bluuebunny/crossref_metadata_2025 huggingface dataset:
Influence of MPL Structure Modification on Fuel Cell Oxygen Transport Resistance
Authors: Lu Zijie , Waldecker James , Tam Mickey , Cimenti Max
Published: February 2020

Proton exchange membrane fuel cell (PEMFC)) technology is the basis for a promising future automotive powertrain. However,   PEMFC cost must be reduced and durability must be improved. The greatest opportunity to reduce cost is to run the fuel cell at high current density while not considerably lowering the cell voltage [1], which requires excellent mass (both oxygen and water) transport in the fuel cell electrode, as well as low ohmic loss. In this work we report the measurement of the resistances to oxygen transport in the fuel cell cathode electrode and the impact of microporous layer (MPL) structure modification on the oxygen transport.

The oxygen transport resistance is measured by the limiting current density method [2-4] in a specially designed 5 cm2 cell using a variety of O2 concentrations. The total oxygen transport resistance in a fuel cell cathode sums the resistance from the diffusion media and that from the catalyst layer (CL). The CL resistance includes the Knudsen diffusion resistance and the ionomer permeation resistance: Rtot = RDM + RCL = RDM + RCL,Knud + RCL,ion, where  RDM is quantified by varying the cathode gas pressure [2], and RCL,Knud and RCL,ion can be differentiated by varying the temperature [4].

The effect of MPL modification on the oxygen transport resistance has been studied. Straight holes of 20 mm diameter through the MPL, but not through the carbon fiber substrate, were made by a laser perforation technique. The oxygen transport resistances in the cell with the perforated MPL on the cathode were measured and compared to those in the cell with the baseline MPL.   

The total oxygen transport resistance depended on the water production rate, revealing a dry region and a dry-to-wet transition for both MPLs in response to the oxygen concentration increase. The MPL modification had little influence on the total transport resistance in the dry region, while the perforated MPL significantly reduced the transport resistance in the dry-to-wet transition region, indicating the perforated MPL improved the cathode water management. It is not clear at this moment whether the increased transport resistance under the wet condition occurs in the diffusion medium or in the catalyst layer. The transport resistance in the CL can only be obtained for the dry conditions and the MPL modification shows little influence on the CL resistance. A trend of decreasing CL resistance with increasing temperature was observed. This temperature effect is mainly attributable to the oxygen permeation in CL ionomer, while the Knudsen diffusion in CL secondary pores is only weakly dependent on temperature.

References:

DOE Roadmap, 2014.

D.R. Baker, D.A. Caulk, K.C. Neyerlin, M.W. Murphy, J. Electrochem. Soc., 156, B991 (2009).

D.A. Caulk and D.R. Baker, J. Electrochem. Soc., 157, B1237 (2010).

N. Nonoyama, S. Okazaki, A.Z. Weber, Y. Ikogi, T. Yoshida, J. Electrochem. Soc., 158, B416 (2011).
Determination of Permeability of the Gas Diffusion Layer of Proton Exchange Membrane Fuel Cells (PEMFCs)
Authors: Hasanpour Sadegh , Hoorfar Mina , Phillion Andre
Published: February 2020

One vital component in the Proton Exchange Membrane Fuel Cells (PEMFCs) is the Gas Diffusion Layer (GDL). This layer is a pathway for the reactants to reach the reaction site and for the by-products to be removed. Due to this application, the permeability of this layer has been investigated experimentally and numerically [1]. This layer has a highly porous structure, and hence identifying a geometry that resembles best the GDL for modeling flow through this layer is very important. In this study, the 3D image of a GDL sample has been obtained with high resolution imaging, X-ray microtomography, and is used as a model to simulate flow through this layer. This layer typically treated with micro-porous layer (MPL). In this paper, MPL was separated and permeability through the MPL is investigated separately using an image-processing method developed in-house. The results indicate that MPL reduces the permeability of GDL considerably. This work facilitates the study of the effect of MPL on the permeability of the GDL, which is impossible to be determined in experimental approaches [2].

[1] J. Pharoah, "On the permeability of gas diffusion media used in PEM fuel cells," J. Power Sources, vol. 144, pp. 77-82, 2005.

[2] J. Ihonen, M. Mikkola and G. Lindbergh, "Flooding of gas diffusion backing in PEFCs physical and electrochemical characterization," J. Electrochem. Soc., vol. 151, pp. A1152-A1161, 2004.
Photocatalytic Hydrogen Evolution from Earth Abundant Nickel Oxide Clusters Dispersed on MCM-48 Mesoporous Materials
Authors: Peng Rui , Shrestha Khadga , Mishra Gautam , Baltrusaitis Jonas , Wu Chia-Ming , Koodali Ranjit T
Published: February 2020

NiO, as an earth abundant metal oxide that has been extensively studied as a co-catalyst for a variety of photocatalytic reactions, including solar hydrogen generation. Mesoporous materials have been used as a support to disperse spatially isolated semiconductor clusters to minimize photoinduced charge-carrier recombination and enhance photocatalytic efficiency. Such well-dispersed semiconductor particles encapsulated in mesoporous matrices possess small sizes due to quantization effect and higher redox potentials compared with those in bulk. In this work, NiO semiconductors were dispersed onto MCM-48 mesoporous materials and their photocatalytic activities were explored. The physico-chemical properties of all the prepared samples have been investigated using a wide selection of techniques ranging from powder X–ray diffraction (XRD), BET surface area analysis, atomic absorption spectroscopy (AAS), transmission electron microscopy (TEM), UV–vis diffuse reflectance spectra (DRS), and X-ray photoelectron spectroscopy (XPS) and a structure-activity relationship was obtained. The MCM-48 supported NiO materials exhibit significantly enhanced activity and hydrogen evolution rate compared with bulk NiO. The use of MCM-48 cubic phased mesoporous materials facilitates the high dispersion of NiO species and is also conducive to restrain the size of NiO into small clusters. Meanwhile, the presence of both NiO and Ni2O3 species and the formation of the NiO/Ni2O3 heterojunction positive factors for the enhanced photocatalytic activity since the photogenerated charge-carrier can be effectively separated.
Multicomponent Electrocatalytic Systems for Solar Fuels Generators
Authors: Houle Frances A , Toma Francesca M. , Friebel Daniel , Haber Joel A. , Sharp Ian D. , Bell Alexis T.
Published: February 2020

