bluuebunny/crossref_metadata_2025 huggingface dataset:
First-Principles Molecular Dynamics Studies of Proton Transport in Hydrogen-Bonded Media
Authors: Tuckerman Mark E.
Published: February 2020

Proton transport in aqueous and non-aqueous hydrogen-bonded media has long been an area of intense study due to its fundamental importance in emerging energy technologies such as hydrogen fuel cells and in biological problems such as proton pumping.  Our understanding of proton transport phenomena is based on the concept structural diffusion of a topological defect in the hydrogen bond network generally attributed to C. J. T. von Grotthuss.  Within this picture, long-range proton transport is driven by specific structural rearrangements in the local hydrogen bonding environment, however, pinning down the specific microscopic mechanisms in different media remains an immense challenge that has an immediate impact on the problem of designing novel materials for enhancing the proton transport process.  In this talk, I will show how first-principles molecular dynamics has contributed to our understanding of proton transport phenomena in a variety of systems including aqueous acidic and basic solutions (in the latter, the relevant transport process is of hydroxide ions), aand phosphate based materials including pure phosphoric acid and its mixtures with heterocycles.  In phosphate based systems, the dielectric properties are also of immense interest, and I will discuss the calculation of these from first-principles molecular dynamics.  In general, it will be shown that proton transport in aqueous systems relies largely on local fluctuations in the hydrogen bond network while phosphate systems, by contrast, transport protons along extended, polarized chains in a manner much closer to the original picture suggested by von Grotthuss.  Such mechanistic studies can help inform the process of membrane design for electrochemical devices such as fuel cells.

Figure 1
(Invited) DAN Assisted Formation of Charge Transfer Complex from Highly Charged Fullerenes and Conjugated Polymer
Authors: Wang Hsing-Lin , Cotlet Mircea , Chengju Kuo , Park YoungIl , Liu Zhongwei , Tsai Hsinhan
Published: February 2020

Water-soluble, same charged, cationic conjugated poly(phenylenevinylene) (PPV) and cationic fullerenes were complexed with negatively charged single stranded DNA and double stranded DNA via electrostatic and pi-pi interactions. The photoinduced charge transfer complex (PPV/DNA/C60) has a charge transfer and separation efficiencies at least comparable to those observed from oppositely charged, cationic PPV and anionic fullerene. DNA serves as a template that straightens the PPV chain conformation which leads to an enhanced quantum yield. Meanwhile, DNA allows incorporation of C60 by overcoming the electrostatic repulsion between PPV and C60. While oppositely charge donor and acceptor molecules feature charge transfer in the form of static quenching, for DNA-assisted charge transfer complexes, the charge transfer proceeds as a combination of static and dynamic quenching for ssDNA and purely dynamic for dsDNA.
Increasing Energy Storage in Activated Carbon Based Ultra-Capacitors through Plasma Treatment
Authors: Muriel Marcelis L. , Narayanan Rajaram , Bandaru Prabhakar R
Published: February 2020

The relatively low cost, high surface area/mass ratio (>1000 m2/g), and ease of manufacture, of activated carbon (AC) makes it the prototypical material for electrochemical capacitor (EC) electrodes. However, the net obtainable capacitance is hampered by a space charge capacitance (Csc
), which adds in series with the expected double-layer capacitance (Cdl
).  We present a method to enhance the capacitance of AC electrodes based on plasma processing techniques previously used on few-layer graphene (FLG) and carbon nanotubes1, where a three-fold enhancement in the measured capacitance was obtained. We will indicate the development of a novel AC electrode that is of low pore size2, and which has been purposefully introduced with charged defects via Argon ion irradiation. Extensive characterization using electrochemical techniques such as cyclic voltammetry, impedance spectroscopy, as well as structural characterization through the use of Raman spectroscopy will be reported. Our work will show that the ion-irradiation would lead to a change (i) of the Cdl

through modulating the effective charge storage surface area, as well as through (ii) a decrease of the Csc

through the addition of charged states3. Additionally, we will probe the possible contribution to the net measured capacitance, due to the introduced charges, from a parallel pseudocapacitance, (Cp
), composed of Faradaic charge-transfer or redox reactions4.

References:

[1] Narayanan, R., Yamada, H., Karakaya, M., Podila, R., Rao, A.M., and Bandaru, P.R. 2014

[2] Chmiola, J., Yushin, G., Gogotsi, Y., Portet, C., Simon, P.,  and Taberna, P.L. Science 313, 1760 (2006).

[3] Hoefer, M.A., and Bandaru, P.R.  Journal of Applied Physics 108, 034308 (2010).

[4] Conway, B.E. J. Electrochem. Soc.
1991, 1539-1548.
Nanoporous-Carbon As an Intercalation Host Material to Enable Multivalent Ion Electrochemical Energy Storage
Authors: Siegal Michael P. , Yelton W. Graham , Schwarz Haiqing
Published: February 2020

We study the use of nanoporous-carbon (NPC) as an electrically conductive host material for Mg2+ intercalation.  Negligible progress for multivalent energy storage via intercalation into existing carbonaceous materials has been made due to insufficient interstitial/interplanar spacing within the crystallographic structures to host the larger sizes of partially-solvated multivalent ions.  However, NPC has high surface area with open and accessible porosity, controllable via mass density, which can minimize the diffusional resistance.  Here, we grow NPC directly on stainless-steel disks, which are used as anodes to fabricate coin cells with solid Mg cathodes and a Grinard-based electrolye.  NPC mass density is controlled during growth, ranging from 0.06 – 1.0 g/cm3, and correlates directly with electrochemical characterizations.  In particular, cyclic voltammetry (CV) scans for NPC with density ~ 0.5 g/cm3 are consistent with the reversible intercalation of Mg ions.  Higher density NPC yields capacitive behavior, most likely resulting from the smaller interplanar spacings between graphene sheet fragments and tighter domain boundaries; lower density NPC results in asymmetrical CV scans, consistent with possible structural degradation resulting from mass transport through such a soft carbon material.

