bluuebunny/crossref_metadata_2025_split huggingface dataset:
Thermal & Humidity Stability of Mn4+ Doped Complex Fluoride Phosphors
Authors: Sista Srinivas P , Murphy James , Garcia-Santamaria Florencio , Setlur Anant A 
Published: February 2020

Mn4+ doped complex fluoride based red phosphors have the potential to improve efficiency and color quality (CRI & R9) in LED lighting systems and enhance color gamut for LED displays. Owing to low absorption of Mn4+, high Mn4+ doping concentration is necessary to enable low CCT applications. One of the issues with Mn4+ doped phosphors is their high temperature and high humidity (HTHH) stability which is even more important for high Mn4+ doping. Here we will discuss the various post synthesis treatment techniques that help improve HTHH stability of Mn4+
doped fluoride phosphors.
Cooperative and White Light Emission from Yb- and Yb,Er-Doped Y2Si2O7 Nanopowders
Authors: Di Bartolo Baldassare , Erdem Murat , Collins John , Sitt Bryan , Ligouri Joseph 
Published: February 2020

We have investigated the luminescence properties of of Y2Si2O7 nanopowders doped with (1) Yb only and (2) Yb and Er. Under 980 nm excitation of the Yb-only sample, the system exhibits a blue emission, which we attribute to cooperative emission from Yb pairs. When the air pressure in the sample holder is reduced to very low pressures, a broad band “white” emission, extending from the blue into the near IR, appears, and the blue Yb emission band disappears. In the Yb-Er doped system, no cooperative emission from Yb is observed, but the Er emission bands are observed throughout the visible region. These Er emissions result from upconversion processes through energy transfer or through a combination of energy transfer and excited state absorption. The broad band white light emission is also observed in this sample, and becomes the more favorable emission as the pressure is decreased and the pumping intensity increased.
Electrochemical and Catalytic Properties of Liver Microsomes Adsorbed to Magnetic Nanoparticles
Authors: Nerimetla Rajasekhara , Krishnan Sadagopan 
Published: February 2020

Subcellular liver fractions (microsomes) act as an ideal in-vitro system to study the pharmacokinetics, drug metabolism and drug-drug interactions of new drugs. Therefore, developing microsomes based biosensors and bioreactors have immense significance in green drug metabolites, stereoselective chemical compound synthesis and drug sensing. Magnetic nanoparticles (MNP) have unique advantages such as large surface area and high loading capacity for enzymes/proteins which can enhance the electrochemical properties such as heterogeneous electrons transfer kinetics and catalysis.[1] Also our prior studies have shown edge plane pyrolytic graphite electrodes to exhibit good electron transfer kinetics and film stability when immobilized with microsomes.[2] In the present study, our objective was to use amine functionalized MNP to adsorb complex drug metabolizing microsomes on edge plane pyrolytic graphite electrodes without the need to isolate and purify enzymes to develop volume efficient bioreactors. The electrochemical properties and electrocatalytic conversion of a drug into its metabolite for the constructed bioelectrode will be discussed.

Acknowledgements: We are grateful for the financial support by the National Institute of Diabetes and Digestive and Kidney Diseases of the National Institutes of Health under Award Number R15DK103386.

[1] S. Krishnan, and C.Walgama, Anal. Chem. 2013, 85, 11420−11426.

[2] C. Walgama, R. Nerimetla, N. F. Materer, D. Schildkraut, J. F. Elman, and S. Krishnan, Anal. Chem. http://dx.doi.org/10.1021/ac5044362
Bimetallic Iron and Nickel Nanoparticles for the Electrocatalytic Oxidation of Methanol and Ethanol for Fuel Cells
Authors: Candelaria Stephanie L , Bedford Nicholas , Greenlee Lauren F 
Published: February 2020