High-functioning catalysts for photoelectrochemical solar fuels generators must operate as part of an integrated system including inorganic semiconductor light absorbers and, often, interfacial corrosion protection layers. These systems are far from idealized single crystals, indeed disorder or nanostructure can be found to be desirable. Correlation of structure, composition and interfacial characteristics with electrocatalytic properties presents an important challenge in achieving efficiency and stability. In this talk we will present an overview of our recent studies on water oxidation catalysts used for solar hydrogen generation systems both in- and ex-situ, and operando, and discuss key factors that affect their reactivity.
Enabling Unassisted Solar Water Splitting By Hematite
Authors: Wang Dunwei
Published: February 2020

As a photoelectrode material for solar water splitting, hematite has received tremendous attention. The appealing properties presented by hematite include earth abundance, stability against corrosion, suitable band gap, and nontoxicity. It, however, also presents a long list of challenges, such as notoriously short hole diffusion distance, poor catalytic activity, and low photovoltage. Among these challenge, the low photovoltage has received the least attention. We have shown that the low photovoltage is a result of combined effects of band edge position mismatch with water redox potentials and poor surface energetics. By interfacing with NiFeOx, an amorphous oxygen evolution catalyst, we have measured greatly improved photovoltages (from 0.24 V to 0.61 V). Importantly, the improved photovoltage was understood as a result of improvement in surface energetics, but not better water oxidation kinetics enabled by NiFeOx. To further test what is the true limit of the photovoltage generation capability by hematite, we recently carried out a detailed structural study on hematite and found that surface defects are responsbile for additional photovoltage lost. A facile regrowth strategy was developed to correct the deficiency. A record-low turn-on voltage of 0.45 V (vs. RHE) was achieved. The results permitted us to construct, for the first time, unassistant water splitting by hematite with a Si photocathode. An overall efficiency of 0.91% was measured.
Solar Fuel Generation By 1D ZnO /QDs Heterostructures
Authors: He Yang , Li Jiangtian , Chu Deryn , Bright Joeseph , Wu Nianqiang
Published: February 2020

Nowadays, with the crisis of the fossil fuels’ depletion and the pollution from these fuels’ combustion, there is a huge demand for clean and sustainable energy source, which makes solar energy extremely appealing. Using a photoelectrochemical cell (PEC) with the semiconductor as a photoanode, the solar energy could be absorbed, converted and stored in hydrogen via water splitting. One-dimensional (1D) nanostructured semiconductors, as a photoanode, are promising with their advantage in photon absorption and charge transport. The solar fuel efficiency could be increased using the hybridized Quantum Dots-1D nanostructure heterojunction. Herein we report the fabrication of QDs/ZnO 1D heterostructure for solar fuel generation. Such band alignment not only extends the light harvesting up to near infrared region, but also forces the forward transfer of the charge carriers, which improves the charge separation and suppresses the charge recombination, and thus ensures the high efficiency. Such 1D nanostructures provide great opportunities for the realization of the solar cell commercialization.
Photoelectrochemical Characterization of Spin-Coated CuBi2O4 Thin Films for Water Splitting
Authors: Rodríguez Gutiérrez Ingrid Guadalupe , Flores Pinto Maricarmen , Rodríguez Pérez Manuel Jesús , Rodriguez-Gattorno Geonel , Oskam Gerko
Published: February 2020

Complex oxides containing multiple cations or in some cases multivalent cations such as Bi3+,5+, Co2+,3+, Sn2+,4+, have attracted much attention for photoelectrochemical applications due to their unique properties. Bismuth has a multivalent nature (Bi3+, Bi5+) that can be present at the same time in the same crystal structure in the Bi site, improving the conductivity of the material. An interesting new p-type semiconductor, which has shown high photocurrent under visible light conditions, is CuBi2O4 [1]. In this work, we present the growth of CuBi2O4 thin films prepared by spin coating method on FTO glass substrate. The precursor solution was prepared using bismuth nitrate, copper nitrate and dilute aqueous acetic acid as a solvent. The films were spin coated and annealed at 650°C.

The influence of parameters such as the heating rate during sintering and the substrate’s etching treatment on the films quality was studied. The films were characterized by X-ray diffraction, SEM, and UV-Vis spectrophotometry. We observed that the heating rate is an essential parameter to obtain a homogeneous layer. The optical response and photoelectrochemical behavior were studied as function of the film thickness. We show that the material is capable of reducing water under sunlight.

