. Ceh, J. Dem ar, P. Stadelmann, F. Lévy, 

D. Mihailovic. 2001. Self-Assembly of Subnanometer-Diameter Single-Wall MoS2

Nanotubes. Science. 292(5516): 479-481.

Saha, S.K., D.P. Chowdhury, S.K. Das, R. Guin. 2006. Encapsulation of radioactive 

isotopes into C60 fullerene cage by recoil implantation technique. Nuclear Instruments 

and Methods in Physics Research Section B: Beam Interactions with Materials and 

Atoms. 243(2): 277-281. 

Sano, N., H. Wang, M. Chhowalla, I. Alexandrou, G.A.J. Amaratunga, M. Naito, T. 

Kanki. 2003. Fabrication of inorganic molybdenumdisulfide fullerenes by arc in water. 

Chemical Physics Letters. 368(3):331-337. 

Schmett, G.T. 2002. Immobilization of fission iodine by reaction with fullerene 

containing carbon compounds or insoluble natural organic matter. Dissertation. Website. 

Accessed October 2007. http://aaa.nevada.edu/pdffiles/thesisschmett.pdf. 
93 

SETAC. 2007. SETAC Europe 17th Annual Meeting Presentations. Website. Accessed 

October 2007. http://se.setac.org/

Stevens, P.W. 1994. Physics and Chemistry of Fullerenes. World Scientific Publishing 

Company, Singapore. 

Tang, J. 2005. The Discovery and Applications of Fullerenes. Literature Seminar. 

October 4, 2005, University of Alabama. Website. Accessed October 2007. 

http://bama.ua.edu/~chem/seminars/student_seminars/fall05/papers-f05/tang-sem.pdf. 

Taylor, R. 1995. The Chemistry of Fullerenes. World Scientific Publishing Company, 

Singapore. 

Utsunomiya, S., K.A. Jense, G.J. Keeler, R.C. Ewing. 2002. Uraninite and Fullerene in 

Atmospheric Particulates. Environmental Science & Technology. 36(23): 4943-4947. 

Wenger, Y. 2007. Toxicity at the nanoscale level in trout hepatocytes exposed to 

quantum dots- exploring a new realm of toxicity. Presented at SETAC Europe Annual 

Meeting. May 9, 2007. Website. Accessed November 2007. 

http://se.setac.org/files/setac-eu-0006-2007.pdf. 

Xia, J., Z. Xu, W. Chen, Q. Nie, G. Li. 2004. Preparation and characterization of 

tungsten-substituted molybdenum disulfide nanorods. Chemistry Letters. 33(6): 766. 

Zepp, R. and P. Westerhoff. 2007. Nanotechnology Fate and Transport of Engineered 

Nanomaterials. Sponsored by National Institutes for Health, National Institute of 

Environmental Health Sciences, Superfund Basic Research Program. Presented August 

16, 2007. Website. Accessed October 2007. 

http://www.clu-in.org/conf/tio/nano6_081607/prez/nano6_08_16_07_modifiedpdf.pdf. 
94 

3.0 Nano-Enabled Sensor Technologies 

3.1 Introduction 

3.1.1 Basics 

Nanosensors are chemical sensors possessing a nanoscale sensing element. A chemical 

sensor is a device capable of providing quantitative or semi-quantitative information on a 

chemical species (or analyte) through calibration, and then brought into direct contact 

with the species in its environment. According to the definition given by the International 

Union of Pure and Applied Chemistry (IUPAC), a chemical sensor is: 

 “A device that transforms chemical information, ranging from the 

concentration of a specific sample component to total composition 

analysis, into an analytically useful signal. The chemical information, 

mentioned above, may originate from a chemical reaction of the analyte or 

from a physical property of the system investigated. Chemical sensors 

contain two basic functional units: a receptor and a transducer part. Some 

sensors may include a separator which is, for example a membrane 

(IUPAC 1997).” 

The receptor part of a sensor is defined by IUPAC as: 

“The chemical information is transformed in it into a form of energy, 

which maybe measured by the transducer. The receptor part maybe based 

upon various principles: physical, chemical or biochemical (IUPAC 

1997).” 

The transducer part of a sensor is defined by IUPAC as a: 

“Device capable of transforming energy carrying the chemical information about 

the sample into a useful analytical signal (IUPAC 1997).” 

In addition, a sensor may include an output system, which processes the transducer 

output into a useable form and relays it to the outside world. In contrast to a sensor, a 

chemical analysis (or assay) method or system requires many more processing steps than 

simply bringing a device into contact with the analyte, and frequently involves the use of 

additional reagents. It is important that the receptor and transducer parts of a sensor are 

closely integrated. As an example of a receptor and transducer combination, imagine a 

very small, reed-like beam with a reflective surface, capable of vibration that can be 

measured by a laser. In its basic state, the beam will vibrate with one frequency. If part of 

the surface of the beam is covered with a ligand that will bind highly selectively with a 

target analyte, then in the absence of the analyte, it will vibrate with a second, different 

frequency; in the presence of the analyte, it will vibrate with a third, yet again different 

frequency that is a function of the analyte concentration. In this scheme the ligand is the 

receptor and the beam/laser system is the transducer; the sensor operates by optical 
95 

transduction of a chemical binding event. Receptor events may be transduced by 

electrical, electrochemical, piezoelectrical, optical, magnetic thermal, mass sensitive, or 

other means. 

3.1.2 Chemical Sensors 

Chemical sensors are used in many settings, including: 

• Medical and health care arena for clinical diagnosis, drug screening, etc.; 

• Pharmaceutical development, biotechnology, microbiology, bacteriology, 

virology, genomics, and proteomics research; 

• A vast range of industrial process control; 

• Industrial effluent and pollution control; 

• Safety; 

• Environmental monitoring; and 

• Defense and security (chemical and biological weapons, explosives, and narcotics 

detection). 

The United States chemical sensor market is valued at approximately $3 billion per year, 

of which between one half and two thirds is for medical diagnostics, and much of the 

remainder is for gas sensors. The market is growing; this is a result of past sensor 

development research and, in turn, is contributing to current and future research for even 

better sensors. The characteristics of an ideal chemical sensor include: 

• Inexpensive—advantageous on its own merits and allows use of multiple 

detectors in arrays; 

• Low operating costs; 

• Robust; 

• Reliable; 

• Reversible; 

• Continuously useable; 

• High specificity; 

• High selectivity; 

• High sensitivity; 

• High accuracy; 

• Repeatability; 

• Fast speed of response; 

• Broad dynamic range; 

• Insensitivity to (or ability to compensate for) interference by factors such as 

temperature, pH, ionic strength, electrical and magnetic fields, etc.; 

• Small size for in-situ (biological or geological use); and 

• Minimal perturbation of the sample. 

Nanotechnology offers the promise of providing nanosensors capable of achieving many 

of these ideal characteristics, particularly those associated with speed, selectivity, 
96 

sensitivity, and size reduction. As a consequence, nanosensor development is one of the 

most active areas in the whole of nanotechnology. There are a number of major drivers 

for this activity. The first is miniaturization of sensors, which has been a pronounced 

trend in sensor development for the past 50 years. Some advantages of miniaturization 

are obvious. Smaller size: 

• leads to less material used in fabrication, enabling mass production contributing to 

lower cost and broadening market availability. 

• leads to reductions in weight and power consumption, which dramatically 

increase the versatility and range of options for use, and 

• permits reduction of sample size and decrease in any reagent consumption. 

3.1.3 The Trend towards Miniaturization 

All of the preceding factors have encouraged the trend towards microsensors over the 

past decades, but the move to the nanoscale invites factors beyond the simple 

continuation of miniaturization. 

• First, the new properties that are realized at the nanoscale and that have been 

partly discussed in earlier sections can be used in either the receptor or transducer 

parts of the sensor. 

• A second nanoscale factor is that there are some inherent benefits in working 

directly at the molecular level where the sensing phenomena take place. 

A study that directly asked the question of whether smaller is better for sensors 

(Kopelman and Dourado 1996) examined optical sensors and formalized the specific 

advantages of having nanoscale dimension sensors. In most instances, there is an explicit 

functional dependence of optode characteristics on the sensor radius (r), with the absolute 

detection limit decreasing with the cube of the radius (r3

), and the response time 

decreasing with the square of the radius (r2). Other features that improve, as sensors get 

smaller, include sample volume, sensitivity, invasiveness, spatial resolution, dissipation 

of heat in sensor and/or sample, and materials cost. A third nanoscale factor is that 

fabrication advances in the semiconductor and related industries, together with the 

coming of control of fluids on the microscale, has allowed the integration of many 

laboratory processing steps into a single device, and given rise to the concept and 

implementation of the LOC discussed in Section 3.2. 

The development of the LOC is directly related to a second major driver of nanosensor 

development—the analytical needs of the biotechnological and biomedical industries. 

Across many areas of biologically-related research, including the enormous areas of 

pharmaceutical and proteomic research, there is a need for cellular-level and massivethroughput analytical and sensing capabilities. The large-scale, low-cost manufacturing 

potential for nanosensors, and the greatly reduced reagent demands associated with 

sample preparation in their use, make them extremely attractive tools. In the medical 

field, early detection and diagnosis can greatly reduce the cost of patient care associated 
97 

with advanced stages of many diseases. Similarly, point-of-care sample analysis and realtime diagnosis can provide major savings for treatment of less serious conditions. 

An additional issue, not so much a driver for sensor development, but rather an enabling 

aspect in comparison with the development of remedial technologies, is the comparative 

ease of sensor development. Past experience, particularly in federal agencies with 

environmental responsibilities (such as EPA, DOE, and Department of Defense (DoD)), 

indicates that, generally, the time to maturity for a sensor development project (i.e., the 

duration of the entire effort from initial idea, through proof-of-concept, scientific 

development, engineering development, prototyping, demonstration, and deployment) is 

considerably shorter and less complex than the time to maturity for a remedial technology 

development project. Further, in terms of market penetration, or the transition from first 

being commercially available to being widely deployed, the timeline is shorter and the 

regulatory hurdles are much lower. Since the risks associated with sensors are much 

smaller than with remedial technologies and the development costs are smaller, even 

when allowance is made for the shorter development time, environmental sensors are a 

much more attractive investment than remedial technologies. This situation is likely to 

apply to nanotechnologies, as well as to conventional technologies. 

3.1.4 Opportunities 

In the environmental area (in general) and the remediation of radionuclides (in 

particular), there is a marked need for sensors with: 

• lower fixed and operating costs; 

• better performance in terms of sensitivity and specificity; and 

• more versatility in terms of portability and field operability. 

Control of remedial processes, contaminant detection, compliance monitoring, and 

environmental decision-making should all benefit from sensors with molecular level 

detection and improved overall performance. Current methods are costly, time-intensive, 

and limited (Sandia 2005). The use of in-situ or field operable sensors eliminates risks 

and costs associated with sample collection, handling, custody, transport, and storage. 

DOE’s Savannah River Site requires manual collection of nearly 40,000 groundwater 

samples per year, with a cost of between $100 and $1,000 per sample for off-site analysis 

(Looney and Falta 2000). 

It is anticipated that nanotechnology will have a bigger impact in providing sensors for 

radionuclide remediation than it will in providing remedial technologies, due to: 

• the well-structured basic understanding of sensor technology development; 

• the shorter, less expensive timelines for sensor development; and 

• the existing level of activity surrounding nanoscale sensor development. 
98 

The number of development efforts for radionuclide sensors is still very small, but this is 

because most efforts are being put into the medical and biotechnology areas, where there 

is a much larger potential market. Given our level of understanding of how receptors are 

integral to sensors and our level of understanding of how to design receptors for 

radionuclide species, it is a small extrapolation from the current, biologically oriented 

state-of-the-science to a future state-of-the-science, where radionuclide sensors can be 

easily realized. The following sections describe sensor technologies, or technology 

concepts, that can be comfortably extrapolated to radionuclides. As with Section 2 on 

remedial technologies, since extrapolation is involved, the survey cannot be 

comprehensive but rather seeks to provide information on reasonable possibilities that 

may yield sensor technologies in the near future. 