Briefly, NPC grows via pulsed-laser deposition with controllable mass densities ranging from ~ 0.05 to 2.0 g/cm3.  The internal structure of NPC self-assembles during growth and consists of nano-fragments of aligned graphene sheet stacks with interplanar spacings expanded by as much as 55% compared to crystalline graphite.  Indeed, typical crystalline domain sizes are only 1 – 2 nm in length, as determined by high-resolution transmission electron microscopy; hence, NPC consists of randomly-oriented graphene nano-crystallites with expanded interplanar spacings, and with a plethora of grain boundaries to enable rapid diffusion of species into an entire volume.  Ionic intercalation into graphite is well known.  Reducing the mass density of NPC increases the interplanar spacings.  Therefore, the advantages of using NPC to study Mg2+intercalation include the tunability of the interplanar spacings and the ability to deposit it onto any substrate material without using binder materials, both increasing the fraction of available carbon surface atoms and simplifying the interpretation of measurements.  This suggests the potential to successfully develop NPC as an intercalation host for multivalent energy storage.

This work is supported by the Laboratory Directed Research and Development program at Sandia National Laboratories. Sandia National Laboratories is a multi-program laboratory managed and operated by Sandia Corporation, a wholly owned subsidiary of Lockheed Martin Corporation, for the U.S. Department of Energy's National Nuclear Security Administration under contract DE-AC04-94AL85000.
Biomass Based Carbon Nanospheres As Electrode Materials in Lithium Ion Batteries
Authors: Arie Arenst Andreas , Lee Joong-Kee
Published: February 2020

In the past decades, the development of nano- carbon materials with well-defined characteristics such as fullerenes, nanotubes and graphene have been a very active area of research. Carbon nanospheres (CNSs) is other class of nanostructured carbon materials, and have shown good prospects for application as alternative LIB anodes. CNSs possess some remarkable characteristics such as high specific capacity and good rate capability as anode materials in LIB. Those specific characteristics are attributed to a combination of several factors, including a short diffusion paths for Li+ ions; good porosity and high surface area. CNSs can be synthesized by various techniques which influence the characteristics of resulting carbons in terms of sphere size, size distribution, crystallinity and microstructure. The synthesis process of CNSs include the chemical vapor deposition, hydrothermal carbonization, laser ablation and polymerization –carbonization. Carbon based materials have been initially synthesized from petroleum-derived compounds. Because of the depletion of carbon deposits and very serious concerns on global climate change and environmental pollution, the use of renewable natural resources such as biomass for production of carbon materials has been intensively explored in recent years. In this work, the synthesis of carbon nano-spheres onto the surface of activated carbon support was carried out by thermal assisted catalytic pyrolysis technique and utilizing palm oil as renewable and eco-friendly carbon source. The structure and morphology of the resulting nano carbons are examined with X-ray powder diffraction (XRD) and transmission electron microscopy (TEM). Cyclic voltammetry (CV) and cyclic test of the carbon product as an anode material for lithium ion batteries are also investigated. From TEM observations, it can be shown that CNSs has turbostratic structure in the presence of  Fe-metal catalyst. The CNSs have a stable cycle performance up to 100 cycles at a constant current density of 100 mA/g, showing its potential as an anode material in lithium-ion batteries.
(Invited) Mechanistic Studies of the Oxygen Reduction Reaction Electrocatalyzed By N-Doped Graphitic Carbon Materials
Authors: Li Liang-shi , Li Qiqi , Noffke Benjamin , Raghavachari Krishnan
Published: February 2020

The oxygen reduction reaction (ORR) is a crucial step in biological and industrial energy production. To directly convert fuels to electricity in devices such as fuel cells, electrocatalysts alternative to Pt or Pt alloys have been actively sought after, especially those with high performance, high endurance, and low cost. And for this reason N-doped graphitic carbon materials including carbon black, activated carbon, graphite, nanotubes, graphene, etc. have been intensively studied. Despite the recent progress, mechanistic studies of these materials are particularly difficult due to the inhomogeneity and complexity of the catalysts available. Consequently, our understanding has been mainly empirical, and improvements of the catalysts are primarily based on trial and error.

Herein we present our recent studies on well-defined, N-doped graphene nanostructures for the electrocatalyzed ORR. By combining experimental and theoretical work, we show that a two-electron reduction of the carbon is a key step in activating the oxygen. We also show that the dielectric environment of the catalysts play an important role in dictating the selectivity of the reaction.
Fe and N Functionalized-Ordered Mesoporous Carbon with Different Morphologies: Role of Fe on Surface Properties and Electrocatalytic Activity
Authors: Yang Dea-Soo , Song Min Young , Bae Eunjin , Yu Jong-Sung
Published: February 2020

Because of their high energy conversion efficiency, low pollution, low operating temperature, high power density, and wide range of applications, fuel cells have received a plethora of attention. Oxygen reduction reaction (ORR) takes place usually on Pt loaded on different carbon supports, but their large-scale commercial application has been precluded mainly by the high cost of the requisite noble metal. To overcome all the drawbacks of Pt or Pt-based catalysts, various efforts have been devoted to find its proper substitute. Heteroatom-doped carbon catalysts, due to their high stability, excellent electrocatalytic performance, and economic viability over costly Pt-based catalysts are being pioneered as a suitable alternative.

