bluuebunny/crossref_metadata_2025 huggingface dataset:
(Invited) Nanoporous Materials for Energy and Environmental Applications
Authors: Chen Mingwei
Published: February 2020

Bicontinuous nanoporous materials are emerging as a new class of functional materials because of a large surface area, high porosity and mechanical rigidity which traditional porous materials, such as metal foams, do not have. Coupled with excellent electric conductivity and rich surface chemistry, the nanoporous materials show great promises for energy and environment related applications. In this presentation I will introduce our recent works in the development of nanoporous metallic compounds by selective phase dissolution and nanoporous two-dimensional materials (graphene, MoS2, etc) by nanoporous metal based chemical vapor deposition. These novel nanoporous materials with tunable electronic structure and catalytic activities have been successfully employed as the catalytic electrodes for electrochemical and photoelectrochemical hydrogen productions, solar energy conversion, and Li-O2 batteries.
Metal-Organic Frameworks with Open Metal Sites for Sensing, Catalysis, and Energy Storage
Authors: Allendorf Mark D. , Stavila Vitalie , Talin Albert Alec , Ullman Andrew M. , Wang Timothy C.
Published: February 2020

Metal-Organic Frameworks (MOFs) are a class of coordination polymer in which metal ions and organic electron donors (“linkers”) assemble to form crystalline structures with stable nanoporosity. As a result of well-understood principles governing inorganic coordination chemistry and the rigidity and topology of the linkers, rational design principles have been established that allow MOFs to be designed and synthesized with properties selected for specific applications. Among the thousands of known MOFs, those with incomplete coordination shells around the metal ion (also known as open metal sites, or OMS) exhibit unique properties, including increased uptake of weakly interacting gases such as H2 and CH4, catalytic behavior resulting from substrate coordination to the OMS, and guest-dependent electrical conductivity that provides an avenue to electronic devices and sensors. This presentation will provide an introduction to MOFs and MOFs with OMS, then illustrate their possibilities using examples from our recent research: 1) catalytic cleavage of carbon-oxygen bonds found in lignin using activated H2; 2) colorimetric sensing; and 3) creation of electrically conducting MOFs using redox-active guest molecules such as TCNQ (7,7,8,8-tetracyanoquinodimethane). In each of these examples, guest molecules in the MOF pores interact directly with the OMS, resulting in bond polarization, modification of the electronic structure of the metal ion, and/or charge transfer between the metal ion and the guest. In the case of C-O bond cleavage, chemisorption of substrate ether molecules to Mg(II) ions in the IRMOF-74 series weakens the C-O bond. In addition, the MOF activates H2 molecules in solution with the substrate, as shown by isotope exchange experiments. Colorimetric sensing is enabled by guest binding to Cu(II) ions in the MOF known as HKUST-1, resulting in new charge-transfer transitions in the visible and near-UV. These perturbations of the electronic structure are relatively minor compared with the binding of TCNQ, a pi acid that bridges between two dimeric copper units in HKUST-1, creating a pathway for charge transport via a hopping mechanism. These results demonstrate that the novel features of MOFs with OMS provide the means to achieve completely new classes of catalysts and materials for chemical sensing and other electronic devices.
(Invited) Nanoporous Membranes By Self-Assembly of “Hairy” Nanoparticles
Authors: Zharov Ilya
Published: February 2020

Nanoporous membranes attract increasing attention due to their applications in molecular separations, biosensing, drug-delivery and catalysis. Most currently used membranes are formed by introducing pores into the bulk materials in a variety of irreversible processes. However, nanoporous membranes can be also prepared in a simple self-assembly process from nanoparticle building blocks, since particle solids contain interstitial voids which can function as interconnected three-dimensional nanopores. Membranes formed from nanoparticles using non-covalent interactions possess an additional advantage of reversible assembly which could prove useful for fabrication, processing, cleaning, reusing and would possess facile control over the membrane porosity and nanopore surface properties.

This talk will describe the preparation and characterization of durable, reversible nanoporous membranes with controlled thickness, area and pore size by self-assembly of silica nanoparticles grafted with polymer brushes ("hairy" nanoparticles, HNPs). The nanoparticles used to form the membranes are prepared by first modifying their surface with 2-bromoisobutyrylbromide (polymerization initiator) followed by surface-initiated atom transfer radical polymerization of a variety of methacrylate monomers. Nanoporous membranes are formed by casting HNPs from their suspensions in suitable solvents.