3.1.5 References 

IUPAC. 1997. Compendium of Analytical Nomenclature—Definitive Rules 1997, 3rd

Edition. Chapter 7, Section 4. Prepared for Publication by Janos Inczedy, Tamas Lengyel, 

and Allan M. Ure (Eds.). International Union of Pure and Applied Chemistry, Research 

Triangle Park, North Carolina, USA. Website. Accessed November 2007. 

http://www.iupac.org/publications/analytical_compendium/Cha07sec4.pdf 

Kopelman, R. and S. Dourado. 1996. Is smaller better? - Scaling of characteristics with 

size of fiber-optic chemical and biochemical sensors. Proceedings in Society of PhotoOptical Instrumentation Engineers (SPIE). 2836, 2-11.

Sandia. 2005. Micro-Chemical Sensors for In situ Monitoring and Characterization of 

Volatile Contaminants. Website. Accessed December 2007. 

http://www.sandia.gov/sensor/MainPage.htm#Description. 

Looney, B.B. and R.W. Falta (eds.). 2000. Vadose Zone Science and Technology 

Solutions. Battelle Press, Columbus Ohio. 
99 

3.2 “Lab-on-a-Chip” 

A Lab-on-a-Chip (LOC) device, also known as a micro-total-analytical system 

(microTAS) or microfluidics device, is a device that can integrate miniaturized laboratory 

functions (such as separation and analysis of components of a mixture) on a single 

microprocessor chip using extremely small fluid volumes on the order of nanoliters to 

picoliters. From a technology categorization perspective, LOCs can be viewed as a subset 

of microelectromechanical systems (MEMS) and combine miniaturized or novel sensing 

systems, fluid flow control concepts from microfluidics, and the suite of fabrication 

techniques (such as material deposition, material removal, surface patterning, and 

electrical property modification) used by the semiconductor industry. 

Currently, the main commercial applications of LOCs are in the medical and 

biotechnological fields, where it is anticipated that developments so far are the heralds of 

a technological revolution. In the same way that miniaturization changed computers from 

machines of limited capabilities occupying large rooms to small and easily portable yet 

powerful technology of today, over a period of a few decades, medical, biotechnological, 

and chemical analysis is expected to move from room-sized laboratories to microchipbased devices housed in hand-held or small portable readout consoles. Figure 28 shows 

an example of an LOC device that was tested on the International Space Station in 2007. 

 

Figure 28: LOC device tested on the International Space Station in 2007 

At the heart of LOC devices are “chips”, ranging in size from a fingernail to a credit card, 

fabricated using processes adapted from the printed circuit industry such as lithography, 

chemical etching, and laser machining. Figure 29 illustrates an impression of the size of 

the chip. Figure 30 provides a functional diagram of LOCs. 
100 

Figure 29. A comparison of the size of LOCs 

Figure 30. Functional diagram of LOCs 

In a manner similar to the production of printed circuit boards using techniques such as 

embossing and molding, microstructures (such as channels for liquid flow and pits for 

mixing and reactions) are made on the chip by depositing layers of material on top of one 

another on a surface, then patterning and selectively removing material to form a feature. 

A flat top surface or lid is attached to enclose the channels or mixing pits, and reagents 

can be driven around the system by pneumatic, electromotive, or capillary systems. 

The LOC was first conceived by Michael Widner at Ciba-Geigy (now Novartis) in the 

1980s, described conceptually in 1990 (Manz et al. 1990) with a groundbreaking work 

being published in 1992 (Harrison et al. 1992). Further development occurred as a new 

area of discovery—microfluidics—was developed in the 1990s. Microfluidics is an 
101 

interdisciplinary field dealing with the behavior and control of extremely small volumes 

of fluids and the design of systems that use these small volumes. Though most commonly 

encountered in ink-jet printers, the vast majority of microfluidics applications have been 

in biotechnology research, and some experts even regard it as a branch of biotechnology. 

In some ways, Microfluidics parallels nanotechnology in that the behavior of fluids at the 

microscale can differ substantially from the behavior at the macroscale; phenomena such 

as surface tension, heat conduction, and fluidic resistance start to become important, and 

issues such as evaporation, absence of turbulent flow, and the threat posed by presence of 

air bubbles are critical to system design. 

Initially, much of the impetus for continued development of LOCs came from the Human 

Genome Project, a 13-year project coordinated by DOE and the National Institutes of 

Health (NIH) that began in 1990 and was completed in 2003. Currently, much of the 

impetus for the continued development of LOCs comes from the desire for point-of-care 

medical diagnostics, whether in the doctor’s office, on a spacecraft, or other remote 

location. Additionally, development research is driven by the continued need for 

miniaturization, both to reduce the costs and the environmental impacts of research 

(green analytical chemistry). The LOC concept, already significant, is still considered to 

be in its infancy. Development research continues in many areas. In the area of 

fabrication materials, LOCs constructed using soft lithography techniques, rather than 

silicon microchip fabrication processes, are being investigated. Soft lithography is an 

alternative to silicon-based micromachining that uses replica molding of nontraditional 

elastomeric materials to fabricate stamps and microfluidic channels. In an extension to the 

soft lithography approach, multilayer soft lithography, with which devices consisting of 

multiple layers may be fabricated from soft materials, is being used to build active 

microfluidic systems containing on/off valves, switching valves, and pumps entirely out 

of elastomer. The softness of these materials allows the device areas to be reduced by 

more than two orders of magnitude compared with silicon-based devices. The other 

advantages of soft lithography (such as rapid prototyping, ease of fabrication, and 

biocompatibility) are retained (Unger et al. 2000). 

Environmental LOCs are also being investigated. An environmental LOC project is being 

funded by EPA with objectives to create a novel, nanomaterial-based submersible 

microfluidic device, exploiting unique properties of metal nanoparticles and carbon 

nanotubes for rapidly, continuously, and economically monitoring different classes of 

priority pollutants. The project also seeks to understand the relationship between the 

physical and chemical properties of these nanomaterials and their observed behavior. The 

challenge addressed is to help transform the LOC concept to an effective environmental 

monitoring system, and involves the examination of nanoparticle and nanotube materials 

for the separation and detection processes, respectively (Wang 2007). In addition, the 

NIH is supporting the development of a point detection disposable LOC with built-in 

mercury precursor electrodes for heavy metal detection (Ahn 2006).

Within these development efforts, it is also recognized that for novel and innovative 

technologies, even those that have an established market presence, close communication 

between developers and future users is essential. For example, in the United Kingdom, 
102 

research collaboration between five leading universities in the healthcare technology 

assessment arena and a group of industrial partners—Multidisciplinary Assessment of 

Technology Centre for Healthcare (MATCH) —is conducting a survey of LOC point-ofcare device manufacturers. Point-of-care in this context is defined as “analytical testing 

performed outside the central pathology laboratory using a device or devices that can be 

easily transported to the vicinity of the patient” (MATCH 2006). The aim is to assess the 

value of LOC for the diagnosis of cardiac-related problems using case studies, and to 

develop methods to shorten the time and decrease the costs of LOC development. 

3.2.1 Summary of Environmental Potential 

 

The LOC has great potential for addressing environmental needs. The technology 

platform is mature and well-established, and as other nano-enabled sensing technologies 

are developed, integration into the LOC should be facile. The twin features of rapid 

sample throughput and field portability should make the LOC a valuable tool in filed 

operations, particularly in circumstances such as the EPA Triad approach, where realtime monitoring is required to guide the progress of remedial work. 

 

3.2.2 References 

Ahn, C.H. 2006. A Point Detection Disposable Lab-on-a-Chip With Built-in Mercury 

Precursor Electrodes For Heavy Metal Detection. Website. Accessed December 2007. 

www.biomems.uc.edu/sponsors/_index.html. 

Harrison, D.J., A. Manz, Z. Fan, H. Lüdi, H. M. Widmer. 1992. Capillary Electrophoresis 

and Sample Injection Systems Integrated on a Planar Glass Chip. Analytical Chemistry. 

64: 1926–1932. 

Manz, A., N. Graber, H.M. Widmer. 1990. Miniaturized total chemical analysis systems: 

A novel concept for chemical sensing. Sensors and Actuators B: Chemical. 1(1-6): 244-

248. 

Multidisciplinary Assessment of Technology Centre for Healthcare (MATCH). 2006. 

Industrial Survey on Cardiac Point-of-care. Website. Accessed December 2007. 

http://www.match.ac.uk/POCT_industrial_survey/index.jsp.

Unger, M.A, H.-P. Chou, T. Thorsen, A. Scherer, S.R. Quake. 2000. Monolithic 

Microfabricated Valves and Pumps by Multilayer Soft Lithography. Science. 288(5463): 

113-116. 

Wang, J. 2007. Nanomaterial-Based Microchip Assays for Continuous Environmental 

Monitoring. Grant number RD - 83090002-0. US E.P.A, Washington D.C. 

http://yosemite.epa.gov/oarm/igms_egf.nsf/fca67ba1d90470b585256fb6006df291/0a3daa

8868a19a7c85256f90002109b9!OpenDocument,www.nibib.nih.gov/.../1112April2006%

20POCT/FINAL%20book%20for%20NIBIB_after.pdf

 
103 

3.3 Microcantilever Sensors

Microcantilever sensors are a technology which may develop into sensing systems for 

radionuclides, or is at least an example showing the potential and emergence of a new 

generation of highly sophisticated but flexible sensors. From a mechanical engineering 

perspective, a cantilever is simply a beam supported at one end and capable of defined 

bending and vibrational behavior. A microcantilever is simply a very small cantilever, the 

properties of which can be understood from basic engineering principles. 

The microcantilever was first developed in 1986 (Binnig et al. 1986) for use in Atomic 

Force Microscopy (AFM), the premier tool for nanoscale imaging and measuring. In 

AFM, an extremely sharp microscale tip, (with a tip radius of a few nanometers) 

connected to the end of a microcantilever (up to 10 nm thick, about 500 nm wide and 

about 2,500 nm long, and fabricated from Si or Si3N4), is positioned extremely close to 

the surface of a sample and the sample, is then moved beneath the tip. Interactions 

between the surface of the sample and the end of the tip arising from atomic forces (such 

as Van der Waals force, electrostatic force, magnetic force, or capillary force) attract or 

repel the tip (depending on mode of operation) and bend the microcantilever. Reflecting a 

laser beam off the cantilever and monitoring the beam’s deflection with photodiode 

arrays measures the amount of bending. A graphical representation of the AFM sensing 

components is provided in Figure 31, and a Scanning Electron Micrograph of a 

microcantilever biosensor used for DNA detection is shown in Figure 32. 

Figure 31. Principle of operation of the atomic force microscope 
104 

Figure 32. Scanning electron micrograph of fabricated microcantilever biosensor 

used for DNA detection 

The microcantilever is the simplest MEMS device. Early work soon demonstrated the 

versatility of the device in AFMs, with the microcantilever able to perform in air, liquid, 

or vacuum and across a range of temperatures. It also demonstrated the extreme 

sensitivity of the AFM to environmental effects and impurities, and the need to control 

these in making accurate measurements. However, studies on overcoming these issues 

also showed that the sensitivity of AFM to these environmental factors could be turned 

around, allowing the AFM to be a sensor for these same factors. For example, a 

microcantilever fabricated from silicon and coated with an aluminum surface for 

reflection of the laser beam can act as a “bimetallic strip” and respond to temperature 

changes. If a thermal event takes place on the cantilever surface, the silicon and 

aluminum expand to different extents and the cantilever bends, allowing the cantilever to 

act as a calorimeter of near-ultimate sensitivity. Similarly, if the microcantilever is given 

an absorbent coating that can attract water and is allowed to vibrate in dry air, it will have 

a natural frequency of vibration; changes in humidity change the mass of the 

microcantilever, and thus change the frequency of vibration, allowing it to act as a 

humidity sensor. From this, it is a short step to the concept of coating the microcantilever 

with a chemical functionality that binds selectively with a target analyte. In the absence 

of the analyte, the microcantilever vibrates with one frequency, while in the presence of 

the analyte, binding with the microcantilever coating occurs and vibration takes place at a 

frequency directly related to the degree of analyte binding—hence concentration. 