Although heteroatom-doped porous carbon materials have evolved as one of best possible solutions in this regard, the probable synergy of heteroatom doping and textural properties has not been well investigated yet in details. In this work, a detailed investigation is carried out on Fe and N-functionalized ordered mesoporous carbon (FeN-OMC) as electrocatalyst ORR in both alkaline and acidic media. The FeN-OMCs with different morphology are synthesized by pyrolysis of iron phthalocyanine-infiltrated corresponding SBA-15 silica templates. The as-synthesized FeN-OMC materials show excellent electrocatalytic ORR activity with nearly four electron transfer process. While the activity in alkaline media is nearly equal to or better than commercial Pt catalyst in terms of onset potential and diffusion-limited current density, it closely follows in acidic media, which is a tremendous achievement for non-precious metal catalysts developed till date. The most interesting observation is that not only heteroatom, but textural properties also affect catalytic activity profoundly. The physical presence of Fe species may be necessary in the synthesis of active heteroatom-doped carbon for high ORR activity, but may be not necessary any more for the as-prepared doped carbon to play as electrocatalyst for ORR.  Despite of being prepared with similar Fe and N content, the catalytic ability of FeN-OMC materials is gradually increased with decrease in mesopore channel length with maximum activity in thin platelet FeN-OMC. These observations demonstrate that structural morphology in addition to heteroatom and other textural properties, has significant synergistic influence on ORR catalysis in heteroatom-doped carbon materials.
Microwave-Assisted Solvothermal Synthesis of Pd-MnO2 Hybrid at Onion-like Carbons: Electrocatalytic Oxidation of Alcohols in Alkaline Media
Authors: Ejikeme Paul M. , Makgopa Katlego , Raju Kumar , Ozoemena Kenneth I.
Published: February 2020

The use of less toxic glycerol, (a non-flammable, volatile, and little-valued residue of biodiesel production), ethanol as well as ethylene glycol (EG) as fuel may be an interesting alternatives to methanol for Direct Alcohol Fuel Cell (DAFC) technology. The volumetric energy densities of glycerol, ethanol and EG are 5.80, 6.31 and 5.97 kW h L-1 compared to 5.81 kW h L-1for methanol makes them good fuel cell candidates [1-2]. The secret to the efficient electrocatalysis of alcohols is the use of efficient nanocatalyst. Palladium-based catalysts have emerged as the most viable electrocatalysts for alcohol in alkaline electrolytes. To harness the great catalytic potential offered by Pd, and to reduce cost, Pd-based alloys supported on different carbon supports are constantly used in direct alcohol fuel cells (DAFCs).

In this work, palladium-manganese oxide nanoparticles supported on carbon nano onions (Pd-MnO2/OLC) were synthesized using the microwave-assisted solvothermal technique.  Palladium-manganese oxide nanoparticles supported on Vulcan carbon (Pd@MnO2/XC–72) were also synthesized using the same technique for comparison. The catalysts were characterized using XRD, XPS, FESEM and HRTEM techniques. Electroxidation of the alcohols was performed in 0.5 M alcohol / 0.5 M KOH via cyclic and linear sweep voltammetry, chronoamperometric and elelctrochemical impedance spectroscopy.

Results obtained show that the catalyst supported on OLC exhibited the highest current density and least charge transfer resistance relative to the catalyst supported on XC–72. Pd-MnO2/OLC gave the best result amongst the catalyst synthesized with  respect to the current density, and electrochemical stability as well as exhibited the least charge transfer resistance in all the alcohols studied. For instance, the onset oxidation potential and current density of the glycerol oxidation process were -0.5386 V and 5.58mAcm-2, respectively. The implications of these results relative to methanol oxidation using the best catalyst system synthesized are discussed.

References

1. L.M. Palma, T.S. Almeida, A. R. de Andrade, ECS Trans. 2013 58(1): 651-661.

2. X. Zhang, P.K. Shen, Int. J. Hydrogen Energy 2013, 38, 2257-2262
Engineering Carbon Nanotubes As Oxygen Reduction Catalysts for Solid Acid Fuel Cells
Authors: Evoen Vanessa , Tavassol Hadi , Haile Sossina M
Published: February 2020

We report on the effect of the chemistry of multi-walled carbon nanotubes (CNTs) on the oxygen reduction reaction (ORR) in solid acid fuel cells (SAFCs) based on the proton conducting electrolyte cesium di-hydrogen phosphate (CDP). CDP undergoes a super-protonic phase transition at ~2300C (10-6 S/cm2-10-2 S/cm2), under humidified gas atmosphere, making it a suitable fuel cell electrolyte. Due to the high cost of using platinum as the state of the art oxygen reduction reaction (ORR) catalyst, significant effort has been devoted to developing non-precious catalysts.

In this work we explore the suitability of functionalized carbon nanotubes as ORR catalysts. Composite electrodes of fine micron-sized CDP particles and CNTs were prepared by mechanical milling and applied to either side of a dense membrane of CDP, in turn, placed between carbon paper current collectors. The CNTs were acquiring commercially and included both hollow (standard) and bamboo CNTs. In both cases, in addition to non-functionalized forms of the CNTs, both amine-functionalized and acid-functionalized analogs were evaluated. Electrochemical activity was measured by A.C. impedance spectroscopy under humidified oxygen (pH20 of 0.4 atm) at 2400C. 