[1] L. Wei, C. Shifu, Z. Sujuan, Z. Wei, Z. Huaye, Y. Xiaoling, Journal of Nanoparticle Research 2010, 12, 1355-1366.
Electronic Structure and Optical Properties of Nb2O5 Photo-Catalyst Calculated By Density Functional Method
Authors: Shirvanian Pezhman , Hao Michael
Published: February 2020

Recently, there has been attempts to increase the photo-catalytic activities of Nb2O5 with the addition of carbon modifications [1-4]. It has been proposed that carbonate species on the modified Nb2O5 act as surface sensitizer, which extends the photo-catalytically active region of Nb2O5 into the visible range [1-3]. Experiments have shown the photo-catalytic activity of these carbon-modified Nb2O5 structures are higher than of non-carbon-modified Nb2O5 and carbon-modified meso-porous TiO2 [1]. These carbon-modified Nb2O5 structures are promising candidates for photo-catalytic water splitting and more research is needed to understand these materials at the atomic scale. Here, we propose a DFT study of carbon-modified Nb2O5 (001) plane. The aim of this study is to determine the source of activity gain through electronic structure calculations. First, ground state, density of states, energy band structures, and optical properties of carbon-modified Nb2O5 are calculated. The electronic interaction between carbon and Nb2O5 will also be examined to determine its contribution to modify adsorption of intermediate species such as O2, H2, and OH. Band edge potentials and band gaps as calculated indicate the potential for driving the water cleavage reaction using solar energy. These results as presented point to a set of design guidelines for optimizations of photo-catalytic activity of Nb2O5.

  References

 1. Ge, S., Jia, H., Zhao, H., Zheng, Z., & Zhang, L. (2010). First observation of visible light photo-catalytic activity of carbon modified Nb2O5 nanostructures. Journal of Materials Chemistry, Journal of Materials Chemistry, 20, 3052-3058.

 2.Ma, Chen, Li, Cui, & Lin. (2015). Annealing-free synthesis of carbonaceous Nb2O5 microspheres by flame thermal method and enhanced photo-catalytic activity for hydrogen evolution. Materials Research Bulletin, 66, 51-58.

 3. Qi, S., Fei, L., Zuo, R., Wang, Y., & Wu, Y. (2014). Graphene nano-cluster decorated niobium oxide nanofibers for visible light photo-catalytic applications. Journal of Materials Chemistry A, 2(22), 8190-8195.

 4. Li, L., Deng, J., Yu, R., Chen, J., Wang, Z., & Xing, X. (2013). Niobium pentoxide hollow   nanospheres with enhanced visible light photo-catalytic activity. Journal of Materials Chemistry A, 1(38), 11894-11900.
(Invited) Personalized Breath-Based Health Monitors
Authors: Gouma Pelagia
Published: February 2020

This talk will highlight the research and development efforts of my team towards

the personalized diagnostic breathalyzer to be used for the detection and monitoring

of diseases or metabolic malfunctions, both in humans and in livestock. Based on the

principle of selective chemosensing, nanostructured, gas-selective probes have been

developed which detect disease-signaling biomarkers in a single exhale. Such probes include:

NO sensor for asthma monitoring; acetone sensor for the control of treatment in diabetics;

ammonia for determining the end-point in hemodialysis, etc. These sensing probes, whether

individually or in arrays, constitute components of sensory systems that are inexpensive,

handheld, wireless, and low power. The pathway and timeline from lab-based prototyping

to industrial scale manufacturing of this technology are also discussed here.
Synthesis and Characterization of Nanoporous SnO2 Thin Film
Authors: Jiang Wufeng , Hao Su-ju , Zhang Yu-zhu , Ling Yunhan
Published: February 2020

SnO2 is a kind of typical n-type semiconductor material. Due to its excellent performance in conductivity, optics, thermal stability and corrosion resisting, it has been widely applied in fields of gas sensor, solar cell, chemical electrode materials. A novel synthesis route, originated from dealloying of Sn-Zn alloys films in hydrochloric acid (HCl) solution and then thermal treating, has been developed for the preparation of SnO2 films with three-demensional (3D) nanoporous. The influences of the HCl solution concentration and immersion time on crystal structure and morphology have been investigated. Porous structure and fracture surface morphology of the samples were characterized by field emission scanning electron microscopy (FE-SEM), energy dispersive X-ray spectroscopy (EDS) and X-ray diffraction (XRD). The results indicated that the corrosion weight loss of Zn increased with the increasing of immersion time in HCl solution。An average pore diameter of the porous SnO2 films is 50~200nm after heat treatment at 500°C for 2 hours. XRD patterns show that the films are SnO2 with rutile structure.
Plasmonic Gold Nanohole Arrays for Surface-Enhanced Raman Scattering Biosensing
Authors: Zheng Peng , Gao Xuefei , Wu Nianqiang
Published: February 2020

Gold nanohole arrays can serve as promising substrates for construction of surface-enhanced Raman scattering (SERS) biosensors. Gold nanohole arrays support tunable localized surface plasmon resonance (LSPR) and propagating surface plasmon polariton (SPP). However, it is a great challenge to optimize their performance due to coexistence of LSPR and SPP. Here, finite difference time domain (FDTD) simulation is used in combination with measured transmission and reflection to discern which resonance mode leads to the electromagnetic field enhancement. The SERS peak signal intensity has been mapped with the nanohole size, which shows that the “gap” between neighboring nanoholes in the array pattern and the absorption play an important role in SERS enhancement. Optimization of hole size and pitch is necessary for development of nanohole array based SERS biosensors.
Preparation of Glucose Oxidase-Immobilized Electrodes Using Cellulose Aqueous Solution
Authors: Yasuzawa Mikito , Omura Yuya , Hiura Kentaro , Li Jiang , Fuchiwaki Yusuke , Tanaka Masato
Published: February 2020