A related sensing mode is that the surface of the microcantilever can be coated with a 

layer of material that contains the chemical functionality able to bind selectively with a 
105 

target analyte. If this layer expands or contracts as the analyte is bound, then bending of 

the microcantilever occurs in a manner analogous to that of the bimetallic strip used for 

thermal sensing. The degree of bending is directly related to analyte concentration. This 

behavior was the basis of a microcantilever radionuclide sensor development project at 

ORNL. As described in Section 2.3 on SAMMS, if a head group at the end of a long 

organic chain molecule can interact strongly with a substrate, then a closely packed 

molecular monolayer of the chain molecules aligned with the chains pointing outwards 

from the substrate surface can form spontaneously when the two are brought into contact. 

The tail end of the organic chain can be functionalized prior to, or after, self-assembly 

using chemical functionalities selective for a targeted species. Thiol (S-H) head groups 

and a gold substrate form an excellent pairing for this type of behavior, and the self 

assembly of alkanethiols has been observed to produce surface stress in the gold substrate 

(Berger et al. 1997). 

Silicon and closely-related materials have been the main materials of construction for 

microcantilevers. Silicon has been recognized as an outstanding mechanical material for 

over a quarter of a century (Petersen 1982). However, silicon is not the only fabrication 

material under investigation. Chemical sensing with micromolded plastic cantilevers and 

production issues have been explored (McFarland and Colton 2005). 

In addition to microcantilevers based on silicon, plastics; and related materials, 

nanostructures (such as single-walled carbon nanotubes (SWCNT)) have been explored 

for gas-sensing applications (Hsu 2007). The approach uses the fact that SWCNTs are 

capable of interacting with the gaseous species—either directly through surface 

adsorbtion, or indirectly by using a polymer analyte coated on its surface—and the higher 

surface-to-bulk ratio available with a nanostructure leads to higher sensitivity and shorter 

response time. As with other microcantilevers, the effect of bound or adsorbed species is 

manifested either as a change in resonant frequency (which can be detected by using a 

Wheatstone bridge circuit), or as an increased surface stress (which can be detected by 

measuring the change in the capacitance value through comparison with a specific 

reference capacitor). Hsu’s work involved successful simulation, fabrication, and 

manipulation of the SWCNT; development and simulation of a capacitive sensing circuit 

layout; and consideration of packaging and integration issues, including use of a 

“nanoglue” developed at Rensselaer Polytechnic Institute, based on the processing of a 

self-assembled molecular monolayer and capability of bonding completely dissimilar 

materials. 

Among the drivers for further development was the widespread need for portable, realtime, in-situ chemical, physical, and radiological sensors in a variety of applications 

including the characterization and monitoring of mixed waste, ground water, 

contaminated soil, and process streams. Microcantilever-based sensors were recognized 

as a potential solution for this need. They also provide excellent sensitivity for important 

metal ions in solution such as Hg2+, CrO4

2-, Sr2+, and TcO4-. The ability of the 

microcantilever to detect cesium (Thundat et al. 1999, Ji et al. 2000a) (though 

irreversibility problems were observed) and chromate (Ji et al. 2000b) was demonstrated; 
106 

concentrations below the parts per billion level were obtained with exceptional selectivity 

even in the presence of other interferences. 

Fundamental microcantilever research at ORNL showed that adsorption-induced changes 

in the spring constant of a cantilever, leading to errors in the calculation of adsorbed mass 

from shifts in resonance frequency (Thundat 2002). Simultaneous measurement of 

resonance frequency and adsorption-induced bending was shown to allow the change in 

spring constant to be determined. A silicon microcantilever with gold coating on one side 

was found to respond selectively and sensitively to Hg(II) ions in solution, and while 

modification of the Si surface with a silane reagent did not change the response to Hg, 

modification of the gold surface with octanethiol greatly retarded the rate of deflection, 

indicating the Hg(II) is reacting with the gold surface. The surface charge on the goldsolution interface is postulated to reduce Hg(II) to a surface amalgam. Modification of 

the gold surface with a monolayer 1,6-hexanedithiol makes the surface sensitive and 

selective for (CH3)Hg+ adsorption-induced deflection. Na+, K+, Pb2+, Zn2+, Cd2+, Ca2+, 

and Ni2+ in solution do not interfere with the response of the microcantilever to Hg. Gold 

coated cantilevers with chemically modified surfaces respond sensitively to Ca2+ ions at a 

concentration of 10-9 M. The sorption of a monolayer of 2-(4-mercaptophenoxy)-N, Ndiethyl-acetamide, as well as the agent bis (11-mercaptoundecyl) phosphate were shown 

to detect Ca2+ ions, although the former was more selective. A self-assembled monolayer 

of L-cysteine on a cantilever coated with gold on one side was shown to be effective for 

the detection of a concentration of 10-10 M Cu2+. Both the Ca2+ and the Cu2+ were 

relatively free from interference by each other and Na+

, K+, Pb2+, Zn2+, Cd2+, and Ni2 in 

solution (Thundat 2002).

 

Subsequent work showed that electrochemically-active metal ions (Cu, Cr, Hg and Pb) 

could be detected by the novel approach of using a cantilever as a working electrode 

since electrodeposition of electro-active metal ions on cantilever surface results in 

cantilever bending. Together with the observation that that the cantilever bending is 

extremely sensitive to electrochemical current in the solution, this has led to the 

development of a technique where the cantilever serves as a reference/counter electrode 

for electrochemical reactions occurring on another working electrode (Thundat et al. 

2006), with work continuing towards the development of field-deployable, miniature 

sensors with extremely high sensitivity, exceptional selectivity, and the ability to be 

integrated into a wireless communication system that will allow real-time data to be 

provided on concentration and speciation of multiple contaminants and their variation 

with time. 

Work has also continued on microcantilevers functionalized with metal-binding moieties. 

Gold-coated sides of silicon nitride microcantilevers functionalized with the metalbinding protein AgNt84-6 have been demonstrated to be sensors for the detection of 

heavy metal ions, such as Hg2+ and Zn2+ (Cherian et al. 2003). On exposure to HgCl2 and 

ZnCl2 solutions, the microcantilevers underwent bending corresponding to an expanding 

gold side, while exposure to MnCl2 solution did not result in a similar bending, indicating 

a weak or lacking interaction of Mn2+ ions with the AgNt84-6 protein. The 

microcantilever bending data were consistent with data from electrophoresis that showed 
107 

protein interaction with Zn2+ ions but not with Mn2+ ions, demonstrating that 

microcantilever bending can be used to discriminate between metal ions that bind and do 

not bind to AgNt84-6 protein in real time. 

3.3.1 Summary of Environmental Potential 

 

Microcantilever sensors are one of the few nano-sensor technologies that have already 

been investigated with the detection of radioactive species in mind. The technology is 

very flexible; all that is needed for detection of a species is a coating with a chemical 

functionality capable of binding the target species. The technology is well-established, 

reliable, and sensitive—its origin in the AFM makes it a gateway technology for the 

nanotechnology age—and is easily integrated into the LOC platform. The versatility of 

the technique is further expanded by the fact that many materials, including innovative 

nanomaterials such as carbon nanotubes, may be usable as the cantilever. 

 

3.3.2 References 

Berger, R., E. Delamarche, H.P. Lang, Ch. Gerber, J.K. Gimzewski, E. Meyer, H.-J. 

Güntherodt. 1997. Surface stress in the self-assembly of alkanethiols on gold. Science. 

276: 2021-2024. 

Binnig, G., C.F. Quate, C. Gerber. 1986. Physics Review Letters. 56: 930–933. 

Cherian, S., R. K. Gupta, B. C. Mullin and T. Thundat. 2003. Detection of heavy metal 

ions using protein-functionalized microcantilever sensors. Biosensors and Bioelectronics.

19(15) 411-416. 

Hsu. J.C. 2007. Fabrication of Single Walled Carbon Nanotube (SW-CNT) Cantilevers 

for Chemical Sensing. Thesis for Master of Science in Electrical Engineering (etd11082007-103811), Louisiana State University, May 2007. 

Ji, H.-F., E. Finot, R. Dabestani, T. Thundat, G. M. Brown, P. F. Britt. 2000a. A Novel 

Self-Assembled Monolayer (SAM) Coated Microcantilever for Low Level Cesium 

Detection. Chemical Communications. 457-458. 

Ji, H-F., T. G. Thundat, R. Dabestani, G. M. Brown, P. F. Britt, P. V. Bonnesen. 2000b. 

Ultrasensitive Detection of CrO4

2- Using a Microcantilever Sensor. Analytical Chemistry. 

73: 1572-1576. 

McFarland, A.W. and J.S. Colton. 2005. Chemical sensing with micromolded plastic 

microcantilevers. Journal of Microelectromechanical Systems. 14: 1375-85. 

Petersen, K. E. 1982. Silicon as a mechanical material. Proceedings of IEEE. 70: 420–

457. 
108 

Thundat, T., E. Finot, H-F. Ji, R. Dabestani, P. F. Britt, P. V. Bonnesen, G. M. Brown, R. 

J. Warmack. 1999. Highly Selective Microcantilever Sensor for Cesium Ion Detection. 

Proceedings of Electrochemical Society. 99(123) 314-319. 

Thundat, T.G. 2002. Microsensors for In situ Chemical, Physical, and Radiological 

Characterization of Mixed Waste. EMSP-73808-2002. U.S. DOE Environmental 

Management Science Program Report, Washington DC. 

Thundat, T.G., Z. Hu, G.M. Brown, B. Gu. 2006. Microcantilever Sensors for In situ 

Subsurface Characterization. 2006 ERSD Annual Report. Oak Ridge National 

Laboratory, Tennessee. 
109 

3.4 Spectroscopic Sensors 

Spectroscopy is the scientific study of the absorption, emission, or scattering of 

electromagnetic radiation by atoms, molecules, ions, solids, liquids, or gases. The 

underlying and unifying phenomenon behind all types of spectroscopy is that the 

interaction of electromagnetic radiation with any type of matter can cause transitions 

between quantized energy levels (often, though not always, electronic energy levels) of 

the atoms or molecules. Since so many of these transitions can occur and can be 

influenced and modified by other phenomena, spectroscopy provides the potential for 

enhanced chemical analysis and sensing. The list of spectroscopic techniques and subtechniques is large and continually increasing. A partial sampling of these techniques 

includes: 

• Absorption spectroscopy 

• Atomic absorption spectroscopy 

• Atomic emission spectroscopy 

• Atomic fluorescence spectroscopy 

• Attenuated total reflectance spectroscopy 

• Auger electron spectroscopy 

• Cavity-ringdown laser absorption spectroscopy 

• Electron paramagnetic spectroscopy 

• Electron spectroscopy 

• Electron spin resonance spectroscopy 

• Extended x-ray absorption fine structure spectroscopy 

• Fluorescence spectroscopy 

• Fluorescence correlation spectroscopy 

• Gamma-ray spectroscopy 

• Image correlation spectroscopy 

• Infrared spectroscopy 

• Intracavity-absorption spectroscopy 

• Laser spectroscopy 

• Laser-induced fluorescence 

• Mass spectrometry 

• Mossbauer spectroscopy 

• Nuclear magnetic resonance spectroscopy 

• Multiplex or frequency-modulated spectroscopy 

• Raman spectroscopy 

• Resonance-ionization spectroscopy 

• Tunable diode laser absorption spectroscopy 

• Surface-enhanced raman spectroscopy 

• UV-vis absorption spectroscopy 

• X-Ray spectroscopy 
110 

Phenomena based on nanoscale effects are being examined in and by many of these types 

of spectroscopy. Some examples include: 

• Nanosensors for nitric oxide using cytochromes have been examined and show a 

fast, reversible, and linear response up to 1 mM nitric oxide with a detection limit 

of 20 μM (Barker et al. 1998). 

• A fluorescence nanosensor for Cu2+ ions using surface functionalization of silica 

particles with trialkoxysilane derivatized ligand and fluorescent dye has been 

investigated (Brasola et al. 2003). 

• PEBBLE nanosensors, in the 20 to 200 nm size range, have been made for zinc 

detection using two fluorescent dyes (one sensitive to zinc and the other as a 

reference) localized in a polymer matrix by a microemulsion (Sumner et al. 2002). 

• A simple colorimetric technique for the detection of small concentrations of lead, 

cadmium, and mercury) using reversible chelation/aggregation process for 

functionalized gold nanoparticles has been developed (Kim et al. 2001). 