Three types of HNP membranes will be discussed: membranes made of HNPs grafted with polymer brushes carrying acidic and basic groups, membranes in which the grafted polymer brushes have neutral groups, and membranes grafted with negatively charged polymer brushes. Depending on the HNP type the membranes are stable in organic solvents but disassemble in water, or stable in water but disassemble in organic solvents. All types of HNP membranes are size-selective. When negatively charged groups are introduced to the side chains of the polymer brushes, the corresponding membranes a capable charge rejection. This talk will describe the different mechanisms of transport selectivity in nanoporous HNP membranes as well as the nanoparticle interactions in these materials that lead to their formation and stability.
Flexible Ceramic Membranes for Redox Flow Batteries
Authors: Newbloom Gregory M
Published: February 2020

Grid-scale power storage remains one of the largest challenges to wide-spread adoption of clean energy technologies with intermittent energy sources (e.g., solar, wind and tidal). Redox flow batteries (RFB) are an environmentally friendly and scalable technology with the potential to meet this need. However, ion exchange membranes that are crucial to battery performance are expensive, lack chemical stability in a strong oxidizing environment, and/or have poor ion selectivity which leads to electrolyte diffusion across the membrane and performance instability. These issues have limited commercial flow battery manufacturers to two options: 1) perfluorocarbon membranes - which are chemically robust and moderately ion selective but very expensive, or 2) separators - which are cheap but chemically degrade over time and have poor ion selectivity. In this paper, we discuss the design and scale-up of a novel, nanoporous ceramic flow battery membrane that is chemically robust, ion selective and inexpensive enough to reduce the total production cost of commercial flow batteries by > 15%.

In this work, we investigate the use of a primarily inorganic membrane created using sol-gel processing of silicates without calcination or sintering. Silica is an advantageous material for membranes because of its excellent chemical stability and extremely low cost. Furthermore, the gelation process can be utilized to tune the pore size for effective size exclusion of electrolytes (i.e., good ion selectivity). In this study, small angle x-ray scattering (SAXS) was utilized to characterize the membrane pore structure. Model fitting can be utilized to extract the porosity as well as pore shape, size and size distribution. By varying the gelation conditions, average pore radii were found to be in the range of 0.4 – 2 nm. This pore structure is nearly ideal for vanadium-based RFBs given that pores must be able to effectively transport protons (radius of 0.25 nm) but not vanadium ions (radius of 0.5 nm).

Proton conductivity and vanadium permeability were also determined and shown to be identical to an industry standard perfluorocarbon membrane (i.e., Nafion 212). Variation in membrane nanostructure was directly correlated to performance. Furthermore, on-going accelerated chemical oxidative stability testing shows no degradation for silica based membranes. These promising results highlight the commercial potential for a new flow battery membrane that is inexpensive, chemically robust and ion selective.
(Invited) Recent Advances in the Textural Characterization of Hierarchically Structured Nanoporous Materials
Authors: Thommes Matthias , Cychosz Katie
Published: February 2020

In recent years, major synthetic efforts have been focused on the introduction of hierarchical pore structures into many different materials such as zeolites, carbons, silicas, MOFs, hybrid layered and pillared structures. Nanoporous materials which consist of hierarchical pore networks with pore widths spanning the entire micro-mesopore range (i.e. up to 50 nm) allow one to overcome accessibility and diffusion limitations associated with classical microporous materials for catalysis and separations.

In this talk, recent developments in the structural characterization of these materials will be described. An accurate textural characterization is crucial not only within the discovery process of novel hierarchically ordered nanoporous materials but also contributes to advance their application in a variety of areas including heterogenous catalysis, separation, battery devices, drug delivery. Among a variety of techniques, gas adsorption is widely applied because it assesses a wide range of pore sizes, spanning the entire micro- and mesopore range. Within the last two decades major progress has been achieved in physical adsorption characterization also because of the development of advanced approaches based on statistical mechanics such as molecular simulation and density functional theory (DFT) [1]. This progress, coupled with the availability of high resolution experimental methodologies for the adsorption of various subcritical fluids (also allowing one to couple adsorption techniques with complimentary techniques such as small angle scattering), has led to major advances in the structural characterization of nanoporous materials. However, major challenges still exist concerning an in-depth characterization of complex pore networks. Application of characterization techniques to hierarchical materials has revealed new phenomena, such as cavitation processes during desorption, and led to significant refinement of these techniques [2]

[1] M. Thommes, K. Kaneko, A.V. Neimark, J.P. Olivier, F. Rodriguez Reinoso, J. Rouquerol and K.S.W Sing, (IUPAC Technical Report), Pure Appl. Chem. 87, 1051 (2015)

[2] K. A. Cychosz, R. Guillet-Nicolas, J. Garcia-Martinez, J., M. Thommes, M. Chem. Soc. Rev.
46, 389, (2017)
General Synthesis of Three-Dimensionally Ordered Macro-/Mesoporous Materials and Their Electrocatalytic Applications
Authors: Xu Lianbin , Sun Tingting , Chen Jianfeng
Published: February 2020

