bluuebunny/crossref_metadata_2025_split huggingface dataset:
(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)
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.
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.
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
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.