• A distributed Bragg reflector (a high-quality reflector used in waveguides and 

formed from multiple alternating layers of materials with varying refractive 

index) optical sensing element for organic solvents has been developed using 

stacks of Teflon®-like and gold nanoparticles. Absorption of organic vapors 

causes swelling of the composite and affects the reflectivity (Convertino et al. 

2004). 

• The first nanometer-scale anion sensing fluorescent spherical nanosensors have 

been developed (Brasuel et al. 2003). 

• A rapid and sensitive fluorescence immunoassay has been developed for the 

simultaneous detection and identification of multiple harmful microorganisms 

using dye-doped silica nanoparticle-antibody conjugates (Zhao et al. 2004). 

• The fabrication of submicron optical-fiber fluorescent sensors and particle-based 

fluorescent nanosensors has been reviewed, and the functional characteristics of 

miniaturized fluorescent sensors and their applications for quantitative 

measurement of intracellular analytes have been discussed (Lu and Resenzweig 

2004). 

• A nanoscale fluoroimmunoassay for the herbicide atrazine in an LOC has been 

developed using lanthanide oxide nanoparticle labels (Koivunen et al. 2004). 

As these examinations indicate, most spectroscopic sensing methods detect the binding of 

a target species to a receptor by incorporating a fluorescent moiety into the receptor and 

then examining the fluorescence behavior. Fluorescence spectroscopy analyzes the 

fluorescence of a material, where fluorescence is a non-thermally originating 

luminescence phenomenon in which a molecule or other species absorbs a photon at one 

wavelength (usually in the visible range), and then re-emits another photon with a longer 

wavelength (usually in the ultraviolet range), with the difference in energy between the 

two photons becoming thermal energy through vibrational relaxation. Fluorescence can 

now reach down to the single molecule detection level and is such a powerful technique 

that, over the past decade, it has become the dominant tool in biotechnology and medical 

imaging (Geddes 2005). The following two examples demonstrate nanotechnologies that 
111 

incorporate the fluorescence spectroscopy tool, PEBBLE and Surface Plasmon 

Resonance. 

3.4.1 Probe Encapsulated by Biologically Localized Embedding 

A nanotechnology that incorporates the fluorescence tool is PEBBLE. PEBBLE 

nanosensors are sub-micron sized optical sensors designed specifically for minimally 

invasive analyte monitoring in viable, single cells. PEBBLE is a general term that 

describes a family of matrices and nano-fabrication techniques used to miniaturize many 

existing optode technologies. The main classes of PEBBLE nanosensors are based on 

matrices of polyacrylamide hydrogel, sol gel silica, and cross-linked decyl methacrylate. 

These matrices have been used to fabricate sensors for H+

, Ca2+, K+, Na+, Mg2+, Zn2+, Cl-, 

NO2

-

, O2, NO, and glucose that range from 30 to 600 nm in size. A host of delivery 

techniques have been used to successfully deliver PEBBLE nanosensors into mouse cells 

(Monson et al. 2003, Park et al. 2003, Xu et al. 2001, Buck et al. 2004, Xu et al. 2002, 

Clark et al. 1999, Sumner et al. 2002). The PEBBLE nanosensor format offers the twin 

benefits of protecting fluorescent indicator dyes from interferents and allowing 

combination of multiple dyes, ionophores, and other components to create complex 

sensing schemes. It is the multifunctionality that is the main advantage of PEBBLE 

nanosensors for biological research. A conceptual representation is shown in Figure 33. 

Figure 33. Conceptual representation of the multifunctionality of PEBBLE 

nanosensors 

PEBBLE nanosensors were specifically developed for biological work since they have 

the advantages of a small size that permits intra-cellular biological measurements to be 
112 

made without causing cell mortality; a polymeric matrix able to contain a combination of 

indicator dyes, reference dyes, and catalysts (including some that might normally be toxic 

to the cell); fast response time; and the option of being calibrated by either ex-vivo or exvitro means. The use of both indicator dyes and reference dyes enables ratiometric 

fluorescent detection, which can correct for variations in excitation source intensity and 

minimizes the effects of photobleaching on quantitative measurements. 

3.4.2 Surface Plasmon Resonance 

While PEBBLE nanosensors offer a platform on which existing spectroscopic techniques 

can be mounted, a spectroscopy that offers great potential for chemical sensing and has 

achieved a much deeper understanding as a result of nanotechnology (specifically 

through the development of the new field of nanoparticle optics) is surface plasmon 

resonance (SPR) spectroscopy. 

Comprehension of SPR first requires an understanding of the plasmon phenomenon. In 

physics, photons are regarded as the particle equivalent of quantized electromagnetic 

waves. From solid-state physics, it is also commonly understood that the electrons in a 

metallic crystal can be successfully modeled as a quasi-ideal gas, or plasma.. Oscillations 

in the charge density of this quasi-ideal gas can occur, and when waves are quantized as 

standing waves then the particle equivalent is known as a plasmon. Surface plasmons are 

plasmons confined to the surface of a material or the interface of plasma-containing 

material with some other material. They propagate parallel to the material surface and are 

evanescent waves that decay exponentially with distance from that surface; they are thus 

very sensitive to any changes at the surface. Plasmons can be excited by coupling with 

incident light to give the phenomenon of surface plasmon resonance. 

Gold and silver are the classic metals for supporting surface plasmons, but metals such as 

copper, chromium, and titanium also support the phenomenon. When surface plasmon 

resonance is achieved on macroscale or mesoscale surfaces using very thin metal films, 

the plasmon wave can propagate across the surface for a distance of tens or hundreds of 

thousands of nanometers, but decays quickly as it moves outward from the surface. This 

is known as propagating surface plasmon resonance. Surface plasmon resonance can also 

be achieved on the nanoscale using metal nanoparticles, even though they are smaller 

than the wavelength of the light involved. In this case the plasmon wave oscillates locally 

around the nanoparticle. This manifestation of the phenomenon is called localized surface 

plasmon resonance (LSPR). A comprehensive review of LSPR spectroscopy and sensing 

is available (Willets and Van Duyne 2007). 

The primary consequences of LSPR resonance include (1) localized electromagnetic field 

enhancement that is responsible for the intense signals observed in surface-enhanced 

spectroscopies, and (2) selective photon absorption and scattering (collectively called 

extinction), which can be easily monitored using UV-vis spectroscopy (Haes and Van 

Duyne 2002). Regarding the extinction behavior, theoretical considerations of the optical 

properties of nanoparticles (Haes et al. 2004) indicates that there are at least four different 

nanoparticle-based sensing mechanisms for transducing chemical-binding events into 
113 

optical signals: (1) resonant Rayleigh scattering from nanoparticle labels (analogous to 

fluorescent dye labels); (2) nanoparticle aggregation behavior; (3) charge-transfer 

interactions at nanoparticle surfaces; and (4) local refractive index changes. The plasmon 

resonance phenomenon thus provides a variety of approaches for measuring its behavior 

that can be exploited in the development of sensors. 

Changes to the surface have major effects on this resonance. It has been observed that 

solutions of certain nanoparticles (e.g., gold) can give rise to intense colors; as far back as 

the medieval period, artists working in stained glass used this effect (see Figure 34). The 

origin of this effect, which is not manifested in the bulk material, is the absorption of 

energy in the ultra-violet region of the spectrum as a result of surface plasmon resonance. 

Changes to the surface of the gold particles (e.g., the binding of DNA or other bio 

material) have noticeable and easily measurable effects on the frequency of the surface 

plasmon resonance, and can be used as a sensing mechanism. 

Figure 34. The colors in medieval stained glass are the result of surface plasmon 

resonance 

The most acclaimed use of LSPR spectroscopy using nanoparticles has been the detection 

of a biomarker for Alzheimer’s disease from synthetic and clinical samples (Haes and 

Van Duyne 2004, Haes et al. 2005). It has also been shown to detect small molecules, 

such as camphor (Zhao et al. 2006b). Further, with the appropriate recognition moiety, 

LSPR should be easily modifiable to detect metals and radionuclides. In fact, the 

feasibility of developing an SPR spectroscopy-based sensor, a technique very closely 

related, for a radioactive material (pertechnetate) has already been demonstrated 

(Anderson 2000). A previously developed fiber optic SPR sensor used for gas phase dew 

point determination was modified to liquid-phase sensing by placing a coating of 

polyethylene glycol (PEG, which has been used in aqueous biphasic extraction for 

removal of pertechnetate from Hanford and Oak Ridge tank waste) on an SPR system 
114 

consisting of a sapphire hemisphere coated with a thin gold film. The SPR sensor 

generated high-resolution, low-noise SPR spectra suitable for high sensitivity sensing of 

analyte adsorption onto the sensor surface, and was able to discriminate very small 

changes in refractive index and show a unique response to 10 ppm perrhenate in NaOH 

solution. 

3.4.3 Summary of Environmental Potential 

As a class, spectroscopic techniques (such as PEBBLEs, surface plasmon resonance, or 

sensing technologies based on nanobelts and nanorods) offer the possibility of detection 

capabilities down to the single molecule level. Sensing technologies for characterization 

and monitoring uses are of extreme importance in the environmental field—both for 

remediation and for process monitoring for pollution prevention applications. The 

flexibility that can be imparted to nano-enabled sensors means that a wide variety of 

species can be detected at the lowest levels, and creates a potentially large opportunity for 

these and similar technologies. 

3.4.4 References 

Anderson, B.B. 2000. Feasibility Study for the Development of a Surface Plasmon 

Resonance spectroscopy-based Sensor for the BNFL-Hanford. BNF-003-98-0308. U.S. 

Department of Energy Savannah River Site, Technical Report. 

Barker, S.L.R., R. Kopelman, M.A. Cusanovich. 1998. Fiber-Optic Nitric OxideSelective Biosensors and Nanosensors. Analytical Chemistry. 70(5): 971-976. 

Brasola E., F. Mancin, E. Rampazzo, P. Tecilla, U. Tonellato. 2003. A Fluorescence 

Nanosensor for Cu2+ on Silica Particles. Chemical Communications. 24: 3026-3027. 

Brasuel, M.G., T.J. Miller, R. Kopelman, M.A. Philbert. 2003. Liquid Polymer NanoPEBBLEs for Cl- Analysis and Biological Applications. Analyst. 128(10): 1262-1267. 

Buck, S.M., Y.E. Koo, E.J Park, H. Xu, M.A. Philbert, M. Brasuel, R. Kopelman. 2004. 

Optochemical nanosensor PEBBLEs: photonic explorers for bioanalysis with biologically 

localized embedding. Current Opinion Chemical Biology. 8(5):540-546. 

Clark, H.A., R. Kopelman, R. Tjalkens, M.A. Philbert. 1999. Optical nanosensors for 

chemical analysis inside single living cells. 2. Sensors for pH and calcium and the 

intracellular application of PEBBLE sensors. Analytical Chemistry. 71(21): 4837-4843. 

Convertino, A., A. Capobianchi, A. Valentini, E.N.M. Cirillo. 2004. High Reflectivity 

Bragg Reflectors Based on a Gold Nanoparticle/Teflon-Like Composite Material as a 

New Approach to the Organic Solvent Detection. Sensors and Actuators B: Chemical. 

100(1-2): 212-215. 

Geddes, C.D. 2005. Advanced Concepts in Fluorescence Sensing. Springer, New York. 
115 

Haes, A. J. and R. P. Van Duyne. 2002. A Highly Sensitive and Selective SurfaceEnhanced Nanobiosensor. Materials Research Society Symposium Proceedings. 723: 

O3.1.1-O3.1.6. 

Haes, A.J. and R. P. Van Duyne. 2004. A Unified View of Propagating and Localized 

Surface Plasmon Resonance Biosensors. Analytical and Bioanalytical Chemistry. 379: 

920-930. 

Haes, A. J., L. Chang, W.L. Klein, R. P. Van Duyne. 2005. Detection of a biomarker for 

Alzheimer’s disease from synthetic and clinical samples using a nanoscale optical 

biosensor. Journal of the American Chemical Society. 127:2264-2271. 

Kim, Y., R.C. Johnson, J.T. Hupp. Gold Nanoparticle-Based Sensing of 

"Spectroscopically Silent" Heavy Metal Ions. Nano Letters. 1(4): 165-167. 