Three-dimensionally (3D) ordered macro-/mesoporous (3DOM/m) materials, which combine the advantages of high surface area of the mesopores, efficient mass transport within the macropores, and strong structural stability of the 3D interconnected porous frameworks, have shown remarkable performances in a wide range of applications. Herein, we demonstrate a novel dual-hard-templating technique as a general synthetic strategy for constructing the 3DOM/m materials by nanocasting mesoporous silica confined within the regular voids of a silica colloidal crystal (opal). Through this method, various materials, such as 3DOM/m Pt, Pd, Ni2P, carbon and N/P co-doped carbon (NPC), have been successfully synthesized. The as-prepared 3DOM/m Ni2P and NPC are demonstrated to exhibit outstanding electrocatalytic performance for the hydrogen evolution reaction (HER) and oxygen reduction reaction (ORR), respectively. The 3DOM/m Ni2P exhibits a low overpotential of 92 mV at 10 mA cm−2 and a small Tafel slope of 41 mV per decade, as well as a long-term durability for the HER in acidic medium. The 3DOM/m NPC exhibits comparable catalytic activity but higher durability in comparison with the commercial 20 wt% Pt/C catalyst for the ORR in alkaline medium. Details on the fabrication and characterization of these materials are presented including scanning electron microscopy, transmission electron microscopy, powder X-ray diffraction, nitrogen adsorption, X-ray photoelectron spectroscopy, and electrocatalytic activity studies.
Polyelectrolyte Modification of Nanoporous Membranes for Selective Ion Transport in Electrodialysis
Authors: Percival Stephen , Small Leo J. , Rempe Susan , Spoerke Erik D.
Published: February 2020

Nanoporous membranes can be used for electrodialysis-based water purification if the ionic selectivity and conductivity of the membrane can be increased. The electrodialysis process uses an applied DC electric field actively transport dissolved ions through the nanoporous membranes, concentrating the ions on one side of the membrane and purifying the water on the other side. Due to the large amount of electrical energy needed, electrodialysis is only used in a small number of water purification plants. One way to increase the efficiency of this process is to increase the ionic selectivity of the membranes. We describe here the use of inexpensive, commercially available polymer supports modified with polyelectrolyte surface chemistries. Specifically, we use a Layer-by-Layer (LbL) assembly to carefully modify nanopore surfaces with polyelectrolyte thin films. We explore how these thin films modify the surface charge influencing the ion selectivity and conductivity of these nanoporous membranes. We can further tailor the properties of the membranes through crosslinking to impact not only the chemical selectivity but also the chemical and mechanical stability of the polyelectrolyte surface modification. using various chemical crosslinking agents to increase not only the chemical selectivity of the membranes, but also their adhesion to the support membrane. We describe the preparation and characterization of these modified nanoporous membranes and evaluated the resulting ionic conductivity. Variations in the structure and composition of the starting nanoporous support membrane, polyelectrolyte deposition parameters and crosslinking chemistries are shown to controllably influence the ionic selectivity and conductivity of the nanoporous membranes as well as adhesion of the polyelectrolyte coating. Continued advances of these engineered nanoporous supports will enable the widespread use of electrodialysis as an economical water purification technology.

Sandia National Laboratories is a multi-mission laboratory managed and operated by National Technology and Engineering Solutions of Sandia, LLC., a wholly owned subsidiary of Honeywell International, Inc., for the U.S. Department of Energy’s National Nuclear Security Administration under contract DE-NA0003525.
Electrical Double Layer Capacitance of Ultra-Microporous Carbon Synthesized Using Zeolite Template
Authors: Lee Taekyoung , Ko Seung Hyeon , Ryoo Ryong
Published: February 2020

Electric double layer capacitor (EDLC) has gained much attention as a power source in electronic devices and hybrid electric vehicles, due to high power density, long cycle life, and long lifetime. Porous carbons have been extensively investigated as an electrode material for EDLC because of their high surface area wherein large amounts of electrolytes can be accumulated. Recently, an anomalous increase in the specific capacitance was observed for the carbon materials with pore diameters less than 1 nm. It was explained by the accumulation of desolvated electrolyte ions in the micropores. Furthermore, in an aqueous solution, it was reported that ultra-micropore of 0.5 nm was effective for high capacitance.

In this work, we investigated EDLC behavior of ultra-microporous carbon synthesized using ZSM-5 zeolite as a template. For the synthesis of the carbon, ZSM-5 zeolite was fully ion-exchanged with Ca2+ ion and acetylene was used as a carbon source. The embedded Ca2+ ions promoted the carbonization of acetylene at 500°C, leading to the pore-selective carbon deposition without external carbon layer. The resultant carbon reflected the morphology of the zeolite quite well. Furthermore, Ar sorption results showed that the carbon had ultra-micropores of 0.5 nm, corresponding to thickness of the zeolite pentasil layer. The electrochemical performances of the carbon were measured with a two-electrode cell in 6 M KOH. The cyclic voltammogram of the carbon had a quasi-rectangular shape, indicating capacitive behavior. In the galvanostatic charge/discharge experiment, the specific capacitance of the carbon was higher than that of commercial activated carbon, although the carbon has lower BET surface area. We attribute these results to the accumulation of desolvated electrolyte ions in the ultra-micro pores of 0.5 nm.
A Nano-Carbon Scaffold (NCS) Electrode for the Vanadium Redox Flow Battery
Authors: Li Jialang , Fofana Daouda , Li Xiaoan , El-Sawy Ehab , Birss Viola , Shakeri Hosseinabad Fatemeh , Maslovara Sladjana , Roberts Edward P.L.
Published: February 2020