Nearly transparent cellulose aqueous solution was prepared using the clear layer of diluted cellulose dispersion solution produced by wet jet milling. Glucose oxidase (GOx) was immobilized on platinum-iridium electrode by applying certain amount of cellulose aqueous solution containing GOx and dried for at least two days in room temperature.  The obtained GOx-immobilized electrodes provided good response current up to 22.4 mM.  Good linear relationship between glucose concentration and response current was observed.  Correlation coefficient of 0.994 was obtained ranging from 0 to 11 mM on the electrode prepared using 500 mg/L cellulose and 250 mg/L GOx mixture solution.  The sensor response was significantly fast and steady state current was obtained within one second. The stability of GOx-immobilized electrode response was measured for 30 days. After initial decrease of response current for the first few days, relatively constant responses were obtained for twenty days.
Oligopeptide Probe Coated Magnetoelastic Biosensors for the Rapid Detection of Salmonella Typhimurium
Authors: Suh Sang-Jin
Published: February 2020

Magnetoelastic (ME) biosensors are composed of a resonating platform upon which molecular recognition probes are coated to capture and bind with a target species. Previously, we developed methods to isolate highly selective phage-displayed oligopeptide probes and immobilize them upon ME sensor platforms. These methods were used to isolate highly selective Salmonella enterica serovar Typhimurium probes that do not bind to other serovars of pathogenic Salmonella. The probes were tagged with Strep II tag before affinity immobilization upon a streptavidin coated ME sensor platform. The limits of detection were determined by testing over the range of 102 to 106 cells and these ME biosensors were found to have greater sensitivity than other ME biosensors coated with E2 phage. The ME biosensors coated with oligopeptide probes were found to be highly selective for S. Typhimurium and did not react with S. Enteritidis, S. Newport, or E. coli O157:H7. These results demonstrate the efficacy of the ME biosensor method to detect S. Typhimurium and validate our approach to improve the sensitivity and selectivity of the sensor. The techniques developed in this work can be easily adapted for any foodborne or other agriculturally important bacterial pathogens.
Layer-By-Layer Assembled Carbon Nanotube Immobilized Enzyme Cascade for Sucrose/O2 Biofuel Cell Utilization
Authors: Zhang Yuanyuan , Arugula Mary , Williams Shannon , Simonian Aleksandr
Published: February 2020

A layer by layer (LbL) assemble technique for the first time was employed to modify glassy carbon electrode (GCE) and screen printed electrode (SPE) utilizing multiwalled carbon nanotube (MWCNTs) based polyelectrolytes and enzyme cascade to facilitate efficient electron transfer in Sucrose/O2 biofuel cell. Previously, our group demonstrated layer-by-layer (LbL) assembly in fabrication of carbon nanotube (CNT) immobilized multi-enzyme biosensors for discriminative detection of multiple analytes. In this study, electrostatically interacted CNT-Invertase (INV), CNT-glucose dehydrogenase (GDH, NAD+-dependent) with cushioning bilayers CNT-polyethyleneimine (PEI) and CNT-DNA were alternatively assembled in LbL fashion on SPE (0.2 cm2) and GCE (0.07065 cm2). [Ni(phendion)(phen)]Cl2 complex and methylene green (MG) were investigated as redox mediator for electrocatalytic oxidation of NADH at reduced overpotentials. The LbL architecture showed advantages for sequential enzymatic reaction that favored the efficient penetration of substrate and products in a cascade system while MWCNT facilitated the direct electron transfer from sucrose oxidation and enhancement of the current density. With GCE as modified bioanode using MG and Ni complex, the biofuel cell produced a higher power density (μW/cm2) with 134.4% and 34.3% enhancement comparing with SPE bioanode, respectively. With Ni complex compared modified on GCE and SPE, the biofuel cell produced a higher power density (μW/cm2) with 16.6% and 101.9 % higher comparing with MG modified on GCE and SPE, respectively. The LbL assembly showed great feasibility as a simple and efficient way to construct controlled CNT-multi-enzyme modified electrodes for biofuel cell applications.
The Dynamic Characterization of Electrochemical Proximity Assay with a Multi-Parametric/Multimodal Spectroscopy Apparatus
Authors: Zhou Lang , Arugula Mary , Easley Christopher J , Shannon Curtis , Simonian Aleksandr
Published: February 2020

Here, a novel Multi-Parametric/Multimodal Spectroscopy Apparatus (MPMS) is designed to characterize the dynamics in the process of molecular interactions at interfaces, which integrates several synergistic surface characterization spectroscopic methods such as surface plasmon, fluorescence, and electrochemistry into one new surface analytics. Electrochemical Proximity Assay (ECPA) is used here to demonstrate novel apparatus capabilities. ECPA is a flexible method with high potential for quantitation of a variety of proteins in clinical laboratory settings or at the point-of-care. Since this method was only recently developed, there is much to learn about mechanisms of action and dynamics of sensor and/or protein recognition. In the process of ECPA, the target protein is detected via antibody DNA strands tagged with fluorescence dye or an electrochemical label such as methylene blue, so that during the dynamic binding the SPR can generate signal upon assembly of each step. Furthermore, surface fluorescence is only changed upon assembly of the labelled DNA strand, while electrochemical signal is only observed upon binding of the methylene blue (MB) labelled DNA strand. In this way, the SPR signal will thus give a non-biased view of all steps of assembly, with simultaneous fluorescence to label and monitor specific portions, and electrochemistry to allow high sensitivity and quantitative characterization of surface coverage. Therefore, the MPMS system will allow an unprecedented level of fundamental understanding of the dynamics of the ECPA process. With increasing interest in functional interfaces, it becomes increasingly important to characterize chemical structures and biomolecules on surfaces in a quantitative fashion, and to test their proper allocation orientation, conformation, activities, stability, etc. This newly developed MPMS system can overcome several key limitations of current, widely-used surface characterization technology, and facilitate new quantitative insights into the interactions of a broad range of chemical and biological species with rationally designed interfaces.