Koivunen, M.E., M.E., S.J. Gee, I.M. Kennedy, B.D. Hammock. 2004. Nanoscale 

Fluoroimmunoassays with Lanthanide Oxide Nanoparticles: 'Lab-on-a-Chip'. 

Presentation (Abstract ANYL 194) at the 227th ACS National Meeting, Anaheim, CA. 

Lu, J. and Z. Rosenzweig. 2000. Nanoscale Fluorescent Sensors for Intracellular 

Analysis. Journal of Analytical Chemistry. 366(6-7): 569-575. 

Monson, E., M. Brasuel, M. Philbert, R. Kopelman. 2003. PEBBLE Nanosensors for in 

vitro Bioanalysis. In Biomedical Photonics Handbook. T. Vo-Dinh (Ed.) CRC Press, 

Boca Raton, Florida. 

Park, E.J., M. Brasuel, C. Behrend, M.A. Philbert, R. Kopelman. 2003. Ratiometric 

optical PEBBLE nanosensors for real-time magnesium ion concentrations inside viable 

cells. Analytical Chemistry. 75(15): 3784-91. 

Sumner, J.P., J.W.Aylott, E. Monson, R. Kopelman. 2002. A fluorescent PEBBLE 

nanosensor for intracellular free zinc. The Analyst. 127(1):11-16. 

Willets, K.A. and R.P. Van Duyne. 2007. Localized Surface Plasmon Resonance 

Spectroscopy and Sensing. Annual Review of Physical Chemistry. 58:267-297. 

Xu, H., J.W. Aylott, R. Kopelman, T.J. Miller, M.A. Philbert. 2001. A real-time 

ratiometric method for the determination of molecular oxygen inside living cells using 

sol-gel-based spherical optical nanosensors with applications to rat C6 glioma. Analytical 

Chemistry. 73(17): 4124-4133. 

Xu, H., J.W.Aylott, R. Kopelman. 2002. Fluorescent nano-PEBBLE sensors designed for 

intracellular glucose imaging. The Analyst. 127(11): 1471-1477. 
116 

Zhao, X., L.R. Hilliard, S.J. Mechery, Y. Wang, S. Jin, W. Tan. 2004. A rapid bioassay 

for single bacterial cell quantitation using bioconjugated nanoparticles. Proceedings of 

the National Academy of Sciences USA. 101(42): 15027-15032 

Zhao, Y.-P., S.-H. Li, S.B. Chaney, S. Shanmukh, J.-G. Fan, R.A. Dluhy, W. Kisaalita. 

2006. Designing Nanostructures for Sensor Applications. Journal of Electronic 

Materials. 35(5): 846. 
117 

3.5 Nanowire Sensors 

3.5.1 Background 

Nanowires are solid, rod-like materials with diameters in the 5-100 nm range, and are 

most often made from metals or semiconducting metal oxides. Nanowires are different 

from molecular wires (also sometimes referred to as “molecular nanowires”), which are 

molecular entities with diameters typically less than 3 nm and repeating subunits. DNA is 

the premier example of a molecular nanowire, with the repeating subunits being the 

constituent nucleotides; inorganic examples include Li2Mo6Se6 and Mo6S9-xIx. Research 

on nanowires is often conducted along with parallel research on carbon nanotubes. 

Though these materials are different, the sensing mechanisms and underlying behavior 

are usually very similar. However, it should be noted that there are significant differences 

in processing and scale-up potential; though similar devices may be made from these 

nanostructures, this does not mean that similar commercial products will eventually be 

available. 

3.5.2 Description 

Nanowire sensors have attracted much attention for two reasons. First, their large surface 

area to volume ratio promises high sensitivity. Second, the size of the nanostructures is 

similar to the size of species being sensed, thus the nanostructures make good candidate 

transducers for producing the signals that are then read and recorded by conventional 

instruments. The underlying phenomenon exploited in using nanowires is the field effect 

on which field effect transistors (FETs) are based. The wire acts as the channel from 

source to drain for the FET. If functional groups attached to the nanowire can act as a 

receptor to bind with a target species (particularly a biological entity that possesses a 

charge), then the charge on the surface of the nanowire changes. Since this can influence 

electronic behavior into the depth of the nanowire, a gating effect occurs that can be used 

in sensing. Figure 35 provides a representation of a nanowire configured as an FET. 

Figure 35. Nanowire in a field effect transistor (FET) configuration 
118 

Since they were discovered, silicone nanowires have primarily been investigated for 

sensing applications in biological systems (Cui et al. 2001). This is because the field 

effects on a nanowire functionalized with receptors are considerably larger with charged 

biological species than with ions. Nanowires have been viewed as one of 

nanotechnology's most promising current products for biomedical research (Hood et al. 

2004). Techniques for generating various types of important nanowires, nanorods, 

nanobelts, and nanotubes, synthetic strategies, research activities unique properties (e.g., 

thermal, mechanical, electronic, optoelectronic, optical, nonlinear optical, and field 

emission), and methods for assembling nanostructures into functional devices have been 

well reviewed (Xia et al. 2003). A comprehensive review of current research activities on 

chemical sensors based on nanotubes, nanorods, nanobelts, and nanowires, focusing on 

experimental principle, design of sensing devices, and sensing mechanism has recently 

been published (Huang and Choi 2007). Other sensing properties of silicon nanowires 

have been explored, such as gas sensing, where it has been observed that upon exposure 

to ammonia gas and water vapor, the electrical resistance of the HF-etched relative to 

non-etched silicon nanowires sample is found to dramatically decrease—even at room 

temperature (Zhou et al. 2003).

These materials have recently sparked considerable interest in nanoelectronics, in 

composite nanomaterials, and as conducting polymer nanowire sensors. Sensors and 

actuators assembled with conductive polymers nanowires are claimed to have superior 

responding characteristics to their conventional counterparts (Liu et al. 2004, 

Ramanathan et al. 2004, Alam et al. 2005). Conjugated polymers are organic 

macromolecules which consist at least of one backbone chain of alternating double and 

single bonds. This electronic structure allows a pi (π) orbital system, modifiable by 

intermolecular interactions and other functionalization, to extend along the entire length 

of the backbone, bestowing one-dimensional conductivity on the polymer. Sensors and 

sensor arrays based on conjugated polymers and carbon nanotubes have been 

investigated. The four basic electrical transduction modes—conductometry (monitoring 

the conductivity changes), potentiometric (monitoring the open circuit potential at zero 

current), amperometry (monitoring the change in current while the potential is kept 

constant), and voltammetric (monitoring the change in current while varying the applied 

potential)—have already been investigated (Dai et al. 2002). Heavy metal-ion sensing for 

drinking water analysis (Cu2+ and Ni2+ at parts per trillion range) have been demonstrated 

using a conducting polymer nanojunction array. Each nanojunction is formed by bridging 

a pair of nanoelectrodes separated with a small gap with electrodeposited, peptidemodified polyanilines and signal transduction sensing mechanism using the change in 

conductance due to polymer conformational changes induced by the metal-ion chelating 

peptide (Aguilar et al. 2005). Dielectrophoretically assembled poly (3,4-

ethylenedioxythiophene)/ poly (styrenesulfonate) have been investigated as sensors for 

acetone, methanol, and ethanol (Dai et al. 2002). 

Conducting polymer nanowire sensors have even been formed directly in place in 

microfluidics devices (Wang et al. 2006). Such an approach has a number of advantages, 

including: 
119 

1. the monomeric precursor polymerizes directly on the electrode surface, producing 

high-quality ohmic contacts; 

2. addressability is inherent to this method because nanowires can be grown across 

individual electrode junctions; 

3. the introduction and delivery of small amounts of precursor monomers and 

analytes are highly controllable and enable the rapid exchange of nanoliter-level 

solutions on the same; 

4. the turbulence-free environment within a microchannel helps the formation of 

well-defined conducting polymer nanowires during the electropolymerization 

process; and 

5. once the nanowires are grown, the entire device is ready for use, without the 

necessity of any postfabrication processing. Figure 36 provides a representation of 

an actual device. 

Figure 36. Conducting polymer nanowire sensor formed directly in microfluidics 

device showing (a) actual view of fabricated device, (b) optical micrograph of 

microfluidics device and (c) schematic with polyaniline and polypyrrole 
120 

Various types of nanowire have been studied for environmental applications other than 

sensors. For example, natural nanowires in electricigens (microorganisms able to 

completely oxidize organic compounds to carbon dioxide with the sole electron acceptor 

being an electrode) (Reguera et al. 2005, Reguera et al. 2006, Reguera et al. 2007); ZVI, 

iron-nickel, and iron-palladium nanowires have been studied as an alternative to iron 

nanoparticles in the remediation of chlorinated organics (Yoo et al. 2007); and 

regenerable gold nanowires have been studied as sensors for mercury (Keebaugh et al. 

2007). 

 

3.5.3 Summary of Environmental Potential 

 

Sensors based on nanowires are at an early stage of development. Their large surface 

area-to-volume ratio promises high sensitivity. Functionalization of the nanowire will 

allow a variety of species to be sensed. 

 

3.5.4 References 

Aguilar, A.D., E. S. Forzani, X. Li, N. Tao, L.A. Nagahara, I. Amlani, R. Tsui. 2005. 

Chemical sensors using peptide-functionalized conducting polymer nanojunction arrays. 

Applied Physics Letters. 87: 193108. 

Cui, Y., Q. Wei, H. Park, and C. M. Lieber. 2001. Science. 293: 1289. 

Dai, L., P. Soundarrajan, T. Kim. 2002. Sensors and sensor arrays based on conjugated 

polymers and carbon nanotubes. Pure Applied Chemistry. 74(9): 1753-1772. 

Hood, L., J.R. Heath, M.E. Phelps, B. Lin. 2004. Systems biology and new technologies 

enable predictive and preventative medicine. Science. 306: 640–643. 

Huang, X.J. and Y.-K. Choi. 2007. Chemical sensors based on nanostructured materials. 

Sensors and Actuators B: Chemical. 122 (2): 659-671. 

Keebaugh, S., W.J. Nam, S.J. Fonash. 2007. Manufacturable, Highly Responsive 

Nanowire Mercury Sensors. Presentation at Nanotech 2007 Conference, Santa Clara, CA, 

May 21, 20070 

Liu, H.Q., J. Kameola, D.A Czaplewski, H.G. Craighead. 2004. Polymeric nanowire 

chemical sensor. Nanotechnology Letters. 4: 671-675. 

Reguera, G., K. D. McCarthy, T. Mehta, J. S. Nicoll, M. T. Tuominen, D. R. Lovley. 

2005. Extracellular electron transfer via microbial nanowires. Nature. 435:1098-1101. 

Reguera, G., K. P. Nevin, J. S. Nicoll, S. F. Covalla, T. L. Woodard, D. R. Lovley. 2006. 

Biofilm and Nanowire Production Leads to Increased Current in Geobacter 

sulfurreducens Fuel Cells. Applied and Environmental Microbiology. 72(11): 7345-7348. 
121 

Reguera, G., R.B. Pollina, J.S. Nicoll, D.R. Lovley. 2007. Possible Nonconductive Role 

of Geobacter sulfurreducens Pilus Nanowires in Biofilm Formation. Journal of 

Bacteriology. 189: 2125-2127. 

Wang, J., Y. L. Bunimovich, G. Sui, S. Savvas, Y. Guo, J. R. Heath, H.-R. Tseng. 2006. 

Electrochemical Fabrication of Conducting Polymer Nanowires in an Integrated 

Microfluidic System. Chemical Communications. 3075-3077. 

Xia, Y., P. Yang, Y. Sun, Y. Wu, B. Mayers, B. Gates, Y. Yin, F. Kim, H. Yan. 2003. 

One-dimensional nanostructures: Synthesis, characterization, and applications. Advanced 

Materials. 15(5): 353-389. 

Yoo, B.-Y., S.C. Hernandez, B. Koo, Y. Rheem, N.V. Myung. 2007. Electrochemically 

fabricated zero-valent iron, iron-nickel, and iron-palladium nanowires for environmental 

remediation applications. Water Science and Technology. 55: 149-156. 