Of the non-functionalized CNTs, the bamboo structure was found to have a higher activity than the hollow structure, with an area specific electrode resistance of 1700 ohm cm2 vs 3500 ohms cm2. Functionalization of the CNTs led to orders of magnitude increase in the ORR activity. In particular, the electrode resistance values dropped to ~350 ohms cm2 for the amine functionalized CNTs and ~40 ohms cm2 for the carboxylic acid functionalized hollow CNTs. Scanning electron microscopy (SEM) and Fourier transform infrared spectroscopy (FTIR) of the electrodes showed a relationship between the chemistry of the CNTs and the degree of mixing in the CNT/CDP composite, which may contribute to the differences in electrochemical behavior.
In Vivo Glucose Measurement Using Fine Needle Type Amperometric Glucose Sensor
Authors: Yasuzawa Mikito , Edagawa Kazuaki
Published: February 2020

Fine needle type glucose sensors having outer membrane layers of heparin and urokinase were prepared.   Glucose sensor properties were evaluated by in vitro measurement in phosphate buffer solution and horse serum, and in vivo measurement using the veins of rabbit. Glucose sensors were implanted using cannula and the blood glucose levels were influenced by the injection of glucose and insulin. Definite glucose was hardly observed at the days of implantation, while clear response was obtained after several days. This may due to the recovery from the damage of blood vessel received on the process of sensor implantation. Good correlation between in vitro blood glucose levels was obtained at especially low glucose level.  Clear glucose sensor response was obtained even after 10 days of implantation. The formation on thrombus was not observed on the surface of sensor implanted for 10 days.  This indicate that the glucose sensor with outer membrane of heparin and urokinase have excellent biocompatibility.

Figure 1
(Plenary) High Efficiency Coupling of Chemical Sensing to Chemical Treatment in Low-Dimensional Nanofluidic Structures
Authors: Xu Wei , Grismer Dane A. , Zaino Lawrence P. , Ma Chaoxiong , Foster Erick , Bohn Paul W.
Published: February 2020

We are interested in the design and construction of nanostructured architectures that couple molecular transport (analyte/reagent delivery), chemical sensing (optical or electrochemical) and subsequent chemical processing withinin the same physical construct.  The ultimate goal of these experiments is to produce chemical reagents in situ and consume them directly at a proximal reaction site, all within the confined geometry of a low-dimensional nanostructure, so that chemical transformations may be realized with optimal efficiency.  To realize this goal we are developing sensing strategies that efficiently match electron transfer and spectroscopic probing to low-dimensional, i.e. zero- and one-dimensional nanostructures. In one example, we are studying the tight coupling of electrokinetic nanofluidics to electron transport for high efficiency in situ reagent generation.  Solvent electrolysis at an upstream can be used to generate H2 or O2 for downstream catalytic reduction or oxidation reactions.  Chronocoulomtery is performed simultaneously with fluorescence imaging in order to follow the reagent generation quantitatively, then model proton-coupled electron transfer reactions can be used down stream to follow the spatial distribution of reagent through the co-generated OH- or H+.  Because transport and electron transfer are intimately coupled, high efficiency conversions are achieved. The extremely small Peclet numbers characteristic of nanofluidic flow mean that the efficiency of electrochemical treatment is improved to near 100% efficiency in nanofluidic architectures compared to diffusion-limited efficiencies of 5-10% in microfluidic structures.
Magnetoelastic Biosensors for Real-Time, Wireless Pathogen Detection on Surfaces
Authors: Chai Yating , Horikawa Shin , Hu JiaJia , Chin Bryan A
Published: February 2020

Recent outbreaks of Ebola in the United States have brought to the public’s attention the transfer of disease by contact with virus- and bacteria-contaminated surfaces ranging from hospital counters to door knobs to airplane seats. The need for a real-time, on-site technique by which pathogen-contaminated surfaces can be identified is immediate and real. Standard microbiological detection techniques, including enzyme-linked immunosorbent assay (ELSA), polymerase chain reaction (PCR) and plate count, are time-consuming and manpower-intensive. This paper describes research into wireless magnetoelastic (ME) biosensors combined with a surface-scanning coil that can be used to detect both viral and bacterial contamination of surfaces. This detection method takes less than 10 minutes and eliminates time-consuming sample preparation such as enrichment. This paper investigates the use of wireless ME biosensors for the surface-scanning detection of pathogens on surfaces. The ME biosensor consists of an ME resonator as the sensor platform and E2 phage as the bio-recognition element. The E2 phage is genetically engineered to specifically bind with Salmonella Typhimurium. The ME biosensor is actuated into mechanical resonance by an externally applied magnetic field. A microfabricated planar coil was used to measure the resonant frequency of multiple ME biosensors in real time. When this phage-coated ME biosensor comes into contact with Salmonella cells, the bacterial cells are captured and bound to the biosensor’s surface by the phage. The bound bacterial cells then cause the mass of the ME biosensor to increase, resulting in a decrease in the resonant frequency. The change of the resonant frequency is known to be directly proportional to the additional mass of the bacteria attached to the biosensor surface. As a model study, multiple E2 phage-coated biosensors (measurement sensors) were placed on surfaces spiked with Salmonella Typhimurium with various concentrations. Control sensors without phage were also used to compensate for environmental effects and non-specific binding. The limit of detection and repeatability of testing were found to be comparable to standard real-time PCR. In this manner, in-situ, continuous, real-time monitoring of pathogenic surface contamination can be performed on any surfaces.
Development of Biofilm-Based Electrocatalytic Materials for Biosensing and Bioenergetics
Authors: Kulesza Pawel J
Published: February 2020