Figure 1
Development of on-Site Applicable Immunosensor Combined with Light Microscopic Imaging System for the Detection of Salmonella in Poultry
Authors: Oh Jun-Hyun , Park Mi-Kyung
Published: February 2020

The common sources of Salmonella outbreak are poultry and poultry products, meat and meat products, and eggs.  Despite extensive efforts to reduce Salmonella outbreaks, it is almost impossible to eliminate all the possible chances of Salmonella contamination.  Thus, the best prevention strategy is to monitor and detect Salmonella using rapid, sensitive, specific, and simple detection methods.  The objective of this study was to demonstrate the feasibility of the on-site applicable immunosensor combined with a light microscopic imaging system (LMIS) for the detection of Salmonella in chicken.

Since the selection of antibodies as a bio-recognition element is the most critical factor for the performance of the biosensor, the anti-Salmonella polyclonal antibodies (pAbs) were produced and purified.  The reactivity and specificity of purified anti-Salmonella pAbs were compared with those of commercial anti-Salmonella pAbs using an indirect ELISA.  The gold sensor platforms were modified with dithiobis-succinimidyl propionate (DSP) to enhance the immobilization of antibodies.  The schematic diagram for general preparation of immune sensor combined with LMIS is presented in Figure 1.  After the optimum concentration of antibody was determined, the immobilization of the antibody was confirmed using an atomic force microscope (AFM).  The detection limit of the developed immunosensor was determined by applying the sensor to detect Salmonella in chicken skin. 

Our results showed that there was no significant difference in the reactivity between the purified anti-Salmonella pAbs and commercial anti-Salmonella pAbs over the entire range of concentrations used.  The purified anti-Salmonella pAbs exhibited not only excellent specificity against 11 non-Salmonella strains but also excellent reactivity towards 20 other non-Salmonella serovars.  The optimal concentration of antibody for immobilization on the sensor was determined to be 100 μg/mL.  The AFM images confirmed the binding of the antibody on the sensor by providing irregular and globular surface features.  The detected number of Salmonella on the immunosensor was proportional to the concentrations of inoculated Salmonella numbers when the sensor was applied to chicken.  The number of detected Salmonella significantly increased throughout the inoculated concentration ranges of 104–108 cfu/chicken with a 100% positive rate (p < 0.05).  The detection limit and time of the detection method were determined to be 103 cfu/sensor and within 1 h, respectively.  With the advantage of direct observation and enumeration of Salmonella on the immunosensor, the developed immunosensor combined with LMIS could be used to detect Salmonella in chicken as a specific, sensitive, simple, and practical detection method.

Figure 1
Enhanced Pathogen Detection on Fresh Produce Using Micron-Scale Magnetoelastic Biosensors
Authors: Horikawa Shin , Chai Yating , Wikle Howard Clyde , Suh Sang-Jin , Barbaree James M , Chin Bryan A
Published: February 2020

Phage-immobilized magnetoelastic (ME) biosensors have proven promising in detecting food surface contamination rapidly and inexpensively. These biosensors are wireless, mass-sensitive biosensors and can be placed directly on food surfaces to detect the presence of target pathogens. Previously, millimeter-scale strip-shaped ME biosensors have been used to demonstrate direct detection of Salmonella Typhimurium on various fresh produce surfaces, including tomatoes, apples, shell eggs, and watermelons. Since the biosensor must come into direct contact with Salmonella bacteria, food surfaces with large roughness and curvatures (e.g., leafy green vegetables) may allow the bacteria to avoid direct contact, thereby avoiding detection. Hence, the primary goal of this paper is to investigate the effects of food surface topography and sensor size on the detection capabilities of the biosensors. Spinach leaf surfaces were selected as model surfaces, and detection experiments were conducted with differently sized micron-scale biosensors. Spinach leaf roughness and curvatures of both adaxial (topside) and abaxial (underside) surfaces were measured using a laser confocal microscope. The experimental results showed that in spinach as the sensor is made smaller, the physical contact between the biosensors and bacteria are improved. Smaller sensors thereby enhance detection capabilities. When proper numbers of biosensors were used, micron-scale biosensors were found to yield improved limits of detection over previously investigated millimeter-scale biosensors.
Novel Magnetostrictive Fe-Co-B Thin Film Sensors for Food Safety Detection
Authors: Sheng Zhizhi , Cheng Z.-Y.
Published: February 2020

As a soft magnetic material with amorphous or nanocrystalline structure, magnetostrictive Fe-Co-B alloy has been considered a potential candidate for high-frequency sensor application. For sensor behavior, high sensitivity and low limit of detection are favored. The smaller the sensor is, the higher the sensitivity it has and the higher the frequency it can achieve. To obtain higher sensitivity, micro scale Fe-Co-B sensors are fabricated with electrochemical deposition and microfabrication. Free-standing Fe-Co-B sensors with a sandwich structure of Au(410 nm)/Fe55Co28B17/Au(130 nm) and an area of 500 μm×100 μm are synthesized. The thickness of the sensors are around 2~10 μm. The magnetostrictive particles show good resonance behavior.  The resonance frequency is about 3 MHz and Q value can be up to 200 in air. The influence of the current density and deposition time on the resonance behavior are investigated. Au/Fe55Co28B17/Au sensor is used to detect Salmonella Typhimurium in dynamic bacteria suspensions. For a 500 μm×100 μm× 7 μm sensor, a limit of detection of 5×102 cfu/ml is achieved with a total peak shift of 103 kHz which are comparable to reported commercial materials. It is very promising to dig out the important role of Fe-Co-B alloy in high-frequency sensors or other micro electronics.
Microelectrochemical Property of Precipitates in Al-Mg Alloy
Authors: Sakaizawa Yuto , Muto Izumi , Oya Yoshiyuki , Koyama Takahiro , Sugawara Yu , Hara Nobuyoshi
Published: February 2020