Zhou, X.T., J. Q. Hu, C. P. Li, D. D. D. Ma, C. S. Lee, S. T. Lee. 2003. Silicon nanowires 

as chemical sensors. Chemical Physics Letters. 369(1-2): 220-224. 
122 

3.6 Nanobelts and Nanorods 

3.6.1 Nanobelts 

Nanobelts are a class of nanostructure often viewed as a type of nanowire, usually made 

from semiconducting metal oxides (such as SnO2, ZnO, In2O3 or CdO, or selenides such 

as CdSe). Nanobelts form ribbon-like structures with widths of 30-300 nm, thicknesses of 

10-30 nm, and lengths in the millimeter range. They are chemically-pure and structurallyuniform single crystals, possessing rectangular cross sections, clean edges, and smooth 

surfaces. 

Figure 37. SnO2 nanobelts 

Much research has been conducted on the use of nanobelts as gas sensors. Current gas 

sensors typically use metal oxides (such as SnO2) as the sensing element, and operate by 

measuring changes in electrical conductance of the surface as it undergoes reduction or 

oxidation reactions with the gas. Though the exact mechanism is not fully understood, it 

appears that at high temperatures in the absence of oxygen, free electrons move easily 

through the oxide and across the boundaries between crystal grains. When oxygen is 

present, it is adsorbed on the oxide surfaces and at the grain boundaries, and (due to its 

affinity for electrons) it removes free electrons from the underlying material, creating an 

electron-depleted region and a potential barrier at the grain boundaries. This is 

manifested as an increase in resistance. In contrast, when a reducing gas is present, it too 

is adsorbed on the oxide surfaces and at the grain boundaries, where it can react with 

oxygen, and thus lower the oxygen-generated potential barrier. This is manifested as a 

reduction in resistance, allowing the sensor to act as a variable resistor dependent on gas 

concentration. 
123 

By virtue of their unique geometry, nanobelts have enormous surface areas per unit mass 

and most of the material is at the surface. When gases are adsorbed onto the nanobelt 

surface, the electron depletion or accumulation behavior becomes pronounced (as is the 

effect on the current flowing along the nanobelt) allowing them to act in a fashion similar 

to FETs. Further, their small size makes for greatly reduced power consumption over 

macroscale sensors. Research (Fields et al. 2006, Comini et al. 2002) has shown this 

behavior to be the basis for effective nanobelt gas sensors, and similar sensors have been 

made for nerve gas detection (Yu et al. 2005), ethanol sensing (Wan et al. 2004, Xue et 

al. 2005), and hydrogen sensing (Wang et al. 2005). 

Nanobelts possess essentially similar properties to nanowires; they can exhibit FET 

behavior and have functionalizable surfaces, thus making sensor development strategies 

for nanowires also available to nanobelts. 

3.6.2 Nanorods 

Nanorods are solid nanostructures morphologically similar to nanowires but with aspect 

ratios of approximately 3-to-5. They are formed from a variety of materials including 

metals, semiconducting oxides, diamonds (aggregated diamond nanorods produced from 

fullerenes are the hardest material so far discovered), and organic materials. Figure 38 

provides an image of ZnO nanorods grown from aqueous solution. 

Figure 38. ZnO nanorods grown in aqueous solution 

Nanorods are produced by a number of techniques, including: a vapor-liquid-solid 

approach; mechanical alloying; direct chemical synthesis using ligands for shape control; 
124 

plasma arc discharge; laser ablation; and catalytic decomposition (Ayala-Sistos et al. 

2005, He et al. 2002, Chopra et al. 1995, Goldberg et al. 1996, Goldberg et al. 2002, 

Hamilton et al. 1993). They are under considerable investigation for applications such as 

gas sensors; video displays; computer components; nanoelectronic and nanooptoelectronic components; MEMS devices; and solar energy conversion. One of the 

factors in their investigation is that both the size and shape can be controlled by use of 

additives during synthesis so that scaling—as well as basic properties—can be studied 

(Garcia and Semancik 2007), and flexibility is available for component integration 

(Benkstein et al. 2006). By functionalizing the nanorods, amphiphilic entities that can 

self-assemble and form convex curvature can be created—a capability of importance in 

nanoelectronic and biomedical applications (Park et al. 2004, Chen et al. 2007). Figure 39 

provides a graphic representation of a potential structure. 

Figure 39. Self-assembly of gold-polymer nanorods into a curved structure 

The particular morphology of nanorods also leads to properties that may have unusual, 

niche applications. For example, the light emitted from or scattered off of gold nanorods 

is strongly polarized along the rod length axis, an excellent property for an ideal 

orientation probe (Kou et al. 2006). 
125 

Nanorods have recently been subject of a newly demonstrated technique for the 

fabrication of nanostructures (Zhao et al. 2006). An ideal nanostructure fabrication 

method would have four desirable features: (1) the ability to control the size, aspect ratio, 

and shape of the nanostructures; (2) the ability to grow the desired nanostructure at low 

temperature and onto a particular substrate geometry (e.g., flat, cylindrical, or tapered); 

(3) the ability to fabricate metallic and dielectric nanostructures with multilayer 

structures; and (4) the ability to seamlessly integrate the fabrication process with other 

conventional microfabrication techniques. The following four general approaches have 

been employed to date: 

• nanolithography-based methods which use advanced lithographic techniques, 

such as electron beam lithography, x-ray lithography, and proximal probe 

lithography with deposition and plasma etching processes; 

• solution-based approaches which use very complicated, controlled wet chemical 

reactions to synthesize nanostructures and require a detailed understanding of the 

chemical reaction and crystal growth mechanisms; 

• vapor-based methods, such as the vapor-liquid-solid method used since the 1960s, 

which usually require higher temperatures and a specific catalyst for each 

structure; and 

• template-based methods using host nanoporous materials as forms. 

None of these fabrication methods are desirable features of an ideal method of fabricating 

nanostructured substrates, but Zhao et al. have investigated a novel nanostructure 

fabrication technique in the production of nanorods called glancing angle deposition 

(GLAD). GLAD is a physical vapor deposition technique in which the substrate is rotated 

in the polar and azimuthal directions by two stepper motors programmed by a computer. 

The experimental results have demonstrated that the GLAD technique offers several 

strategic advantages compared to other nanofabrication techniques—most particularly 

that the structures of the nanorods can be well designed by computer programming, a 

feature that cannot be achieved by any other fabrication technique. Control of this type, 

by whatever method is important since a novel, tapered form of nanorod, known as 

“nanorice”, has been shown to be the most sensitive surface plasmon resonance 

nanosensor yet devised (Wang et al. 2006, Srivastava and Lee 2006). 

Exploratory work on the use of nanorods for sensors is well underway. A biosensor for 

determination of heavy metals based on hydrothermally-grown ZnO nanorod/nanotube 

and metal-binding peptides has been presented. The ZnO acts as an FET and heavy metal 

binding with a peptide causes an electrical signal change, which can be measured and 

correlated to the concentration of heavy metals (Jia et al. 2007). A gold nanorod sensor 

for mercury is able to determine mercury in tap water samples at the parts-per-trillion 

level has also been developed. The selectivity and sensitivity result from the 

amalgamation of mercury and gold, and the entire sensing procedure takes less than 10 

minutes, with no sample separation and/or sample pre-concentration requirements. The 

only step prior to mercury determination consists of mixing the water sample with a gold 

nanorod solution in sodium borohydride. The limit of detection (6.6x10-13 g.L-1) shows 

excellent potential for monitoring ultra-low levels of mercury in water samples 
126 

(Hernandez et al. 2007). In work on the control of homogeneity in shape, size, and the 

organization of gold nanorods, the possibility of a copper sensor has been suggested. The 

basis of the idea is the strong dependence of surface plasmon resonance peaks on the size 

of gold nanorods, and the detection mechanism is based on the color change due to 

plasmon-plasmon interaction between adjacent gold nanorods. The gold nanorods were 

successfully functionalized with glutathione, and the addition of Cu2+ ions considerably 

improves the assembly, opening the possibility of making a copper sensor (Afshar 2007). 

3.6.3 References 

Afshar, R. 2007. Gold nanorods: Synthesis and self assembly. Master Project Micro- and 

Nanotechnology, University of Neuchatel, Switzerland, February 2007. 

Ayala-Sistos, J., G. Rosas, R. Esparza, R. Pérez. 2005. BN Nanorod Production Using 

Mechanical Alloying. Advances in Technology of Materials and Materials Processing. 

7(2): 175-180. 

Benkstein, K.D., C. J. Martinez, G. Li, D. C. Meier, C., B. Montgomery, S. Semancik. 

2006. Integration of Nanostructured Materials with MEMS Microhotplate Platforms to 

Enhance Chemical Sensor Performance. Journal of Nanoparticle Research. 8(6): 809-

822. 

Chen, T., Z. Zhang, S. C. Glotzer. 2007. A precise packing sequence for self-assembled 

convex structures. Proceedings of the National Academy of Sciences. 104: 717-722. 

Chopra, N. G., R. J. Luyken, K. Cherrey, V. H. Crespi, M. L. Cohen, S. G. Louis, A. 

Zettl. 1995. Boron Nitride Nanotubes. Science. 269: 966-967. 

Comini, E., G. Faglia, G. Sberveglieri, Z. Pan, Z.L. Wang. 2002. Stable and highly 

sensitive gas sensors based on semiconducting oxide nanobelts. Applied Physics Letters.

81:1869. 

Fields, L.L., J. P. Zheng, Y. Cheng, P. Xiong. 2006. Room-temperature low-power 

hydrogen sensor based on a single tin dioxide nanobelt. Applied Physics Letters. 88: 

263102. 

Garcia, S.P. and S. Semancik. 2007. Controlling the Morphology of Zinc Oxide 

Nanorods Crystallized from Aqueous Solutions: The Effect of Crystal Growth Modifiers 

on Aspect Ratio. Chemistry of Materials. 19(16), 4016–4022. 

Goldberg, D., Y. Bando, M. Eremets, K. Takemura, H. Yusa. 1996. Nanotubes in boron 

nitride laser heated at high pressure. Applied Physics Letters. 69: 2045-2047. 

Goldberg, D., Y. Bando, M. Mitote, K. Kurashima, T. Sato, N. Grobert, M. Reyes, H. 

Terrones, M. Terrones. 2002. Preparation of aligned multi-walled BN and B/C/N 

nanotubular arrays and their characterization using HRTEM, EELS and energy-filtered 

TEM. Physica. B. 323: 60-66. 
127 

Hamilton, E. J. M., S. E. Dolan, C. M. Mann, H. O. Colijn, C. A. MacDonald, S. G. 

Shore. 1993. Preparation of Amorphous Boron–Nitride and its Conversion to a 

Turbostratic Tubular Form. Science. 260:659-663. 

He, H., T.H. Wu, C.L. Hsin, K.M. Li, L.J. Chen, Y.L. Chueh, L. J. Chou, Z.L. Wang. 

2002. Beaklike SnO(2) Nanorods with Strong Photoluminescent and Field-Emission 

Properties. Small. 2(1), 116-120. 

Hernandez, F.E., M. Rexand and A.D. Campiglia. 2007. Pushing the Limits of Mercury 

Sensors with Gold Nanorods. Presentation at Nanotech 2007 Conference, Santa Clara, 

California, May 22, 2007. 

Jia, W., E.T. Reitz, Y. Lei. 2007. Biosensor for heavy metals using hydrothermally grown 

ZnO nanorods and metal binding peptides. Presentation at Nanotech 2007 Conference, 

Santa Clara, California, May 22, 2007. 

Kou, S.Z.X., C.-K. Tsung, M.H. Yeung, Q. Shi, G.D. Stucky, L. Sun, J. Wang, C. Yan. 

2006. Growth of Gold Nanorods and Bipyramids Using CTEAB Surfactant. Journal of 

Physical Chemistry B. 110: 16377-16383. 

Park, S., J.-H. Lim, S.-W. Chung, C.A. Mirkin. 2004. Self-Assembly of Mesoscopic 

Metal-Polymer Amphiphiles. Science. 303(5656): 348-351. 

Srivastava, D. and I. Lee. 2006. Nanorice and Nanospears from Polymer Nanospheres. 

Advanced Materials. 18: 2471-2475. 

Wan, Q., H. Li, Y. J. Chen, T. H. Wang, X. L. He, J. P. Li, C. L. Lin. 2004. Fabrication 

and ethanol sensing characteristics of ZnO nanowire gas sensors. Applied Physics Letters.

84: 3654-3656. 