In this study a template nano-carbon scaffold (NCS) electrode material is evaluated for use in the vanadium redox flow battery (VRB). Scanning electron microscopy (SEM) was used to characterize the morphology of the electrode materials. This material has an organized nanoporous structure and the pore size can be as small as 18nm. The electrochemical properties of the NCS materials were explored using cyclic voltammetry (CV). To investigate the performance of NCS as an electrode material, the NCS was attached to the surface of conventional carbon paper electrodes. The charge discharge performance of the VRB was determined using a flow through mode of operation. The performance of nano carbon scaffold (NCS) with different pore size and thickness was compared with a conventional heat-treated carbon paper. The results show that by using nano carbon scaffold (NCS-85-HT), the voltage efficiency increased from 77% to 94% at 10 mAcm-2. The energy efficiency also increased from 56% to 69% at 10 mAcm-2due to the increased voltage efficiency. The results indicate that the large surface area of the NCS, associated with its nano structure, lead to a reduction in overpotential of around 75%, and thus higher battery efficiencies. Cell performance under different current density was also explored and the improved efficiencies for NCS were maintained at all the current densities studied.
Investigation of Nanoporous Carbon Scaffold with Ordered Pore Structure As Microporous Layer for PEM Fuel Cells
Authors: Islam Muhammad Naoshad , Atwa Marwa , Li Xiaoan , Forouzandeh Farisa , Shrivastava Udit , Birss Viola , Karan Kunal
Published: February 2020

The microporous layer (MPL) is a key component of the membrane electrode assembly (MEA) of a polymer electrolyte membrane fuel cell (PEMFC). Historically, the MPL has been prepared by applying a slurry of carbon particles and Teflon onto the carbon paper. Together, the carbon paper with the MPL on it is known as the gas diffusion layer. The MPL fabricated by the aforementioned method results in a random pore structure varying both in pore size (ranging 20-200 nm) and wettability (hydrophobic and hydrophilic). Although the primary role of the MPL is thought to improve water management, delineation of the effect of pore size from wettability becomes difficult in a physically and chemically heterogenous porous structure of a conventional MPL.

Recently, the Birss group has developed nanoporous carbon scaffolds (NCS) with an inverse opal structure that has well-defined and tunable pore sizes. The wettability of the internal surface of the NCS films can also be altered by functionalization, from highly hydrophilic to hydrophobic. We have successfully integrated the NCS as an MPL in PEMFCs and evaluated its performance under low and high RH operations. The effect of pore size and wettability of NCS-based MPLs on the performance of PEMFCs will be presented in this talk.
(Invited) Nanoporous Materials for Fast and Reversible Electrochemical Energy Storage
Authors: Tolbert Sarah H
Published: February 2020

In this talk, we examine ways that solution processed nanostructured materials can be used to address both fundamental and practical issues relevant to next generation electrochemical energy storage. Materials with appropriate porous architectures can be synthesized using a range of solution phase methods, including polymer templating, nanoparticle assembly, and selective solution phase dealloying of mixed metal solid-state precursors. We begin with nanoporous materials for application in fast charging pseudocapacitors, with a goal of both defining the limits of pseudocapacitance in nanostructured materials and of establishing design rules for synthesizing highly capacitive materials. We find that in optimized nanoporous materials, the nanoscale structure and porosity can produce a very desirable combination of electrical connectivity, electrolyte access to the interior of the material, ample surface redox sites, and very short solid-state diffusion lengths for lithium ions, all of which facilitate fast charge and discharge. Perhaps more importantly, many nanoscale materials appear to show suppression of the intercalation induced phase transition that can cause kinetic limitations in bulk materials. Similar porous architectures can also be used to increase stability and cycle life in high capacity alloy-type anode materials that normal show significant strain related degradation. Using X-ray microscopy, we are able to directly image changes in pore structure upon cycling, so that materials and architectures can be optimized for stable cycling. Taken together, these results emphasize the key role played by nanoscale porosity in electrochemical energy storage materials.
(Invited) Nanoscale Chemistry and Electrochemistry with Porous Silicon Nanoparticles
Authors: Sailor M. J.
Published: February 2020

Prepared by electrochemical or chemical etch of crystalline silicon, porous silicon is an intrinsically strong reducing agent, enabling electroless deposition of noble metals via galvanic displacement. In addition to acting as an electron source, the oxidation of silicon generates water-soluble silicic acid as a chemical byproduct. This combination of electrochemistry and chemistry can be harnessed to form new, functional structures that with interesting applications in sensors, nanomedicine, and catalysis. A biological analog for these chemical and electrochemical processes can be found in cellular autophagy, where cellular components such as proteins and organelles are turned over to generate new cellular functions. The reducing ability of elemental silicon and the low solubility of silicate byproducts allow for inorganic autophagy in silicon nanostructures. For example, in the presence of silver or palladium ions, metal nanoparticles are formed by electroless deposition within a porous Si nanoparticle, generating composite nanoparticles with dimensions and properties controlled by the porous nanostructure. One approach to control the size of the resulting metallic nanoparticles is to use ammine complexes of the metal salt precursors. When the metal coordination complex is reduced, it releases free ammonia that locally dissolves the SiO2 reaction byproduct that would otherwise lead to heterogeneous metal deposition. The resulting materials can be used as catalysts, imaging probes or as in vivo antibacterial agents. Alternatively, dissolution of Si generates orthosilicic acid, which precipitates in the presence of calcium or magnesium ion to form a structural silicate shell that can be used to trap molecules or other nanostructures for therapeutic or analytic applications. This presentation will discuss the chemistry, the electrochemistry, and the photochemistry of nanostructured porous silicon, with emphasis on the self-destruction and reconstruction processes that can be harnessed for the above-mentioned applications.
Engineered Nanoporous Anodic Alumina Structures for the Development of Advanced Sensing and Drug Delivery Systems
Authors: Xifré-Pérez Elisabet , Ferré-Borrull Josep , Acosta Laura Karen , Pol Laura , Pallares Josep , Marsal Lluis F
Published: February 2020