Al-Mg alloys are widely used for many applications, such as marine and land vehicles, construction industry, and chemical plants. Mg is added to Al to strengthen via solid solution hardening and to improve corrosion resistance. However, β phases (Al3Mg2) precipitates along grain boundaries after heat-treatment at elevated temperatures from 323 K to 573 K, and several kind of precipitates also exist in Al-Mg alloys. Localized corrosion is thought to be caused by local cell between the matrix and the precipitates. It is important to analyze the microelectrochemical property of precipitates and the matrix. And also, corrosion initiation mechanism is still unclear. In this research, microelectrochemical measurements were carried out to observe initiation site and growth of pitting.

Specimen was AA5182 alloy. The chemical composition was shown in Table 1. No heat treatment was performed in this study. At first, the characterization of the precipitates on the specimen was conducted. Precipitates were classified into two types (Types A and B) by optical microscopic observation of the polished surface using Ar+ ion milling. The colors of Types A and B were blue and gray, respectively. From the result of energy dispersive X-ray analysis (EDS), Types A and B were determined to be Mg2Si and Fe-rich intermetallic. To ascertain the existence of β phase, the specimens were immersed in 40 mass% H3PO4for 180 s. No selective dissolution along grain boundaries was observed. It was considered that β phase did not precipitated in as-received conditions (mill-annealed).

Microscopic potentiodynamic polarization was performed in a naturally aerated 0.1 M NaCl solution at 298 K to observe initiation site and growth of pitting. The sample was mechanically ground with SiC paper through a 4000 grit, and then polished down to 1 µm using diamond paste. Electrode area was about 0.1 mm2. Fig.1 (a) shows the microscopic polarization curve. Several current spikes were generated during the polarization, and these were thought to be related to pit initiation. Fig. 1 (b) exhibits an image of the electrode area by scanning electron microscope (SEM). As shown in Fig. 2 (a) and (b), initiation site of stable pit was related to the precipitate. Other dissolution sites were also observed: Mg2Si became Si-oxide by selective dissolution of Mg, and the matrix around Fe-rich intermetallic dissolved since the intermetallic became cathodic site.

Figure 1
Fabrication By Electrodeposition of a New Tin Anode Reinforced with Carbon Nanotubes for Lithium Ion Batteries
Authors: Matsunaga Kouki , Arai Susumu
Published: February 2020

Introduction

Lithium ion batteries using graphite as the anode active material have higher energy densities than conventional rechargeable batteries, but obtaining higher capacity will require use of an alternative anode material. Tin has a higher capacity than graphite (991 mAh g-1 vs. 372 mAh g-1) and was used in the current research as an active material. However, tin slips down from the current collector during charging and discharging due to a large volume change, and the cycling characteristics deteriorate. Anchoring the tin layer to the underlying copper layer with a fibrous material should improve adhesion. We previously demonstrated the excellent charge/discharge characteristics of a new tin anode comprising an electroless tin plating film deposited on a Cu/CNT (carbon nanotube) composite plating film.1)

In this study, we created a new negative electrode structure incorporating CNTs by electrodeposition and explored the correlation between the structure and charge/discharge characteristics of the electrode.

Experimental

A Cu/CNT composite plating bath (0.85 M CuSO4・5H2O + 0.55 M H2SO4 + CNTs + polyacrylic acid) and a tin plating bath (1 M K4P2O7 + 0.25 M Sn2P2O7 + additive) were prepared. Cu/CNT composite plating film was plated on a pure copper plate, then tin was electrodeposited on the Cu/CNT composite plating film, generating a new CNT-reinforced tin anode structure. For comparison, tin was electrodeposited directly on a pure copper plate. Electroplating was carried out under galvanostatic conditions at 25°C. The Cu/CNT composite plating film on a pure copper plate and a platinum plate were used as the cathode and anode, respectively, for tin plating.

The microstructure of the new tin anode was examined by field-emission scanning electron microscopy (FE-SEM). The phase structures of the deposits were analyzed by X-ray diffraction (XRD).

Electrochemical studies of the tin-based anodes were carried out using coin cells assembled in an Ar-filled glove box. Each coin cell consisted of lithium foil as the counter and reference electrodes and the tin-based anode as the working electrode. The electrolyte was 1 M LiPF6 in ethylene carbonate (EC) and diethyl carbonate (DEC) (1:1 vol%). Cycling tests were performed in the range 0.02 - 1.5 V (vs. Li/Li+) at a constant temperature of 25°C.

Results and Discussion

Fig. 1 shows a surface SEM image of the new tin anode and demonstrates that tin particles had deposited on the CNTs. Fig. 2 shows a cross-sectional SEM image of the new tin anode; CNTs are clearly seen between the tin and copper layers, and no defects are observed.

The charge/discharge characteristics of the new tin anode will be discussed at the meeting.