Wang, H. T., B. S. Kang, F. Ren, L. C. Tien, P. W. Sadik, D. P. Norton, S. J. Pearton, J. 

Lin. 2005. Hydrogen-selective sensing at room temperature with ZnO nanorods; Applied 

Physics Letters. 86: 243503. 

Wang, H., D. W. Brandl, F. Le, P. Nordlander, N. J. Halas. 2006. Nanorice: a hybrid 

nanostructure. Nano Letters. 6: 827. 

Xue, X. Y., Y. J. Chen, Y. G. Wang, T. H. Wang. 2005. Synthesis and ethanol sensing 

properties of ZnSnO3 nanowires. Applied Physics Letters. 86: 233101. 

Yu, C., Qing Hao, S. Saha, L. Shi, Xiangyang Kong, Z. L. Wang. 2005. Integration of 

metal oxide nanobelts with microsystems for nerve agent detection; Applied Physics 

Letters. 86:063101. 
128 

4.0 Observations and Conclusions 

This document has synthesized a review of information on existing and potential 

applications of nano-enabled technologies for remediation and sensing of environmental 

pollutants, including radionuclides at contaminated sites. Since most environmental 

nanotechnologies are just emerging and cover a very broad spectrum of potential 

applications, the approach used in this document is to first present nanotechnologies that 

are currently being field tested followed by those that are still in the research and/or 

development stage. A wide range of promising nano-enabled technologies have been 

presented and discussed to the extent feasible. 

It is important to note that the majority of mature (tested and tried) nanotechnologies are 

dominant in the electronics and biomedical fields. Which nanotechnologies will actually 

migrate into environmental sensor (and possibly remediation) is challenging to determine 

at this time with significant accuracy, but comments were made in the document on 

extrapolation of nanotechnologies across scientific fields where appropriate. In addition 

to gathering the information presented here, the process of searching and examining the 

technical literature allowed some broad observations to be made. These collective 

findings may be summarized as follows: 

1. Nano-enabled technologies may be classified into two broad categories: 

remediation and sensing technologies. Remediation includes detecting, 

sequestration, and destruction of materials that constitute a threat to pubic health, 

welfare, and the environment. Sensing technologies, with enhanced sensors using 

nanomatrials, are used for detecting the presence of pollutants and could be used 

in monitoring releases for regulatory compliance. 

2. The classification in (1) above is most useful in presenting the overall state-ofthe-science if: a) a reasonable extrapolation is allowed from related behavior (e.g., 

it is accepted as reasonable that the success of a technology in the remediation of 

heavy metals signals the technology’s expected success for remediation of 

radionuclides), and b) the concept of environmental remediation is expanded to 

include radioactive waste management and radiological decontamination c) 

sensing of foreign substance or element may also serve as a prerequisite for 

furthering the development of environmental contaminant detection. 

3. In general, our understanding of nanotechnology risk is still developing. More 

information is needed on both the appropriate framework and on the basic 

information to be used within that framework. Additionally, the relationship 

between radionuclides and nanotechnology risk is even more elementary. A 

growing body of information and knowledge of the fate and transport of various 

nanomaterials should aid in the assessment of potential risks and mitigation of 

hazards to public health and the environment posed by nanotechnologies 

applications. 
129 

4. The physical and chemical properties (i.e., high surface area, high reactivity, easy 

dispersability, rapid diffusion, etc.) of nanomaterials provide the unique 

properties/capabilities for various environmental nanotech applications. The term 

“nanomaterial” is very broad and includes nanoparticles (based on overall size or 

gross dimensions), nanostructured materials (which may be microscale, 

mesoscale, or even macroscale particles, but still have nanoscale structural 

features, such as the channels in zeolites), and nanocomposite materials. 

5. A number of nano-enabled remediation technologies have either been field tested, 

trial demonstrated, or are close to and/or awaiting, full-scale implementation. 

These include ZVI nanoparticles (ZVI microparticles have already been used to 

remediate uranium contamination of ground water), zeolites (nanostructured 

materials that have been used in radioactive waste treatment for half a century and 

have been investigated for the remediation of radioactive cesium in soils, and are 

now available as nanoparticles), and a radiological decontamination gel 

(developed at ANL and employing a nanoparticulate radionuclide sorbent). As 

more nanotechnologies are applied in the field, performance data to include cost, 

operation and maintenance should be collected real-time to aid in further 

evaluation, and validating the sustainability of the environmental 

nanotechnologies applied to radionuclides. 

6. Based on analysis of the underlying technical and and scientific framework of a 

number of available nano-enabled remedial technologies, it is anticipated that 

nano-enabled technologies will have significant impact in the sensor development 

area. This is due to well-established fundamentals of sensor behavior that allow 

distinct advantages to be realized when the sensing events are measured at the 

molecular level. Despite the great potential for nano-enabled sensors, there are 

still some major hurdles to overcome in terms of reliable large volume production 

of nanoscale sensing elements, effective nanoscale manipulation, and integration 

of the nanoscale sensing elements with the external world. 

7. The electronics/biotechnological/biomedical driver for nano-enabled subsystem 

development has a two-fold benefit. It helps the cause of radionuclide site 

remediation by maintaining a development impetus, the benefit of which can be 

taken by those concerned with radionuclides. In doing so, this driver also puts 

limits on its own utility to radionuclides since biosensing has become the 

dominant paradigm and many developers are unaware of the needs of the 

environmental community. 

8. The issue of low visibility of environmental needs to the nano-enabled sensing 

community could easily be addressed by a straightforward communications effort, 

using avenues such as the Vision 2020 technology partnership or the MATCH 

Programme in the United Kingdom. 
130 

As can be ascertained from this report, nanotechnology is strongly supported by many 

federal agencies, though relatively little support by comparison is available for 

environmental applications. In addition, the market for environmental applications is 

perceived limited in compared to other fields such as biomedical and/or electronics to 

name a few. This may be a barrier to the rapid development and deployment of 

nanotechnologies for environmental applications. 

As discussed, there are many possible risk concerns associated with nanotechnology. 

Further, in the case of nanoparticle in situ applications there are risk concerns voiced in 

the literature and there is no regulatory guidance at this time. Risk concerns are a 

potential barrier to the acceptance and widespread deployment of nanoparticle based 

environmental technologies. Further, barriers may include the relatively limited market in 

environmental nanotechnologies. It seems most likely that nanotechnology-based sensors 

will be advanced further and will be more widely accepted, with nanotechnologies for 

remediation developing more gradually. 

As explained earlier, the purpose of this document is to provide an overview of the 

potential applications of nano-enabled technologies and subsystems to radionuclides in 

the environment, and to further an investigation of case studies to evaluate and validate 

the sustainability of various applications as they emerge. 
131 

Appendix A 

Acronyms 

AFM Atomic Force Microscopy 

AFO Amorphous Ferric Oxide 

ANL Argonne National Laboratory 

AlPOs Aluminophosphates 

ASTM American Standard Test Method 

CBEN Center for Biological and Environmental Nanotechnology 

DEFRA Department for Environment, Food, and Rural Affairs 

DMRB Dissimilatory Metal-Reducing Bacteria 

DND Detonation Nanodiamonds 

DoD U.S. Department of Defense 

DOE U.S. Department of Energy 

DSSR Double Skin Sheet Reactor 

EC European Commission 

EDA Ethylenediamine 

EDF Environmental Defense Fund 

EMSP Environmental Management Science Program 

EPA U.S. Environmental Protection Agency 

EU European Union 

EXAFS Extended X-Ray Absorption Fine Structure 

FDA Federal Drug Administration 

FET Field Effect Transistor 

GLAD Glancing Angle Deposition 

HOPO Hydroxypyridinone 

IAEA International Atomic Energy Agency 

IRGC International Risk Governance Council 

IR Infrared 

ITRC Interstate Technology & Regulatory Council 

ITRS International Technology Roadmap for Semiconductors 

ISO International Organization for Standardization 

IUPAC International Union of Pure and Applied Chemistry 

LOC Laboratory-on-a-Chip 

LSPR Localized Surface Plasmon Resonance 

MATCH Multidisciplinary Assessment of Technology Centre for Healthcare 

MCDA multi-criteria decision analysis 

MEMS Microelectromechanical Systems 

microTAS Micro-Total Analytical System 

NEAT-ORU Nanomaterials in the Environment, Agriculture, and Technology Organized Research 

 Unit 

NEIC National Enforcement Investigations Center 

NIH National Institutes of Health 

nm nanometer 

NMSP Nanoscale Materials Stewardship Program 

NNI National Nanotechnology Initiative 

NODE Nanowire-based One-Dimensional Electronics 

OAR/OTAQ Office of Air and Radiation/Office of Transportation and Air Quality 

OECA Office of Enforcement and Compliance Assurance 

OPP Office of Pesticide Programs 

OPPT Office of Pollution Prevention and Toxics 

ORD Office of Research and Development 

ORNL Oak Ridge National Laboratory 

OSWER Office of Solid Waste and Emergency Response 
132 

PCB Polychlorinated Biphenyls 

PCE Perchloroethylene 

PEBBLE Probe Encapsulated By Biologically Localized Embedding 

PEG Polyethylene Glycol 

PNNL Pacific Northwest National Laboratories 

PRB Permeable Reactive Barrier 

R&D Research and Development 

RCRA Resource Conservation and Recovery Act 

RDX Hexahydro-Trinitro-Triazine 

RO Reverse Osmosis 

RS/RAE Royal Society/Royal Academy of Engineering 

SAMMS Self-Assembled Monolayers on Mesoporous Supports 

SBIR Small Business Innovation Research 

SCENIHR Scientific Committee on Emerging and Newly Identified Health Risks 

SES Steward Environmental Solutions 

SETAC Society of Environmental Toxicology and Chemistry 

SPR Surface Plasmon Resonance 

STAR Science To Achieve Results 

STM Scanning Tunneling Microscope 

SWCNT Single-Walled Carbon Nanotubes 

TCA Trichloroethane 

TCE Trichloroethylene 

TDS Total Dissolved Solids 

TNT 2,4,6-Trinitrotoluene 

UNCD Ultrananocrystalline diamonds 

USNRC U.S. Nuclear Regulatory Commission 

VOC Volatile Organic Compound 

WSCP Water-Soluble Chelating Polymers 

ZVI Zero-Valent Iron 
133 

Appendix B 

Glossary 

Array: An arrangement of sensing elements in repeating or non-repeating units that are 

arranged for increased sensitivity or selectivity. 

Assembler: A general-purpose device for molecular manufacturing capable of guiding 

chemical reactions by positioning molecules. 

Atomic force microscope (AFM): An instrument able to image surfaces to molecular 

accuracy by mechanically probing their surface contours. A kind of proximal probe. 

Buckyball/C-60: see Fullerenes, of which “buckyballs” is a subset. The term 

“buckyball” refers only to the spherical fullerenes and is derived from the word 

“Buckminsterfullerene,” which is a geodesic dome/soccer ball-shaped C-60 molecule. C60 was the first buckyball to be discovered and remains the most common and easy to 

produce. 

Cantilever: A beam supported at one end and capable of defined bending and vibrational 

behavior. 

Catalyst: A substance, usually used in small amounts relative to the reactants, that 

modifies and increases the rate of a reaction without being consumed or changed in the 

process. 

Chemical Sensor: A device capable of providing quantitative or semi-quantitative 

information on a chemical species (or analyte) through calibration, and then brought into 

direct contact with the species in its environment. 

Conjugated Polymers: Organic macromolecules that consist at least of one backbone 

chain of alternating double and single bonds. 

Dendrimers: Artificially-engineered or manufactured molecules built up from branched 

unites called monomers. Technically, a dendrimer is a branched polymer, which is a large 

molecule comprised of many smaller ones linked together. 

Depth Filters: A type of filter in which the filter medium has a significant physical depth 

and the particles to be retained are captured throughout the depth of the filter. 

Disruptive Technology: Introduced in 2003, this term is used to describe a new 

technology that is significantly cheaper (or performs better) than a current technology. 

Electron beam lithography: Lithographic patterning using an electron beam, usually to 

induce a change in solubility in polymer films. The resulting patterns can be subsequently 

transferred to other metallic, semiconductor, or insulating films. 
134 

Electrospinning: A process for making nanofibers with diameters down to about 10 nm 

using an electrical charge to elongate and narrow fibers formed by an added melt. 