The electrochemical oxidation of alternative fuels, such as methanol and ethanol, for alkaline fuel cells often relies on the use of precious metal catalysts. However, the scarcity and high cost of these Pt group metals (Pt, Pd, Au, etc.) leads to the search for earth-abundant alternatives with similar electrocatalytic properties. Among these, iron emerges as a promising candidate as it has already been shown to have high activity for a variety of reactions. However, the rapid formation of oxides severely limits the stability of the iron nanoparticles. The addition of a second metal, such as nickel, slows this oxidation and can also enhance catalytic activity of the nanoparticles. In this work, bimetallic iron-nickel nanoparticles are synthesized in aqueous conditions at room temperature and pressure. Slight changes in the synthesis leads to significant differences in the size, stability, and lifetime of the nanoparticles. Possible explanations for these differences are characterized through both ex situ and in situ experiments. During electrochemical measurements, these materials show two distinct regions where redox reactions are taking place, which may correspond to nickel and iron reacting separately. The effects of various testing parameters on the electrochemical behavior are also explored.
Effect of High Energy Carbon Beam Irradiation on Carbon Nanotubes Modified Glassy Carbon and Its Application in Sensing of Deoxyguanosine
Authors: Goyal Rajendra N , Sharma Rosy , Gupta Pankaj 
Published: February 2020

The effect of high energy carbon ion beam as the modification tool for the multiwalled carbon nanotubes (MWCNT) modified glassy carbon (GC) has been studied. The change in the morphology, length and diameter of the carbon nanotubes upon irradiation is analyzed using Raman spectroscopy, Atomic force microscopy and FE-SEM. The irradiated MWCNTs had a diameter in the range of 3-27 nm which is much lower in comparison to the diameter of the tubes present in the pristine state. All the bands in the Raman spectra, corresponding to the irradiated MWCNT, shifted towards higher wave numbers by 4-5 cm-1. The irradiated MWCNT/GCE has been further used as a sensor for the electrochemical investigation of deoxyguanosine and deoxyadenosine. A sharp oxidation peak with much enhanced peak current at ~930 mV, corresponding to the oxidation of deoxyguanosine, is observed at the irradiated sensor, whereas, no peak was observed at the bare GCE. A very small peak at ~ 975 mV is observed at MWCNT modified GCE. Thus, it can be concluded that irradiation leads to appreciable defects formation which promotes the electron transfer and leads to enhanced electrooxidation of deoxyguanosine on the irradiated sensor surface.
It was found that the peak potential of both deoxyguanosine and deoxyadenosine depends on the pH of the supporting electrolyte and shifted to more positive potentials with increase in pH. The linear relation between pH and the peak potential (Ep) can be expressed by the following equations:
Ep (Deoxyguanosine) = -52.96 pH + 1307.3 (R2 = 0.9928)
Ep (Deoxyadenosine) = -49.94 pH + 1560.4 (R2 = 0.9990)
From the linear current versus concentration relations, it can be seen that exposure of MWCNT to high energy carbon beam lead to ~ 7 times increase in sensitivity in the case of deoxyguanosine and ~ 2 times for deoxyadenosine. The limit of detection, calculated by 3σ/b where σ is the standard deviation of the blank solution and b is the slope of the calibration curve, is substantially changed on irradiation from 12 µM to 507 nM and 4.29 µM to 300 nM for deoxyguanosine and deoxyadenosine respectively. The simultaneous determination of the two analytes was performed using the fabricated sensor and its practical utility was tested by analyzing DNA, extracted from herring sperm and MCF7 cell line, for the presence of deoxyguanosine and deoxyadenosine. The common biomolecules present in blood and urine did not interfere in the determination and the high stability and reproducibility of the sensor confirmed its successful application in real sample analysis.

Figure 1
Impedance of Mediated Electrochemical Processes: Fenton Reaction
Authors: Polczynski Piotr , Jurczakowski Rafal Robert 
Published: February 2020

Impedance is a powerful technique that provides a deep insight into the mechanism, kinetics, and thermodynamics of various physicochemical processes. Impedance of electrochemical systems coupled with homogeneous chemical reactions is seldom reported. Catalytic processes governed by the EC′ mechanism are of particular relevance since these processes are widely employed for mediated electrochemical oxidation of persistent environmental pollutants, gas sensing, catalytic hydrogen evolution, carbon dioxide electroreduction, enzyme oxidation, electrochemistry of nucleic acids, amino acids, as well as for numerous other bioanalytical applications. These system has been investigated almost exclusively by using classical transient electrochemical methods.
Recently we have developed an analytical expressions describing the faradaic impedance of the catalytic processes governed by (pseudo) first-order chemical kinetics. The solution was obtained in the rigorous treatment and it is applicable to the analysis of the experimental EC’ systems regardless the kinetics of the homogeneous and electrochemical steps.1 We have found that unequal diffusivities of the oxidized and reduced forms of the redox mediator have a strong effect on the impedance characteristics of the catalytic EC’ systems. This behavior is related to the novel impedance element, which reduces to the Gerischer impedance when both diffusion coefficients are equal.1