References

1)         R. Fukuoka, S. Arai, Abstract of the 44th Annual Meeting of Union of Chemistry-Related Societies in Chubu Area of Japan, 133(2013)

Figure 1
In Situ Observation of Electrodeposition of Li on Pt and Ni Substrates in Organic Electrolyte
Authors: Munemura Naoaki , Muto Izumi , Sugawara Yu , Hara Nobuyoshi
Published: February 2020

Li metal has attracted attention as a material of negative electrodes for rechargeable batteries, but has the problem of reversibility due to Li dendrite formation during charge-discharge cycles. The suppression of Li dendrite formation is essential for developing Li metal rechargeable batteries. The morphology of electrodeposited Li and the growth of Li dendrite have been studied extensively; however, the relationship between the growth of Li dendrite and the change of electrochemical signal is still unclear. To clarify this relationship, it is necessary to conduct in situ optical microscopic observation.

To investigate the effect of current density on Li deposition morphology, potentiodynamic and galvanostatic polarization measurements were conducted. Pt and Ni substrates were mechanically polished with SiC paper through 1500 grit, and then polished down to 1 µm using diamond paste. The counter electrode was a Pt wire. The reference electrode was Li. 1 M LiPF6 EC:DMC(1:1 vol%) was used as the electrolyte. The electrode surface area was around 95mm2. The current density for the galvanostatic experiment was varied from 0.1 to 2.0 mA/cm2, and the electrochemical deposition of Li was performed at constant charge (3.6 C/cm2). Surface observations were conducted by an optical microscope and a laser microscope. All electrochemical measurements were carried out in a glove box filled with argon.

Figure 1 shows the cathodic polarization curves of Pt and Ni substrate. The increases in cathodic current densities were observed at around 0 V(vs.Li/Li+), indicating that the electrodeposition of Li proceeded at the potential range less than 0 V. Figure 2 shows the laser microscope images of the electrode surfaces after the galvanostatic polarization measurements. The surface of Li deposited on Ni was smooth compared with that on Pt. In particular, non-uniform deposition was observed at 0.1 and 2.0 mA/cm2 on the Pt substrate. In the case of the Ni substrate, a more uniform deposition was observed at lower current density.

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Bipolar Membrane Fabrication for Fuel Cells
Authors: Ahlfield John M. , Liu Lisha , Kohl Paul A
Published: February 2020

Bipolar membranes fuel cells utilizing both anion and cation conductive materials have several advantages compared to their purely acidic or alkaline counterparts due to improved water management and electrode kinetics. Material transport properties play an important role in determining viability of membrane and ionomer materials. Additionally, the material at the cation/anion junction is critical to device performance, as it must conduct ions to the interface in addition to mechanically binding the membranes. A series of devices using different interfacial materials has been fabricated for use in direct methanol and hydrogen fuel cells. These fuel cells were characterized by performance metrics and electrochemical impedance spectroscopy to determine specific areas for improvement in the bipolar devices. In this manner, the effect of the cation/anion junction location can be determined and used for further improvement of bipolar membrane fuel cells.

Financial support from US Office of the Deputy Assistant Secretary of the Army for Defense Exports and Cooperation (DASA-DE&C) is gratefully acknowledged.
Carbon Dioxide Absorption Behavior and Carbonate Ion Transport of Lithium Orthosilicate / Potassium Carbonate Coexistence System Prepared By Ball Milling
Authors: Kanki Kyohei , Maki Hideshi , Mizuhata Minoru
Published: February 2020

Lithium Orthosilicate (Li4SiO4), a type of ceramic CO2 absorbent has a large absorptive capacity (36.7 wt. %) and also has heat resistance. This material has some useful application as a separator in Molten Carbonate Fuel Cell and as a direct CO2 absorbent in large-scale emission sources, for example, thermal power stations; because the following equilibrium reaction at the temperature around 993 K; Li4SiO4 + CO2  ⇄  Li2CO3 + Li2SiO3. In this study, we focused on the absorption behaviors of CO2 at lower temperature into Li4SiO4 in combination of these two methods and evaluated the physiochemical dependence of surface properties of CO2 absorption reaction.

Li4SiO4 was prepared from solid state reaction. SiO2 powder and Li2CO3 powder were mixed at the molar ratio Li/Si = 4.0. The mixture was calcined at 973 K for 20 h in air. The resulting powder (Li4SiO4) kept in an Argon atmosphere glove box and in order to confirm the effect of carbonate, was mixed with a given amount of K2CO3. Each mixture (2.5 g) was put in the grinding bowl with the grinding balls, it sealed up under the Ar atmosphere, and the grinding processing was done for 0-300 minutes in revolution speed 250 rpm using planetary ball mill.              Also, the grinding process was done under the condition of one cycle for 15 minutes of the grinding processing and two minutes of rest time to prevent the samples temperature from rising. Samples were characterized with X-ray diffraction (XRD), N2-isotherm, SEM, SEM-EDX, TG-DTA and Electro spin resonance (ESR).

It was found that samples whose surface was modified with ball milling method under Ar gas flow showed a tendency to increase the surface area estimated by BET method measured by N2-isotherm and increase of Si dangling bond measured by ESR. Also, it was found that there are two different absorption processes, one is a chemisorption at the surface (T<773 K) the other is a bulk diffusion (T>773 K) by the result of TG-DTA. As seen in isothermal analysis (Fig. 1), the CO2 absorb reaction rate improved by the coexistence of K2CO3 infiltrated in Li4SiO4 being promoted by not only the surface area was increased and activated by the ball milling but also absorbing CO2 of coexisting K2CO3. Furthermore, it was found that ΔG‡
decreased from the result of the isothermal analysis at 873 K. We would like to consider controlling transportation of carbonate ion electrochemically according to the CO2 absorption reaction as a separator in Molten Carbonate Fuel Cell.