Biofilms, are polymeric aggregates of microorganisms, in which cells adhere to each other on the electrode surfaces. Such systems are characterized by extracellular electron transfers involving c-type cytochromes (heme-containing proteins). Biofilms can be grown on inert carbon electrode substrates tend to exhibit electrocatalytic properties towards oxygen and hydrogen peroxide reductions in neutral media. The processes have been found to be further enhanced by introduction of multi-walled carbon nanotubes (MCNTs) that are modified with ultra-thin layers of organic (e.g. 4-(pyrrole-l-yl) benzoic acid. We expect here attractive electrostatic interactions between carboxyl-group containing anionic adsorbates and positively charged domains of the biofilm with c-type cytochrome enzymatic sites. Coexistence of the above components leads to synergistic effect that is evident from positive shift of the oxygen reduction voltammetric potentials and significant increase of voltammetric currents. Most likely, the reduction of oxygen has been initiated at the molecular (e.g. intentionally added cobalt porphyrin redox centers), whereas the undesirable hydrogen peroxide intermediate are further decomposed at the cytochrome sites.

            An additional subject of interest is the process of carbon dioxide (CO2) reduction. There has been a growing interest in catalytic systems capable of efficient conversion of carbon dioxide into fuels. One of the promising electrocatalytic materials exhibiting high activity in this process is a macromolecular complex of palladium (II) with Schiff-base-ligands. Reduction of carbon dioxide may lead to carbon-based fuels and its derivatives.

                Fabrication of the biofilm based matrices for anodic reactions has also been considered.  To facilitate electron transfers between the electrode surface and the redox protein centers, the concept of codeposition of multi-walled carbon nanotubes within the bioelectrocatalytic film has also been pursued here. First, carbon nanotubes are modified with ultra-thin layers of tetrathiafulvalene (TTF) or poly(dimethyldiallylammonium chloride) (PDDA) mediators. Their presence is expected to facilitate flow of electrons from the enzyme (e.g. glucose oxidase) active sites through biofilm to the electrode surface. Combination of intentionally derivatized carbon nanotubes with biofilm matrtices and the appropriate enzymes seems to produce biocatalytic systems capable of effective oxidation and sensing of glucose or ethanol in the neutral buffered solution.

Collaboration with W. Lotowska, E. Szaniawska, E. Seta, M. Gierwatowska, B. Kowalewska and I.A. Rutkowska (from Faculty of Chemistry) as well as A. Raczkowska and K. Brzostek (from Faculty of Biology) is acknowledged.
Peroxynitrite Sensing: From Graphene-Based Platforms to Modified Boron-Doped Diamond Electrodes
Authors: Bayachou Mekki , Kalil Haitham
Published: February 2020

Peroxynitrite (PON) is a major cytotoxic agent, implicated in a host of pathophysiological conditions. In biological systems, peroxynitrite is the primary product of the reaction of superoxide ion and nitric oxide, and has been lately at the forefront of investigations dealing with nitroxidative stress. One major challenge in the analytical determination of peroxynitrite under physiologic conditions is its short half-life and its fast reactivity with many cellular targets.  Spectroscopic and other detection methods for peroxynitrite have been proposed but face the problem of real-time quantification and particularly when localized measurements are needed.  We have shown that catalyzed electrochemical detection of peroxynitrite is a simpler and more convenient technique. In the past, we described the use of polymerized hemin (iron protoporphyrin IX) and other porphyrins on graphite electrodes as platforms for amperometric measurement of peroxynitrite both in still solutions and under flow conditions. This work has been extended to reduced graphene oxide functionalized with hemin as a catalytic platform for PON oxidative detection. Boron-doped diamond electrodes (BDD) have been used as platforms for electrochemical detection of a number of analytes in environmental samples as well as in biological media. BDD electrodes have the advantage to provide a relatively wide electrochemical window as well as low capacitive currents. In the present paper we compare and contrast the direct electrochemical oxidation of peroxynitrite on BDD and the catalytic oxidation of PON on modified diamond electrodes as potential sensing platforms of PON. Boron-doped diamond based microarray electrodes have been proposed as potential devices for neuronal stimulation. We hypothesize that PON generated at the array-tissue interface is a major cytotoxic intermediate leading to ultimate tissue death. Developing sensing electrodes based on catalytic detection of PON on boron-doped diamond electrodes is a step towards using individually addressable electrodes in a BDD electrode array for both electrical stimulation and monitoring of PON levels as a predictor of tissue deterioration and, ultimately, death. Understanding the fundamental processes involved during the catalytic oxidation of PON on modified BDD offers the possibility to fine-tune the surface to optimize PON detection.
A New Kind of SERS Active Substrate Using a Film of Densely Packed Gold Nanoparticles
Authors: Rutherford Gugu , Farrell Monique , Xiao Bo , Carvajal Christian G , Santiago Kevin , Pradhan Aswini K
Published: February 2020