Nanoporous anodic alumina (NAA) is a semiconductor material with interesting physical, mechanical, chemical and optical properties [1]. NAA is formed by the electrochemical etching of aluminum and presents a self-ordered hexagonal pore distribution with tunable pore diameters, pore lengths and interpore distances (figure 1) [2].

The high effective surface area of NAA (hundreds of m2/cm3) makes it a versatile and interesting platform for loading active agents like drugs or molecules as pores are used as reservoirs [3]. Based on this principle, we present here the use of NAA to develop advanced drug delivery systems and gated materials for biosensing applications.

The development of a new generation of local and selective drug delivery platforms with sustained release profiles is necessary to overcome the disadvantages of conventional treatments (generally oral or intravenous administrations) with considerable adverse effects [4]. The high effective surface area of NAA makes it an ideal material for drug delivery applications: the pores are nanocontainers with regular and controlled structural characteristics where active agents like drugs or molecules can be loaded [5]. Besides, the surface of NAA can be easily functionalized to be selective for specific molecules and covered with biodegradable, chemical, or pH responsive agents to trigger and regulate the release [6].

The pore geometry is one of the most important factors for the drug loading and for the release profile. Three-dimensional pore structures, with complex pore geometries and increasing surface area are promising morphologies for sustained drug release. However, their fabrication can be expensive and difficult. NAA, readily and cost-effectively fabricated by electrochemical anodization, permits obtaining elaborate and reproducible three dimensional pore geometries for sustained drug release platforms (figure 1) [7].

The biosensors we propose also follow the same concept of nanocontainer-pores introduced for the drug delivery systems. They consist of a NAA platform where the pores are loaded with a fluorophore and blocked by selected molecules that are able to recognize selectively a certain target analyte. The presence of the analyte unblocks the pores resulting in the selected release of the entrapped reporter. These gated biosensors based on NAA have high potential for the selective and sensitive detection of molecules that currently require complex and/or long processing. These nanostructured biosensors are very simple to prepare, easy to handle, reusable, and do not require trained personnel. We report here the use of these NAA biosensors for the selective detection of drugs and bacteria

Figure 1
Formation and Functional Features of Self-Ordered TiO2 Nanotube Arrays
Authors: Schmuki Patrik , Zhou Xuemei , Liu Ning , Altomare Marco
Published: February 2020

TiO2 nanomaterials have over the last 30 years attracted tremendous scientific and technological interest. Main research direction using TiO2 in functional applications are still the use in photocatalysis e.g. for the direct splitting of water into H2 and O2 to generate the potential fuel of the future, hydrogen, or the use in Grätzel type solar cells. In order to achieve a maximum turn-over rate (by creating a high surface area), usually nanoparticles are used either suspended or compacted to a photoelectrode. Over the past decades various 1D and highly defined TiO2 morphologies were explored for the replacement of nanoparticle networks and were found in many cases far superior to nanoparticles. Nanotubes or wires can be grown by hydrothermal or template methods, or even more elegantly, by self-organizing anodic oxidation. The latter is not limited to TiO2 but to a full range of other functional oxide structures on various metals and alloys can be formed. These advanced and doped morphologies can be grown on conductive substrates as ordered layers and therefore can be directly used as functional electrodes (e.g. photo-anodes). The presentation will focus on these highly ordered nanotube arrays of TiO2 and discuss most recent progress in synthesis, modification and applications.

Literature: (reviews):

- P. Roy, S. Berger, P. Schmuki, Angew. Chem. Int. Ed. (2011), 2904

- K. Lee, A. Mazare, P. Schmuki, CHEMICAL REVIEWS, 114 (2014) 9385
Morphological Control Effect of Hierarchical Heterostructure α-Fe2O3/TiO2 Nanotube for Photoelectrochemical Water Splitting
Authors: Han Hyungkyu
Published: February 2020