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Studies of Electrode/Electrolyte Interfaces
Authors: Parr Daniel , Chrestenson Jacob , Malik Kasim , Haverhals Luke M.
Published: February 2020

The utilization of ionic liquids (ILs) for future electrochemical applications shows great promise.  Recently ILs have been investigated for many electrochemical systems however, further characterization and development of ILs remains to be accomplished before they are applied to devices such as batteries, capacitors, and fuel cells.  For example, data that yield understanding of the interfacial structure and dynamics of ILs at electrode surfaces are vital since these interactions ultimately allude to electrochemical device efficiency.  We will present data from time resolved (TRS) FTIR spectroscopy coupled with cyclic voltammetry as a means to characterize interfaces between IL-based electrolytes and metal electrode surfaces.
Cyclic Voltammetric Analysis of 1-Methyl-4-Nitroimidazole Under Biological Conditions
Authors: Nguyen Andrew Doan , Darzi Ghazwan M , Smith Diane K.
Published: February 2020

Nitroimidazoles are biologically active compounds that also have medicinal uses. 5-Nitroimidazoles are currently used as anti-bacterial drugs and a 2-nitroimidazole is used to treat Chagas disease. The nitroso and hydroxylamine, which are reduced forms of nitroimidazoles, are believed to be the active anti-bacterial agents. Compared to the 2- and 5-nitroimidazoles, 4-nitroimidazoles are known to be inactive under biological conditions. In this project cyclic voltammetric analysis of a simple 4-nitroimidazole, 1-methyl-4-nitroimidazole, is currently being run to analyze the stability of its reduction products under biological conditions and their reactivity with cysteine. Previous studies of the 4-nitroimidazole have been done in DMSO with cysteine additions because it is believed that the reaction of nitroimidazole with cysteine is the likely cause of cell death in bacterial species. The cyclic voltammetric analysis between the 2-, 4-, and 5-nitroimidazoles in DMSO with cysteine additions yielded similar trends of reduction and oxidation potential. Between the 4- and the 5-nitroimidazoles, the 4-nitroimidazole is shown to have a more negative reduction potential than the 5-nitroimidazole. This difference in reduction potential might be the cause of the 4-nitroimidazole inactivity under biological conditions. Currently the 4-nitroimidazole is being analyzed under aqueous conditions with cysteine additions. This change from DMSO to an aqueous solution allows for further analysis of the compound under biological conditions.
A New Class of Stable Electrolytes Based on "Hindered Glymes" to Prevent Graphite Exfoliation in Lithium Secondary Batteries
Authors: Shanmukaraj Devaraj , Grugeon Sylvie , Laruelle Stephane , Armand Michel
Published: February 2020

Safety of lithium batteries is one of the major hurdle for their further development in all the fields of electrical energy storage, especially electric transportation. Commercial lithium batteries use as electrolytes, mixtures of at least one cyclic carbonate, the most common of which is ethylene carbonate (EC) to which various proportions of propylene carbonate (PC) can be optionally added. They are necessary to dissociate the lithium salt used as solute, as they are highly polar (ε > 60).  Since such cyclic carbonates are either solid (EC) at room temperature, or highly viscous (PC), co-solvents or thinners are usually added, the most common of which are dimethyl carbonate (DMC), diethyl carbonate (DEC) and ethyl-methylcarbonate (EMC). The solutes containing in the electrolyte compositions are usually selected from lithium salts with low lattice energy like LiBF4, LiCF3SO3, Li[CF3SO2)2N], LiPF6. In practice, LiPF6 is almost exclusively used because of its high conductivity and beside does not corrodes aluminum, the current collector, at potentials up to 4.5 V vs Li+:Li°.The linear components (DMC, DEC, EMC) acting mainly as a diluent of  high-melting EC, are however the least stable component and have low flash points that are serious handicaps for lifetime and safety. It thus makes it a critical requisite to reconsider the choice of the electrolyte, especially trying to get rid of the alkyl carbonate, fragile to reduction (RO-, RCO2
•) [1], and with low flash points (dimethyl carbonate, DMC, Fp = 17 °C). On the other hand, poly ethers are a good alternative, Moreover ethers [2, 3] are also easily biodegradable solvents that are very stable to reduction and anodically withstand up to 3.9 V, suitable for the LiFePO4 electrode but all formerly known representatives solvates Li+ strongly enough to co-intercalate in the graphite negative electrode and exfoliate it.

We have put forward a new electrolyte composition comprising a polyether to which a bulky Tert-butyl group is appended (“hindered glyme”), totally preventing co-intercalation while keeping good conductivity. This alkyl carbonate-free electrolyte shows remarkable cycle efficiency of the graphite electrode, not only at RT, but also at 50 and 70°C with lithium bis(fluorosulfonimide) salt. The two-ethylene bridge “hindered glyme” has higher boiling point and a flash point of 80°C, a considerable advantage for safety.

Reference:

1. D. Aurbach, B. Markovsky, I. Weissman, E. Levi, Y. Ein-Eli,  Electrochim. Acta  1999, 45(1-2), 67-86.

2. D. Aurbach, E. Granot, Electrochim. Acta  1997, 42(4), 697-718.

3. S. Tobishima, H. Morimoto, M. Aoki, Y. Saito, T. Inose, T. Fukumoto, T. Kuryu, Electrochim.
Acta  2004, 49(6), 979-978.

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