In the past two decades there has been a developing interest in using surface plasmon resonance materials for biosensors, environmental sensors, and medical devices due to their ability to identify lower concentrations of analytes. Surfaced Enhanced Raman Spectroscopy has been a useful technique to understand the plasmonic behavior of materials. This research team has developed a novel method for fabricating a highly densely packed film of green synthesized gold nanoparticles using UV irradiation with a UV light source at 254nm and 185 nm.  Raman spectroscopy was used to characterize the densely packed film, and   the surface of the film was functionalized with Rhodamine 6G probe molecules to monitor the SERS activity and identify an enhancement factor. Various proteins were immobilized to the surface of the densely packed gold nanoparticle film, and a SERS measurement was taken to identify the films capability  of detecting low concentration of proteins.  This experimental data has shown the proof of concept for the development of a cost effective and simple method to fabricate SERS substrates specifically for the development of biosensors for the detection of proteins.
Titanium Dioxide and Tin Oxide Composite for so2 Gas Sensors
Authors: Mulmi Suresh , Thangadurai Venkataraman
Published: February 2020

We present the synthesis and utilization of semiconducting metal oxide composites of SnO2 and TiO2 composites (ST) to serve as a SO2 sensor for a range of applications including carbon capture and storage (CCS), enhance oil recovery (EOR) etc. ST-series pellets were prepared by conventional solid state synthesis approach (~700 oC in air), where the size of the pellet was ~1 cm in diameter. The chemical and thermal stability was demonstrated by employing scanning electron microscopy (SEM) and powder X-ray diffraction (PXRD). The average grain size of as-prepared ST composites was obtained in few nanometers. The as-prepared ST pellets were tested for the sensing properties of SO2 gas in ppm level. The effect of temperature was studied to optimize the operating temperature using Pt electrodes as current collector by applying a constant external potential (~100 mV). As-prepared ST2575 with 0.25 mol % SnO2 exhibited an excellent sensing properties for SO2 (10-40 ppm) at 450 oC. For the sensing measurements, SO2 gas was diluted in N2 gas by maintaining the total flow rate at 100 sccm. The t
90 (90% of response time) for ST2575 was found to be ~5 mins. The stability of the sensor was satisfactory for gas sensing measurements in optimized conditions.
Electrochemical Detection of Antibiotics in Environmental Matrices Using Functionalized Boron-Doped Diamond Electrodes
Authors: Chaplin Brian P. , Gayen Pralay
Published: February 2020

Ciprofloxacin (CIP) is a widely prescribed fluoroquinolone antibiotic used in health care and agricultural industries to treat against human and animal bacterial diseases. Due to the fact that only a portion of the antibiotic is metabolized during administration to humans and livestock, large loads of CIP are delivered to watersheds via agricultural runoff or wastewater discharge. The presence of antibiotics in the environment may cause the proliferation of bacterial drug resistance. For this reason the development of sensitive and selective sensors to monitor antibiotics in the environment is an active area of research. In this work, we discuss the development of selective electrochemical sensors through the functionalization of boron-doped diamond (BDD) film electrodes. Sensors are developed by functionalizing the BDD surface with a layer of multi-walled carbon nanotubes (MWCNTs) and a templated-Nafion film. Experiments show that the CIP templated-Nafion film enabled CIP detection at the BDD surface by modifying the polymer pore size and electrostatically excluding anionic species. This templating procedure was shown to be effective for selectively detecting CIP in the presence of other fluoroquinolones (i.e., amoxicillin) and other non-target water constituents (i.e., Cl-, Ca2+, salicylic acid). Additionally, the addition of MWCNTs significantly lowered the detection limit by increasing the specific surface area of the sensor and by promoting specific adsorptive interactions between CIP and surface functional groups of the MWCNTs. Differential pulse voltammetry scans showed that a detection limit as low as 5 nM could be achieved at a pH of 4.5. Linear current response with respect to CIP concentration was achieved up to concentrations of 15 μM, and the peak current response was on the order of 2.8 μA/μM. This sensor platform was extended to other fluoroquinolone antibiotics in order to develop sensor arrays for the simultaneous detection of a number of antibiotics in environmental matrices.
Application of PVC Membrane Sensor in Pharmaceutical and Environmental Analysis. One Example: Potentiometric Determination of Moxifloxacin in Some Pharmaceutical Formulation Using PVC Membrane Sensors
Authors: Mostafa Gamal Abdel-Hafiz
Published: February 2020

PVC membrane sensor using different approach e.g. ion-pair, ionophore, and schiff-base has been used as testing membrane sensors. Analytical applications of membrane sensors for direct measurement of variety of different ions in complex biological and environmental sample are reported. The most important step of such PVC membrane sensor is the sensing active material. The potentiometric sensors have some outstanding advantages including simple design, operation, wide linear dynamic range, relative fast response time, and rotational selectivity. The analytical applications of these techniques to pharmaceutical compounds in dosage forms are also discussed.

The construction and electrochemical response characteristics of Poly (vinyl chloride) membrane sensors for moxifloxacin HCl (MOX) are described.  The sensing membranes incorporate ion association complexes of moxifloxacin cation and sodium tetraphenyl borate (NaTPB) (sensor 1), phosphomolybdic acid (PMA) (sensor 2) or phosphotungstic acid (PTA) (sensor 3) as electroactive materials. The sensors display a fast, stable and near-Nernstian response over a relative wide moxifloxacin concentration range (1 ×10-2  -  4.0×10-6, 1 × 10-2 - 5.0×10-6, 1 × 10-2 - 5.0×10-6 M), with detection limits of 3×10-6, 4×10-6 and 4.0×10-6 M for sensor 1, 2 and 3, respectively over a pH range of 6.0 - 9.0.  The sensors show good discrimination of moxifloxacin from several inorganic and organic compounds. The direct determination of 400 mg/ml of moxifloxacin show  an average recovery of  98.5, 99.1 and 98.6 % and a mean relative standard deviation of 1.8, 1.6 and 1.8% for sensors 1, 2 and 3 respectively.  The proposed sensors have been applied for direct determination of moxifloxacin in some pharmaceutical preparations. The results obtained by determination of moxifloxacin in tablets using the proposed sensors are comparable favorably with those obtained using the US Pharmacopeia method.  The sensors have been used as indicator electrodes for potentiometric titration of moxifloxacin.
X-Ray Photoelectron Spectroscopy and Raman Scattering Studies of ALD Alumina Coated ZnTe Nanowires
Authors: Pradhan Kallol , Sahoo Satyaprakash , Peng J H , Yu H , Dey S K , Katiyar Ram S.
Published: February 2020