In this study we demonstrate how to fully characterize EC’ type processes by using impedance spectroscopy and our model. Provided equivalent circuit together with potential dependence of all impedance parameters allow for a rapid and precise determination of all kinetic and thermodynamic parameters of EC’ type reactions. For Fenton reaction, the formal potential, E
0’, heterogeneous, k
0, and homogeneous, k, rate constants, electron transfer coefficients, α, β, and both diffusion coefficient of the redox mediator D
ox, D
red were precisely determined. Greater part of these parameters have been determined here for the first time while the other are in good agreement with the previous literature reports.
[1] R. Jurczakowski and P. Polczynski, J Phys. Chem. C, 2014, 118, 7980-7988.
Novel Methanol-Tolerant Metal Selenide Based Chalcogenide Electrocatalysts for Oxygen Reduction in Alkaline Solution
Authors: Masud Jahangir , Swesi Abdurazag , Nath Manashi 
Published: February 2020

Direct methanol fuel cells (DMFCs) have been studied as an alternatives of conventional energy-generating devices due to their high energy density and low-to-zero emissions. Although significant advancements have been achieved for DMFCs in recent years, unremitting efforts are still needed to make them commercially applicable. The methanol “cross-over” phenomenon, the permeation of alcohol through the membrane, remains as one of the major problems for the widespread commercialization.1 In order to overcome this drawbacks, efforts are focused in the development of a new cathode electrocatalysts that do not adsorb methanol while maintaining an excellent activity for the oxygen reduction reaction. Here, we demonstrate transition metal selenide, Mx
Sey (M = Co, Ni) based electrocatalysts for oxygen reduction reaction (ORR) in alkaline solution which also exhibit high methanol tolerance.
Electrocatalysts were prepared by electrodeposition on GC electrodes. These catalysts exhibited excellent ORR activity in presence of methanol in 0.1 M KOH solution. The onset potentials for ORR in 0.1M KOH solution were found to be 0.85 and 0.9 V (vs. RHE) for NixSey and CoxSey, respectively, which even didn't change in presence of methanol. The catalysts were characterized using TEM, SEM, EDX, XRD and XPS for morphology, elemental chemical compositions, phases and electronic states. Figure 1 shows SEM images of the catalysts (NixSey and CoxSey). The detailed electrochemical studies along with catalytic activities will be presented in the meeting.
Reference:
N. Jung, Y. H. Cho, M. Ahn, J. W. Lim, Y. S. Kang, D. Y. Chung, J. Kim, Y.H. Cho, Y.E. Sung, International J. of Hydrogen Energy, 2011, 36, 15731.

Figure 1
Electron Transfer Studies Between New Fad-Dependent Glucose Dehydrogenase and Different Osmium Polymers (Applications in Biosensors and Biofuel Cells)
Authors: Aslam Iqra , Zafar Muhammad Nadeem , Ludwig Roland , Leech Dónal , Gorton Lo 
Published: February 2020

A new extracellular flavin adenine dinucleotide (FAD)-dependent glucose dehydrogenase from Glomerella cingulata (GcGDH) was electrochemically studied as a recognition element in glucose biosensors. The redox enzyme was recombinantly produced in Pichia pastoris, homogeneously purified and its glucose oxidizing properties on spectrographic graphite electrodes were investigated. Six different Os-polymers, the redox potentials of which ranging in a broad potential window between +15 and +489 mV vs. NHE, were used to immobilize and “wire” GcGDH to the spectrographic graphite electrode’s surface. The GcGDH/Os-polymer modified electrodes were evaluated by chronoamperometry using flow injection analysis. The current response was investigated using a step-wisely increased applied potential. It was observed that the ratio of GcGDH:Os-polymer and the overall loading of the enzyme electrode significantly affect the performance of the enzyme electrode for glucose oxidation. The best suited Os-polymer [Os(4,4¢-dimethyl-2,2¢-bipyridine)2(PVI)Cl]+ had a potential of +309 mV vs. NHE and the optimum GcGDH:Os-polymer ratio was 1:2 yielding a maximum current density of 493 µAcm-2at a 30 mM glucose concentration.