Large-band gap metal oxide TiO2 have suitable band positions for photoelectrochemical cells (PECs) for solar-driven water splitting, but uses only UV light region in the solar spectrum which represent only about 5 % of the energy. On the other hand, α-Fe2O3 with suitable bandgaps for efficient absorption in the solar spectrum require an external bias to drive hydrogen generation at the cathode due to the conduction band of α-Fe2O3 below the H2 evolution potential and have short carrier diffusion lengths. Synthesizing the metal oxide nanomaterials which have both suitable band position to drive reaction and visible light absorbed band gap is one of the major challenge in PECs for water splitting field. Hetero structure of α-Fe2O3 and TiO2 offer a potential solution to improve this problem. However, the inherent low electrical conductivity resulting in the high electron-hole pair recombination rate and short carrier diffusion length of α-Fe2O3 limit its practical use. Here we report a novel hierarchical heterostructure of α-Fe2O3 ultrathin nanoflakes branched on TiO2 nanotube strategy for PECs for water splitting. On the basis of the detailed experimental results and associated theoretical analysis, we demonstrate that suitable morphological control of α-Fe2O3 and TiO2 plays an important role in enhancing the photoelectrochemical water splitting performance.
A New Low Temperature Electrochemical Hydrocarbon and NOx Sensor
Authors: Sekhar Praveen K. , Aravamudhan Shyam , Khosla Ajit
Published: February 2020

In this article, a new investigation on a low temperature electrochemical hydrocarbon and NOx sensor is presented. Based on the mixed potential based sensing scheme, the sensor is constructed using platinum and metal oxide electrodes, along with Yttria-Stabilized Zirconia (YSZ)/Strontium Titanate (SrTiO3) thin film electrolyte. Unlike traditional mixed potential sensors which operate at higher temperatures (> 4000 C), this potentiometric sensor operates at 2000 C with selective hydrocarbon (HC) and NOx response in the open-circuit and biased mode respectively. The possible low temperature operation of the sensor is speculated primarily due to the enhanced oxygen ion conductivity of the electrolyte, which may be attributed to the space charge effect, epitaxial strain, and atomic reconstruction at the interface of YSZ/STO thin film. The response and recovery time for the NOx sensor are found to be 7 seconds and 8 seconds respectively. The sensor exhibited stable response even after 60 days of testing, with 9.4% decrease in HC response and a 1.9% decrease in NOx response.
Sensitivity Control of Dye-Doped Polymeric Fiber-Optic Strain Sensor Using Radiative Emission-Absorption Mechanism
Authors: Furukawa Rei , Kamimura So
Published: February 2020

Principle of a novel fiber-optic strain sensor using dye-doped polymer optical fiber (POF) was demonstrated in the earlier ECS meeting[1]. This time, we demonstrate the ability to tune the sensitivity of this sensor by varying the numerical aperture of the fiber. The sensor uses radiative emission-absorption mechanism and it is capable in sensing stress (strain) by simple viewing of the large-core cross section. Conventional well-known fiber-optic strain sensors such as BOTDR or FBG types require spectral analysis to determine the strain value. Our sensor does not require expensive equipment such as spectral analyzer or well-tuned light source that are required in conventional fiber-optic strain sensors.

A pair of luminescent organic dyes, Coumarin 540A and Rhodamine 6G, that functions as donor and acceptor of excitation energy were doped in core and cladding of the fiber, respectively. By taking this structure, stress applied to the fiber could be detected as an increase in cladding intensity. This happens because emission of core dye leaks to the cladding due to the deformation, and it excites the cladding dye[2].

POFs with three different NA were fabricated by varying the amount of high-refractive index dopant in the core[2]. Using the fabricated POF, change in near field pattern and output visible spectrum upon different fiber bending diameter were detected. 406 nm output pigtail laser was used in order to excite the donor dye efficiently. Pigtail end was coupled to the test fiber with direct contact to the core center of the test fiber in which no cladding excitation was expected. Fibers were stressed in various magnitudes by bending them in different loop diameters, namely, 1.5 cm, 3 cm, and 6 cm. Single loop was created in the middle point of the whole length. Relaxed condition, which the fiber was naturally straightened with no loop, was also investigated. Output beam from the test fiber was analyzed using Near Field Pattern measuring system (Hamamatsu C9664-01G02) and spectral analyzing system (JASCO MF-3500).

As a result, linear change in sensor sensitivity was observed as the NA increases. Therefore, it was suggested that sensitivity of the sensor is controllable by further optimization of the waveguide parameters. Therefore, the proposed results suggests a potential for an enhanced fiber-optic stress detection with simpler and inexpensive accessory components.

[1] Kamimura and Furukawa, 232nd ECS meeting.

[2] Kamimura and Furukawa,Appl. Phys. Lett. 111, 063301 (2017)
Acoustic Sensors Coated with a Metal-Organic Framework for Room Temperature Monitoring of Carbon Dioxide and Methane
Authors: Devkota Jagannath , Kim Ki-Joong , Culp Jeffrey , Ohodnicki Paul R , Greve David W
Published: February 2020

Greenhouse gases emissions such as carbon dioxide and methane which are generated from the processing and use of fossil fuels have created serious environmental concerns. The need to monitor the emissions of these gases in mobile and stationary point sources present novel challenges in sensor design. Surface acoustic SAW devices, which offer high sensitivity, low cost, wireless and passive options as well as tunable selectivity when coated with proper sensing materials, can be a potential platform for monitoring these gases. However, many coating materials including metal oxides and polymers are not suitable for developing room temperature gas sensors due to their poor interaction capacity (physisorption or chemisorption) with the gases. Recently, metal-organic frameworks (MOFs) have drawn a considerable attention in sensing applications for their high sorption capacity at ambient condition and functional tenability. Here, we present on the development of surface acoustic wave (SAW) carbon dioxide and methane sensors by applying the zeolitic imidazolate framework-8 (ZIF-8) MOF as the sensing layer.