Enabling science and technologies: Areas of research relevant to a particular goal, such 

as nanotechnology. 

Engineered/manufactured nanomaterials: Nanosized materials that are purposefully 

made. These are in contrast to incidental and naturally-occurring nanosized materials. 

Engineering/manufacturing may be done through certain chemical and/or physical 

processes to create materials with specific properties. There are both "bottom-up" 

processes (such as self-assembly) that create nanoscale materials from atoms and 

molecules, as well as "top-down" processes (such as milling) that create nanoscale 

materials from their macro-scale counterparts. Nanoscale materials that have macro-scale 

counterparts frequently display different or enhanced properties compared to the macroscale form. 

Exploratory engineering: Design and analysis of systems that are theoretically possible 

but cannot be built yet, owing to limitations in available tools. 

Exposure assessment: The determination or estimation (qualitative or quantitative) of 

the magnitude, frequency, duration, route, and extent (number of people) of exposure to a 

chemical, material, or microorganism. 

Fullerenes: Pure carbon, cage-like molecules composed of at least 20 atoms of carbon. 

The word "fullerene" is derived from the word “Buckminsterfullerene,” which refers 

specifically to the C-60 molecule and is named after Buckminster Fuller, an architect who 

described and made famous the geodesic dome. C-60 and C-70 are the most common and 

easy to produce fullerenes. 

Green Rust: A class of Iron II/Iron III hydroxide compounds having a pyroaurite-type 

structure consisting of alternating positively charged hydroxide layers and hydrated anion 

layers. 

Incidental nanosized materials: Nanomaterials that are the byproducts of human 

activity, such as combustion, welding, or grinding. 

Lab-on-a-Chip (LOC): Also known as a micro-total-analytical system (microTAS), or 

microfluidics device, is a device that can integrate miniaturized laboratory functions, 

such as separation and analysis of components of a mixture, on a single microprocessor 

chip using extremely small fluid volumes on the order of nanoliters to picoliters. 

Limited assembler: Assembler capable of making only certain products; faster, more 

efficient, and less liable to abuse than a general-purpose assembler. 

Macroporous: Mesoporous materials with a pore diameter range greater than 50 nm. 
135 

Membrane filter: A filter that uses relatively thin material with a well-defined maximum 

pore size, with particle retaining effects taking place almost entirely at the surface. 

Mesoporous materials: Porous substances with pore diameters in the range of 2-50 nm. 

Microcantilever: A very small cantilever, the properties of which can be understood 

from basic engineering principles. 

Microfluidics: An interdisciplinary field dealing with the behavior and control of 

extremely small volumes of fluids and the design of systems that use these small 

volumes. 

Microporous: Mesoporous materials with a pore diameter range less than 2 nm. 

Molecular manufacturing: Manufacturing using molecular machinery, giving moleculeby-molecule control of products and by-products via positional chemical synthesis. 

Molecular nanotechnology: Thorough, inexpensive control of the structure of matter 

based on molecule-by-molecule control of products and byproducts; the products and 

processes of molecular manufacturing, including molecular machinery. 

Molecular recognition: A chemical term referring to processes in which molecules 

adhere in a highly specific way, forming a larger structure; an enabling technology for 

nanotechnology. 

Nano-: A prefix meaning one billionth (1/1,000,000,000). 

Nanobelts: A class of nanostructure often viewed as a type of nanowire, usually made 

from semiconducting metal oxides, such as SnO2, ZnO, In2O3 or CdO, or selenides such 

as CdSe. Nanobelts form ribbon-like structures with widths of 30-300 nm, thicknesses of 

10-30 nm, and lengths in the millimeter range. 

Nanoelectronics: Electronics on a nanometer scale, whether by current techniques or 

nanotechnology; includes both molecular electronic and nanoscale devices resembling 

today’s semiconductor devices. 

Nanomanufacturing: Same as molecular manufacturing. 

Nanometer: One billionth of a meter. 

Nanoparticle: Free standing nanosized material, consisting of between tens to thousands 

of atoms. 

Nanorods: Solid nanostructures morphologically similar to nanowires but with aspect 

ratios of about 3-to-5. They are formed from a variety of materials including metals, 
136 

semiconducting oxides, diamonds (aggregated diamond nanorods produced from 

fullerenes are the hardest material so far discovered), and organic materials. 

Nanoscale: Having dimensions measured in nanometers. 

Nanoscience: The interdisciplinary field of science devoted to the advancement of 

nanotechnology. 

Nanosensors: Chemical sensors possessing a nanoscale sensing element. 

Nanostructures: Structures at the nanoscale; that is, structures of an intermediate size 

between molecular and microscopic (micrometer-sized) structures. 

Nanotechnology: Research and technology development at the atomic, molecular or 

macromolecular levels, in the length scale of approximately 1-100 nm range; creating and 

using structures, devices, and systems that have novel properties and functions because of 

their small and/or intermediate size; and the ability to control or manipulate on the atomic 

scale. 

Nanotube: Tubular structure, carbon and non-carbon based, with dimensions in the 

nanometer regime. 

Nanowire: High aspect ratio structures with nanometer diameters that can be filled 

(nanorods) or hollow (nanotubes). 

PEBBLE (Probe Encapsulated by Biologically Localized Embedding): sub-micron 

sized optical sensors designed specifically for minimally invasive analyte monitoring in 

viable, single cells. 

Point-of-Care: Analytical testing performed outside the central pathology laboratory 

using a device or devices that can be easily transported to the vicinity of the patient. 

Quantum dot: A closely packed semiconductor crystal comprised of hundreds or 

thousands of atoms, and whose size is on the order of a few nanometers to a few hundred 

nanometers. Changing the size of quantum dots changes their optical properties. 

Scanning Tunneling Microscope (STM): An instrument able to image conducting 

surfaces to atomic accuracy; has been used to pin molecules to a surface. 

Sealed assembler lab: A general-purpose assembler system in a container permitting 

only energy and information to be exchanged with the environment. 

Self-Assembled Monolayers on Mesoporous Supports (SAMMS): Nanoporous 

ceramic materials that have been developed to remove contaminants from environmental 

media. 
137 

Self-assembly: The ability of objects to assemble themselves into an orderly structure. 

Routinely seen in living cells, this is a property that nanotechnology may extend to 

inanimate matter. 

Self-replication: The ability of an entity such as a living cell to make a copy of itself. 

Spectroscopy: The scientific study of the absorption, emission, or scattering of 

electromagnetic radiation by atoms, molecules, ions, solids, liquids, or gases. 

Sticking Coefficient: A standard term in surface chemistry and surface physics. It is the 

ratio of the number of adsorbate molecules that adsorb, or "stick", to a surface, to the total 

number of molecules that impinge upon that surface during the same period of time. A 

value of 1.00 means all impinging molecules stick, while a value of 0.00 means none 

stick. The concept is used in investigations of nanoparticle mobility in the subsurface. 

Superlattice: Nanomaterials composed of thin crystal layers. The properties (thickness, 

composition) of these layers repeat periodically. 

Surface Modified Membranes: Using technology to change the surface of the 

membrane, but not the underlying bulk material. 

Water-Soluble Chelating Polymers (WSCP): Polymers engineered to contain both 

highly elective chelating functionalities to bind with targeted metal ions, and solubilizing 

functionalities to allow the polymer to dissolve in water. 

Zeolite: A mineral with a pore size of less than 1 nm. 
138 

Appendix C

References for Figures 

Figure 2 accessed at http://www.nsf.gov/od/lpa/news/03/images/figure_1_zhang.jpg 

Figure 3 accessed at http://samms.pnl.gov/sammstech_summary.pdf 

Figure 4 accessed at http://sammsadsorbents.com/page/what-is-samms 

Figure 5 accessed at 

http://upload.wikimedia.org/wikipedia/commons/thumb/8/86/Filtration_diagram.sv

g/411px-Filtration_diagram.svg.png

Figure 6 and 7 accessed at http://www.kochmembrane.com/sep_nf.html 

Figure 8 accessed at 

http://www.sciencedirect.com/science?_ob=MiamiCaptionURL&_method=retrieve

&_udi=B6X1J-4J95TSYP&_image=fig3&_ba=3&_user=10&_coverDate=03%2F31%2F2006&_rdoc=1&_f

mt=full&_orig=search&_cdi=7244&view=c&_acct=C000050221&_version=1&_u

rlVersion=0&_userid=10&md5=78742dc3860626aacbd253add60720d7 

Figure 9 accessed at 

http://www.sciencedirect.com/science?_ob=MiamiCaptionURL&_method=retrieve

&_udi=B6X1J-4J95TSYP&_image=fig11&_ba=11&_user=10&_coverDate=03%2F31%2F2006&_rdoc=1

&_fmt=full&_orig=search&_cdi=7244&view=c&_acct=C000050221&_version=1

&_urlVersion=0&_userid=10&md5=941b7370b30b83fab17bc194218a4570 

Figure 10 accessed at http://www.foresight.org/conference2005/presentations/lee.pdf 

Figure 11 accessed at http://www.emembrane.com/tech.html 

Figure 12 accessed at http://en.wikipedia.org/wiki/Image:Zeolite-ZSM-5-3D-vdW.png 

Figure 13 accessed at http://upload.wikimedia.org/wikipedia/en/7/72/Nanodiamonds.jpg

Figure 14 accessed at http://www.nanonet.go.jp/english/mailmag/2007/091a.html

Figure 15 accessed at http://focus.aps.org/story/v11/st4 

Figure 16 accessed at http://upload.wikimedia.org/wikipedia/en/e/e8/Graphs.jpg

Figure 18 created by Dr. Eric Nuttall, University of New Mexico 

 

Figure 19 accessed at http://www.pnl.gov/news/release.asp?id=175 
139 

Figure 20 accessed at http://www.mesg.anl.gov/ 

Figure 21 accessed at http://www.whatsnextnetwork.com/technology/index.php/2006/07/ 

Figure 23 accessed at http://en.wikipedia.org/wiki/Nanomaterials 

Figure 24 accessed at 

http://upload.wikimedia.org/wikipedia/commons/c/c5/Fullerene_c540.png 

Figure 25 accessed at http://theor.jinr.ru/disorder/carbon.html

Figure 26 accessed at http://theor.jinr.ru/disorder/carbon.html

Figure 27 accessed at 

http://upload.wikimedia.org/wikipedia/commons/6/62/NanobudComputations70%2

5.jpg 

Figure 28 (L) accessed at http://www.physorg.com/news95082478.html 

Figure 28 (R) accessed at http://science.nasa.gov/headlines/y2006/16nov_locad.htm 

Figure 29 accessed at http://www.tastechip.com/labchip/nano_biochip.html

Figure 30 accessed at http://www.brunel.ac.uk/5118/esrg%20images/chip.jpg

Figure 31 accessed at http://www.answers.com/topic/atomic-force-microscope 

Figure 32 accessed at http://www.eng.umd.edu/media/pressreleases/pr072506_crabdetector.html

Figure 33 accessed at http://nano.cancer.gov/news_center/monthly_feature_2005_dec.asp 

Figure 34 accessed at http://picasaweb.google.com/lh/photo/0SEZilSwhpJgPv3-qpUfxg

Figure 35 accessed at http://www.defensetechbriefs.com/content/view/1023/34/

Figure 36 accessed at 

http://www.rsc.org/delivery/_ArticleLinking/DisplayHTMLArticleforfree.cfm?Jour

nalCode=CC&Year=2006&ManuscriptID=b604426c&Iss=29 

Figure 37 accessed at http://www.nanoscience.gatech.edu/zlwang/paper/HIpapers.html 

Figure 38 accessed at http://www.phy.bris.ac.uk/groups/electron_microscopy/index.html

Figure 39 accessed at http://nanotechnologytoday.blogspot.com/2007/11/gold-nanorodsshed-light-on-new.html
This page intentionally left blank. 

 
Printed on 100% recycled/recyclable paper EPA 402-R-09-002 | January 2009 | http://www.epa.gov/oar

with a minimum 50% post-consumer

fiber using vegetable-based ink.

PRESORTED STANDARD

POSTAGE & FEES PAID

EPA

PERMIT NO. G-35

Radiation Protection Division (6608J)

Washington, DC 20460

Official Business

Penalty for Private Use

$300