Semiconductor nanowires (NWs) represent a versatile platform for evaluating novel phenomena at the nanoscale and also exhibit high potential for applications in future electronic, photovoltaic, and optoelectronic devices [1]. Moreover, the fabrication of core-shell heterostructures based on semiconductor NW-insulator heterostructures further enable the generation of devices with diverse functions. In this work, the fabrication of core-shell heterostructures, via metal-catalyzed vapor–liquid–solid synthesis of Zinc Telluride (ZnTe) NWs followed by the conformal coating of alumina (Al2O3) by atomic layer deposition (ALD), has been demonstrated.  While the former is a direct band gap (~ 2.26 eV), II-VI semiconductor in the blue-green region of the spectrum, the latter is a high band gap (~ 6.4 eV) insulator that is amorphous. Here, preliminary x-ray photo electron spectroscopy (XPS) and Raman scattering results on the ZnTe/Al2O3 core-shell nanostructures are presented and discussed. Additionally, photoluminescence spectra of coated and uncoated ZnTe NWs are discussed in light of the variations in peak position and line-width.

Reference:

1. J. Wallentin, et al, InP nanowire array solar cells achieving 13.8 % efficiency by exceeding the ray optics limit,
Science 339, pp. 1057-1060, (2013).
Preparation of Buckypaper By Surface Modified Multi-Walled Carbon Nanotubesfor Oxygen Reduction Reaction in PEMFC
Authors: Ye Licheng , Zheng Junsheng , Li Ping , Gao Yuan
Published: February 2020

As the key material of proton exchange membrane fuel cell (PEMFC), the carbon supported Pt nanoparticles are the most widely used catalyst for cathode and anode of PEMFC.

Recently we reported anultra-low Pt loading catalytic layer based on buckypaper for oxygen reduction reaction1. The buckypaper is a double-layer thin film containing a multi-walled carbon nanotubes rich surface and a carbon nanofibers rich surface. And Pt has a gradient distribution in this catalytic layer in order to reduce the Pt content.

In this paper, varies of surface modification methods for MWNTs,such as oil-bath acidic reflux, ultrasonic and microwave treatment, were systematically studied,and the oxygen reduction activity of those treated MWNTs were measured. The results showed that surface modified MWNTs have better oxygen reduction reaction activity than the as received MWNTs. Among those treatments, microwave treated MWNTs have better performance than other treatments. Next step buckypaper will be prepared by surface modified MWNTs. As surface modification can also enhance the dispersion of the catalyst2, it has a potential to show good ORR performance in a low Pt loading thus reduce the cost of catalyst.

Acknowledgments

The authors acknowledge the support from the Shanghai Rising-Star Program (11QA1407200), the National Natural Science Foundation of China (21006073), the Scholarship Council and the Fundamental Research Funds for the Central Universities at Tongji University.

Reference

J.Zheng, T.Tian,Y. Gao, Q. Wu, J. Ma, J. Zheng. Int. J. Hydrogen.Energ, 39(2014) 13816.

Y. Xing, L. Li, C. Chusuei, R. Hull. Langmuir, 21 (2005) 4185.

Figure 1
(Invited) Non-Resonant Absorption in Carbon Nanotubes
Authors: Vialla Fabien , Malic Ermin , Langlois Benjamin , Chassagneux Yannick , Lauret Jean-Sébastien , Voisin Christophe
Published: February 2020

Absorption spectroscopy of large ensembles of carbon nanotubes show marked resonances, attributed to the different exitonic levels of each chiral species, as well as a relatively smooth background. This signal consists of a large number of different intrinsic and extrinsic contributions, such as phonon sidebands, amorphous carbon absorption, light scattering... It is therefore challenging to extract any quantitative information from these direct absorbance measurements.

In contrast, photoluminescence excitation measurements in semi-conducting nanotubes give access to the intrinsic non-resonant absorption contribution between the excitonic resonances. Using a global analysis method, we were able to delineate the contribution of each chiral species including its tiny non-resonant component that shows up as 0.5 eV wide plateaus between the excitonic resonances. By comparison with the recently reported excitonic absorption cross-section on the S22 resonance, we found a universal non-resonant absorption which turns out to be of the order of one half of that of an equivalent graphene sheet. This value as well as the absorption line-shape in the non-resonant window is in excellent agreement with microscopic calculations. This non-resonant absorption cross-section is the same (within our resolution) for all the chiral species we measured in this study.
Hydrogen-Bromine RFB :Electrochemical Measurements and Cell Performance of a 40cm² H/Br-RFB System
Authors: Küttinger Michael , Noack Jens , Elazari Ran , Costi Ronny , Tübke Jens
Published: February 2020

Conventional redox flow batteries (RFB) use electrolyte solutions as energy storage media. For this reason the energy density is mainly limited by the solubility of the redox couples in the solutions. The kinetics of the reactions is mostly moderate so that cycling power densities can only reach max. 100 mW/cm². Depending on the energy / performance ratio the cost of the energy converter of RFBs clearly dominates the total investment costs. For longer storage periods the influence of the cost of the energy storage medium increases. For these reasons RFBs with redox pairs with high kinetics and thus a high power density are desirable. Hydrogen and bromine-based energy storage fulfill both requirements because the kinetics of the reactions are very fast and both elements are inexpensive and very abundant. In addition potentially high energy densities and efficiencies can be achieved.