Key words: Glucose dehydrogenase, FAD, Os-polymers, glucose biosensor, chronoamperometry, oxygen reactivity.
Empirical Insights into the CO2 Reduction Reaction Mechanism: A Study of the Reduction of CO2, CO and Formaldehyde on Cu Electrodes By Differential Electrochemical Mass Spectrometry
Authors: Javier Alnald , Chmielowiec Brian , Sanabria-Chinchilla Jean , Kim Youn-Geun , Baricuatro Jack Hess , Soriaga Manuel P 
Published: February 2020

This work describes results from a first-ever attempt to employ differential electrochemical mass spectrometry (DEMS) of selectively pre-adsorbed reactants and (postulated) intermediates as a supplementary experimental approach in the study of electrocatalytic reaction mechanisms. For the specific case of the Cu-catalyzed electrochemical reduction of CO2, dilute solutions of CO2, CO and HCHO in aqueous KHCO3 were placed separately in a DEMS stationary thin-layer electrochemical cell in contact with a Cu electrode. Simultaneous faradaic-current (CV) and mass-spectrometric-current (MSCV) voltammograms were then obtained for each solution. The only reduction products detected by mass spectrometry were H2, CH4, H2C=CH2 and CH3CH2OH; CO was also assayed but only from the reduction of CO2.
The results prompt the following empirical inferences: (i) The slight but not imperceptible drop in the hydrogen-evolution current may not be caused by CO poisoning. It also exists for HCHO, a more feeble adsorbate, in the absence of the monoxide. In addition, the adsorption strength of H2 is four times greater than that of CO. (ii) CO is the first product of CO2 reduction, as well as the first intermediate in more advanced reactions that include formation of pure and oxygenated hydrocarbons; this is in conformity with the (almost) unanimously held view. (iii) HCHO is not a precursor for C=C double-bond formation. (iv) HCHO is a secondary intermediate for the production of methane and ethanol. (v) The generation of CH4 and CH3CH2OH from adsorbed CO occurs via two pathways: one requires a theoretically postulated surface species, CO protonated on the C atom, and the other involves adsorbed HCHO, constituted after the rate-limiting protonation step. (vi) The generation of CH4 and CH3CH2OH from CO has a much higher activation barrier than conversions from HCHO; not unexpected since the reactions transpire after the slow Cu–OCH+ formation and, consequently, are not highly activated.
Determination of Battery Stability with Advanced Diagnostics
Authors: Lamb Joshua , Orendorff Christopher J , Christophersen Jon 
Published: February 2020

The increasing demand of lithium ion batteries for vehicle electrification is changing the typical use conditions that batteries may see. Over time, batteries may develop defects that are difficult to detect with traditional measurements. It is also possible that batteries may be left in an unknown state after failure of the monitoring system, loss of communication, or a potentially damaging event (such as an auto accident). It is therefore useful to explore other monitoring and interrogation methods that can better determine the stability of a battery in an unknown state. This work explores the use of electrochemical impedance spectroscopy as a method to determine the stability of batteries by observing changes in the complex impedance measurement as the cell is exposed to abusive conditions. Very dramatic changes to the internal resistance were observed when single cells were exposed to abusive conditions, suggesting that even single frequency impedance measurements could be effective with single cells. However tests on three cell series and parallel strings yielded smaller changes, primarily to the charge transfer resistance, showing that complex impedance measurements are more appropriate as the system increases in complexity. A rapid impedance tool developed at Idaho National Laboratory was tested and compared to traditional potentiostat tools as well. This was shown to yield similar data to the traditional tools, providing a potential method for continuous monitoring of a battery system. It was observed, however, that shifts in the data are difficult to detect in very transient systems.
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.
Numerically Characterizing Nail Penetration Testing for Safety Evaluation of Li-Ion Cells
Authors: Yang Chuanbo , Kim Gi-Heon , Keyser Matthew , Pesaran Ahmad 
Published: February 2020