The SAW delay lines with the nominal operating frequency of 436 MHz were custom fabricated on Y-Z LiNbO3 piezoelectric substrates and 9 MHz quartz crystal microbalance (QCM) resonators made of At-cut quartz and gold electrodes were purchased from INFICON. The transducers were coated with 200 nm thick ZIF-8 layer by simple solution-based dip coating method and exposed to various gases at room temperature in a N2 environment. Relative to pure N2, the sensors showed a good response to CO2 and CH4 while remaining neutral to CO and air. The resonance frequency of the QCM sensor decreased by 217 and 9.2 Hz and the phase of the SAW in the delay line changed by 0.72 and 0.04 radian for pure CO2 and CH4, respectively. The responses of the sensors varied linearly with the concentrations of either gas. From a linear fit, the sensitivities of the QCM sensor to CO2 and CH4 were evaluated to be 2.18 Hz/vol-% and 0.1 Hz/vol-%, respectively. Similarly, the SAW sensor showed a sensitivity of 0.39 deg/vol-% to CO2 while its response to various concentrations of CH4 is under study. Since ZIF-8 is a non-conducting material and its stiffness changes negligibly upon gas adsorption for thin film cases, the mass loading effect can be considered the dominant sensing mechanism for both sensors. When the coated films adsorbed the gas molecules, their mass density increased thereby inducing a decrease in acoustic velocity which was recorded in terms of frequency or phase change. Given that the SAW sensors can be operated in wireless and passive mode, the current study is of great importance in developing passive sensors for distant monitoring of greenhouse gases in the environment and at other emission sites.
Wireless Zero-Power Air Quality Electrochemical Sensor Card for Iot Applications
Authors: Stetter Joseph R , Peaslee David , Patel Vinay , Meulendyk Bennett J.
Published: February 2020

A new business card size very low cost wireless electrochemical sensor device for use with smartphones and connection to the IoT has been developed. The gas sensor platform uses amperometric gas sensors, AGS, herein demonstrated for CO but easily expanded to many other important airborne contaminants. The NFC based communication could revolutionize low cost personal monitoring of environmental air quality. The technology is based on a 2-electrode electrochemical gas sensor, and can be adapted to a 3-electrode configuration as well. The platform is adaptable to other electrochemically active gases including but not limited to formaldehyde, H2, H2S, alcohol, NO2, CL2, O3 or SO2.

The application enables NFC equipped mobile phones and devices to communicate wirelessly with the sensor on demand. The phone app NFC provides all the power necessary to read the signal from the sensor and communicate the data to the smartphone. In this configuration the sensor needs no warm-up or stabilization time and has no need for a battery or power supply. By tailoring the electro-chemistry of the sensor, a zero external bias can be used and still maintain an effective response to the target analyte. For instance, testing has been performed using composite printed Pt electrodes and an aqueous electrolyte, packaged in a small cell (roughly 15mm x 15mm x 3.8mm). Properties such as stability and linearity have been studied and will yield a device with years of service in indoor, outdoor and workplace environments. A lower detection limit of about 200 ppb CO has been achieved making ambient air quality monitoring possible as well as CO alarms. We envision that this platform will be useful for many types of AGSs with differing electrode and electrolyte configurations for other gases.

The sensor module’s electronics consist of a few passive components, an NFC communications chip with analog or digital inputs, and a low power instrumentation amplifier. With modern flexible electronics, and engineered antennae, the device can be reduced in size for embedding into just about anything. Including a printed battery enables the device to log in real time, and allows for a 3 electrode sensor configuration in a postage stamp size.

Combining techniques such as screen printing of electrodes and electronics, reel to reel manufacturing, and conformal packaging, the cost to produce a complete gas detector can be less than a dollar each! This new capability allows widespread use in studies from environmental air quality to personal health and asset protection.

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Optical Fiber-Based Corrosion Sensor for Health Monitoring of Oil and Gas Infrastructure
Authors: Wright Ruishu Feng , Lu Ping , Ziomek-Moroz Margaret , Ohodnicki Paul R
Published: February 2020

Corrosion is a great concern in the oil and gas industry as it affects the infrastructure in exploration, production, transportation, processing, and CO2 sequestration. The ability to monitor corrosion online before structure integrity is compromised can have a significant impact on preventing catastrophic events resulting from corrosion. High durability is required for the corrosion sensors in extreme service conditions such as high temperature high pressure during drilling, production, and refining. A recent concept for early corrosion on-set detection involves the use of proxy materials integrated with the optical fiber sensor platform which is relatively inert and immune to electromagnetic interference (EMI). The electrochemical behavior of the proxy material could provide insight into the conditions in which corrosion is expected to occur. The proxy material was deposited on the optical fiber and tested in CO2 containing 3.5%wt NaCl solution at 30 oC. The optical spectrum was measured to monitor the interaction between the proxy material and the environment. The optical spectrum calibrated with the electrochemical results in the same condition can quantify the corrosive environment. The electrochemical method and surface analysis were utilized to characterize the proxy material.
In Sickness and in Health
Authors: Chandra Shaneel , Chapman James , Cozzolino Daniel , Power Aoife , Roberts Jessica
Published: February 2020