Anode:                H2 -> 2 H+ +2 e-                 E0 = 0.00 V

Cathode:             Br2 +2 e- -> 2 Br-               E0 = + 1.06 V

Cell:                     H2 + Br2 -> 2 HBr               E = 1.06 V

Although the first studies were made in the 80s of the last century [1], the research intensified due to these positive characteristics in the last years [2, 3]. For a viable use, hydrogen storage, bromine diffusion, bromine complexation and system behavior are the biggest challenges.

In this work we want to present the results of the development and the construction of an H/Br-RFB with an active area of 40 cm² and its behavior at different electrolyte compositions, temperatures and current densities. For better identification of the properties the half-cell potentials and impedances were also measured and evaluated. This research forms the basis for our future studies  involving the use of advanced bromine complexation agents (BCAs) and their impact on H/Br-RFB.

 [1] Yeo, R. S.; Chin, D. ‐T. (1980): A Hydrogen‐Bromine Cell for Energy Storage Applications. In: Journal of The Electrochemical Society 127 (3), S. 549–555. DOI: 10.1149/1.2129710.

[2] Cho, Kyu Taek; Albertus, Paul; Battaglia, Vincent; Kojic, Aleksandar; Srinivasan, Venkat; Weber, Adam Z. (2013): Optimization and Analysis of High-Power Hydrogen/Bromine-Flow Batteries for Grid-Scale Energy Storage. In: Energy Technology 1 (10), S. 596–608. DOI: 10.1002/ente.201300108.

[3] Cho, Kyu Taek; Tucker, Michael C.; Ding, Markus; Ridgway, Paul; Battaglia, Vincent S.; Srinivasan, Venkat; Weber, Adam Z. (2014): Cyclic Performance Analysis of Hydrogen/Bromine Flow Batteries for Grid-Scale Energy Storage. In: ChemPlusChem, S. n/a. DOI: 10.1002/cplu.201402043.

Figure 1
Solid Particle Flow Battery Design and Characterization
Authors: Koenig Gary , Qi Zhaoxiang
Published: February 2020

Classic flow battery systems have consisted of transition metals dissolved in aqueous solvents which provide the electroactive materials.  These flow battery systems have relatively low energy densities due to the stability window of water limiting the operating voltage and the solubility of the transition metals limiting the practical capacity.  Recently, a few research groups have explored flow batteries with solid particles as the electroactive materials, in an effort to increase the energy density of the catholyte and anolyte materials.  Many of these reported systems have extremely high viscosities because of the high solid particle loadings in the electrolyte.  These high viscosities will result in high energy demands for the pumping of the electroactive fluids.  Our group has been working on flow battery systems that take advantage of the energy density advantages of solid particles, but with a goal of not having prohibitive parasitic energy losses from pumping these fluids through the flow battery system.  This work will describe the design and characterization of a flow battery that operates at reasonable viscosities for a particle-laden electrolyte, and the observed coupling between electrochemical properties and rheological properties in a solid particle flow battery system.
Feasibility of All-Copper Hybrid Redox Flow Battery for Large Scale Energy Storage
Authors: Stricker Elizabeth A. , Savinell Robert F. , Wainright Jesse S.
Published: February 2020

Copper redox flow batteries have been newly studied and offer many advantages over other redox flow battery chemistries [1-3].  There is little hydrogen evolution, no dendrite formation has been observed, and it is an all copper system which indicates no crossover contamination. Preliminary analysis indicates an open circuit voltage of 0.81 volts as shown in Figure 1.Although the all copper redox flow battery has a relatively low open circuit voltage, the all copper redox flow batter provides a platform for a simple and cost-effective flow battery system. In this research, the all copper redox flow battery in bromide electrolyte has been studied in a prototype 6.45 cm2electrode single cell. Charge-discharge cycling achieved coulombic efficiencies over 85% and voltaic efficiencies greater than 75%. However, capacity fade was observed and preliminary results suggest this is due to metallic copper loss at the negative electrode. This is most likely due to non-ideal plating morphologies which have been studied independently as a function of current density and electrolyte composition. We will report on our cell testing and single electrode experiments for this promising flow battery chemistry.

Figure 1: Cyclic voltammogram of 0.5M Cu1+  in 4M NaBr, 1M HBr, and 0.5M Br-. This is the last of 5 cycles at a scan rate of 10 mV/s, on a graphite working electrode, and using a silver-silver chloride reference electrode. The Cu0/1+ and Cu1+/2+ standard potentials are approximately -0.26 and 0.55 volts, respectively indicating the all copper redox flow battery has an open circuit potential of 0.81 volts.

References:

[1] D. Lloyd, T. Vainikka, K. Kontturi, Electrochimica Acta, 100 (2013) 18-23.

[2] L. Sanz, D. Lloyd, E. Magdalena, J. Palma, K. Kontturi, Journal of Power Sources, 268 (2014) 121-128.

[3] L. Sanz, D. Lloyd, E. Magdalena, J. Palma, M. Anderson, K. Kontturi, Journal of Power Sources, 278 (2015) 175-182.

Figure 1