Multi-physics modeling was performed for better understanding the nature of nail penetration testing. Nail penetration test is a mechanical abuse technique used to evaluate battery safety performance by inducing battery internal short circuits (ISC). With specified battery chemistries and form factors, it has shown nail penetration results are affected by a number of test parameters, including battery sizes, short resistances caused by mechanical failure, nail penetration locations, speeds, depths, nail materials and diameters etc. Due to the lack of sufficient understanding of relationships between testing parameters and outcomes, nail penetration test could give inconsistent results and is not able to provide desired reliability.
3D multi-physics modeling of nail penetration process was carried out to quantify testing parameter influence. This objective is not feasible to be achieved by testing approaches, not only since nail penetration is a high dynamic process involving multi-physical behaviors, but measurement data is insufficient. The model applied in this study is able to estimate battery dynamic responses under nail penetration tests by integrating a series of physical-based sub-models. The initial consequence of nail punch damage, short circuits, was addressed as an input variable.
Utilizing this model, outcome difference between a nail penetration test and a real ISC case scenario was identified. Simultaneous battery behaviors along nail movement in the battery were captured. Parameter studies were conducted to quantify the effect of selected testing parameters, e.g. nail penetration speeds, depths and locations. The numerical results provide in-depth insights for understanding the nature of nail penetration testing and improve safety testing reliabilities.
Formic Acid Oxidation on Platinum- a Simple Mechanistic Study
Authors: Schwarz Kathleen , Sundararaman Ravishankar , Moffat Thomas , Allison Thomas 
Published: February 2020

The oxidation of small organic acids on noble metal surfaces under electrocatalytic conditions is important in industrial processes and of scientific interest, but the basic reaction mechanisms continue to be a matter of debate. Formic acid oxidation on platinum is one of the simplest of these reactions, yet even this model system remains poorly understood. Historically, proposed mechanisms for the oxidation of formic acid involve the acid molecule as a reactant, but recent studies suggest that the formate anion is the key reactant instead. Ab initio studies of this reaction do not address formate as a possible reactant, due to the difficulty of calculating a charged species near a solvated surface under potential control. Using the recently-developed Joint Density Functional Theory (JDFT) framework for electrochemistry, we perform ab initio calculations of this reaction on a Pt(111) surface to explore this reaction and help resolve the debate. When a formate anion approaches the platinum surface with H pointing towards the surface, it reacts to form CO2 and adsorbed H with no barrier on a clean Pt surface at relevant voltages. This mechanism explains the elusiveness of an active surface intermediate and leads to a reaction rate proportional to formate concentration and number of available platinum sites. Additionally, high coverages of adsorbates lead to large reaction barriers, and consequently, we expect availability of pristine metal sites to limit the experimentally observed reaction rate.
Nano-Impact Electrochemistry for Assessing the Chemical Reactivity of Nanoparticles
Authors: Karimi Anahita , Andreescu Daniel , Andreescu Silvana 
Published: February 2020

The electrochemical study of particle impacts on electrode is a rapidly developing field which provides the extensive capabilities of nanoparticle detection and characterization. It has demonstrated significant promise for quantification of nanoparticles and characterization in terms of nanoparticle coatings and catalytic activity. In this presentation, we describe the development of an electroanalytical collision technique to characterize the fundamental surface properties, functionalization and redox reactivity of metal and metal oxide nanoparticles by nano-impact electrochemistry. We will demonstrate the potential of this method: (1) as a screening tool of particle reactivity, (2) study of the adsorption/desorption of environmental contaminants with single particle resolution, and (3) extract mechanistic information that would be predictive of the chemical reactivity of nanoparticles for various applications. We will discuss the potential of this approach to complement or replace costly characterization techniques and enable routine study of nanoparticles and their reactivity.
Efficient Solar-to-Hydrogen Production Materials and Devices
Authors: Wang Heli , Ager Joel W. , Gaillard Nicolas , Miller Eric Lars 
Published: February 2020

Renewable hydrogen production via water splitting needs to tackle the challenges of high solar-to-hydrogen (STH) efficiency and high stability of the materials and devices. For photoelectrochemical (PEC) water splitting, semiconductor materials’ band gap, band edge, optoelectronic efficiency, and stability must be satisfied simultaneously to tackle the challenge.
With over five decades of research, different materials and devices have been studied and explored. STH efficiencies of metal oxides have been limited by issues related to the wide band gap, absorption, charge mobility, recombination, interfacial kinetics, etc., those the material class may be stable. Thin films (like III-V and CIGS) offer alternative pathways to efficient STH conversion, with stability remains an issue.
On the other hand, structures and configurations have been developed for unbiased PEC water splitting, mostly in laboratory scale. This presentation will address semiconductor materials, structures and devices developed for solar hydrogen production.