In this talk, I will be sharing the recent successes of our laboratories in developing smart sensors to address industry challenges. Formed in 2017, our Agri-Chem group at CQUniversity brings the collective expertise of sensor chemists, antifouling experts, analytical chemists, near- and mid-infrared experts and livestock specialists towards analytical detection. We are able to design sensors for monitoring animal welfare at the farm level as well as throughout the supply chain. Similarly, we are interested in biosensing platforms for early detection of serious medical conditions, for example Parkinson’s disease. My talk will also include our interest in partnering with the Queensland Government and the Commonwealth of Australia in protecting of the world’s greatest living natural wonder – the Great Barrier Reef, using smart nutrient probes. The presentation will be of interest to analytical and electrochemists as well as early career researchers who are interested in smart sensing applications with a view to develop their research background in Australia.
A Wearable Electrochemical Impedance Spectroscopy Device for Detection of Glucose in Sweat Using Zinc Oxide Based Flexible Biosensors
Authors: Sankhala Devang , Muthukumar Sriram , Prasad Shalini
Published: February 2020

Label-free detection of biomarkers has been of significant interest lately which proves to be a powerful means for point-of-care diagnostics. A low-power, low form factor wearable device is proposed for combinatorial detection of glucose in sweat using electrochemical impedance spectroscopy (EIS) technique. The wearable EIS device consists of a sensing analog front end and low-volume ultrasensitive flexible zinc oxide biosensors. Monoclonal antibodies specific to glucose oxidase were immobilized on a thiolated zinc oxide sensing electrode surface resulting in the modulation of charge transfer within the electrical double layer (EDL). The non-faradaic EIS response of the biosensor was used to calibrate the analog front end's response using ratiometric digital Fourier transform (DFT). In this work, thiolated biosensors are dosed with glucose concentrations ranging from 5-200 mg/dL and detection is performed using the analog front end. Continuous dose testing was performed to demonstrate the stability of sensor over prolonged periods of operation for glucose concentrations within the physiologically relevant range reported in synthetic and human sweat buffers. In addition, combinatorial detection of glucose and cortisol is performed to mimic the overall physiological response in hyperglycemic condition reported in the previous literature and demonstrate the reliability of the sensing device.
Vitamin B6 Cofactor Conjugated hPEI-AgNCs for Fluorescent Sensing of Metal Ions and its Application in Cells Imaging
Authors: Bothra Shilpa , Sahoo Suban K.
Published: February 2020

Silver nanoclusters have been extensively used to construct fluorescent sensors for the detection of metal ions. Many synthetic strategies have been employed for development of these remarkable fluorescent materials by using different organic or biological templates such as proteins, peptides, polyelectrolyte, and DNAs. In the case of polyelectrolyte, polyethyleneimine (PEI) is a positively charged hyper-branched polyamine regarded as an ideal template to modify and stabilize nanoparticles based on several advantages: firstly, PEI contains primary, secondary and tertiary amine groups, which could efficiently chelate with metallic nucleus and stabilize these particles against flocculation by the strong columbic interaction due to the inherent high cationic density of the polymer.1 Considering the benefits of PEI-AgNCs, we have synthesized PEI-AgNCs using formaldehyde as the reducing agent and further bio-conjugated with the active form of vitamin B6 cofactor pyridoxal 5 -phosphate (PLP) to tune the sensing properties. Thus, the bio-conjugation of PLP with PEI-AgNCs (PLP_PEI-AgNCs) results in the formation of Schiff base that perceive significance complexation-induced turn-on fluorescent response in the presence of Zn2+ and Cd2+ with the detection limit down to 50.5 x 10-8 M for Zn2+ and 59.0 x 10-8 M for Cd2+, respectively. Also, low cost covalently anchored cellulose strips were prepared using the nano-assembly PLP_PEI-AgNCs for the easy on-site detection of Zn2+ and Cd2+. In addition, the nanoprobe was employed in live cell imaging for the detection of intracellular Zn2+ in live HeLa cells.2

References

1. Manoth, M.; Manzoor, K.; Patra, M.; Pandey, P.; Vadera, S.; Kumar, N., Dendrigraft polymer-based synthesis of silver nanoparticles showing bright blue fluorescence. Materials Research Bulletin
2009,
44 (3), 714-717.

Bothra, S.; Paira, P.; Kumar Sk, A.; Kumar, R.; Sahoo, S. K., Vitamin B6 Cofactor-Conjugated Polyethyleneimine-Passivated Silver Nanoclusters for Fluorescent Sensing of Zn2+and Cd2+ Using Chemically Modified Cellulose Strips. ChemistrySelect
2017,
2 (21), 6023-6029.

Figure 1