bluuebunny/crossref_metadata_2025 huggingface dataset:
Optimization of Microelectrode Cholesterol Efflux Measurements By Platinum Crystallites on Carbon
Authors: Burgess Jim , Li Li
Published: February 2020

Cholesterol efflux from the cell plasma membrane is known to be increased in cell-line and mouse models of cystic fibrosis.  A noninvasive means of characterizing plasma membrane cholesterol efflux at affected tissues is needed to extend the trends found models of cystic fibrosis to humans suffering from the disease.  Microelectrode induced cholesterol efflux from the plasma membrane surface of tissue is proposed as a strategy to demonstrate increased cholesterol efflux for cystic fibrosis in human subjects.  Demonstration for electrochemical sensor detection of cholesterol efflux from the human buccel mucosa has been accomplished by this research group.  Using a pulsed potential scheme for detection of hydrogen peroxide, cholesterol oxidase modified platinum microelectrodes show proof-of-concept for the in vivo diagnostic assay.  Increased signal has been achieved using carbon microelectrodes containing electrodeposited platinum crystallites.  Additional optimization of the sensor is being explored by synthesizing platinum crystallites in solution for subsequent deposition on the carbon microelectrode.  The aim is to improve repeatability of sensor fabrication by better controlling the size, shape, and distribution of platinum crystallites deposited on the carbon microelectrode surface.
DNA Films As Sensing Platforms for Detection of DNA Damage Induced By Peroxynitrite
Authors: Salim Heba azmy , Bayachou Mekki
Published: February 2020

Genetic characteristics are determined by DNA in living beings. Many chemical and physical effects can cause damaging for DNA molecules which may ends up with various pathogenic conditions. Peroxynitrite (ONOO−) is one of these chemical agents that damage DNA.

 ONOO− is a strong oxidizing and nitrating agent that correlated with many pathological conditions. It forms in-vivo through fast reaction between nitric oxide and superoxide in various pathological conditions. For example, ONOO− leads to generation of reactive oxygen species (ROS) in human leukemia cells. Additionally, in acute and chronic inflammation, ONOO− generates as a highly reactive species that causes oxidation, nitration for protein, DNA bases modification, and DNA strand breaks. DNA damage frequently leads to chromosome aberrations and mitotic faults. Accumulation of mutations and/or other kinds of DNA damage represent carcinogenic or teratogenic risk. Development of analytical techniques capable of rapid and sensitive detection of various types of DNA damage and DNA damaging agents is therefore our research focus.

In our work, we detect ONOO− damaging effect using DNA films as a sensing platforms. Two methods have been used for DNA immobilization on the electrodes surfaces; grafting and layer-by-layer (LBL) methods. The former method is based on grafting glassy carbon electrode surface with carboxylic acid groups via electrochemical reduction of trans-4cinnamic acid diazonium tetrafluroborate followed by coupling of pre activated carboxylic groups with amino terminated oligonucleotide. While the LBL technique is based on depositing Poly(diallyldimethylammonium) (PDDA), a positively charged polyelectrolyte, and DNA as a negatively charged counterpart macromolecule on the surface of graphite electrode. Chronocoulometry, cyclic voltammetry, and square wave voltammetry have been used to detect the DNA damage induced by peroxynitrite through defined electrocatalytic processes. This is done through investigation of the electrochemical behavior of DNA biosensors before and after their exposure to peroxynitrite.
Rapid Thermal Annealing in MgO Sensing EIS Membrane for Bio-Sensor Applications
Authors: Lin Chun-Fu
Published: February 2020

We tried to find an alternative dielectric film to own the high quality sensitive properties, so that, magnesium oxide (MgO) has been selected as a pH sensitive dielectric for the EIS operation, and is known as an alternative gate dielectric as CMOS technology has aggressively scaled down.The high-k MgO as sensing membrane on EIS structure and to investigated the characteristics of the different rapid thermal annealing(RTA) temperature in oxygen ambient. Furthermore, we studied the sensing performance of the MgO EIS structure tested in different ion (H+,Na+, K+, Urea, Glucose) solution.

The electrolyte-insulator-semiconductor (EIS) structures with MgO sensing membranes were fabricated on 4-inch n-type (100) Si wafer, which have a resistivity of 5–10 Ω-cm. Before deposition of the MgO film, the wafers were cleaned by using HF-dip (HF: H2O = 1:100) to remove the native oxide. Then, a 50-nm MgO was deposited by radio frequency (RF) reactive sputtering on n-type silicon wafer. During RF sputtering, Mg oxide-target was used with 25 sccm argon flow rate (Ar: O2=25:0). The (RF) power and pressure are 150Watt and 20mTorr, respectively. Next, Samples was annealed at different temperatures (600oC, 700oC, 800oC) by rapid thermal annealing (RTA) in O2 ambient for 30 sec. The back-side contact of the Si wafer was deposited by Al film with 300nm-thick. Then, sensing area was defined by standard photolithography process using a photosensitive epoxy, SU8-2005 of MicroChem Inc. Finally, the samples were fabricated on the copper lines of printed circuit board (PCB) by silver gel. Epoxy package was used to separate the EIS structure and the copper line.

In this study, we report an electrolyte–insulator–semiconductor (EIS) sensor with a high-k magnesium oxide (MgO) as sensing material. The effect of rapid thermal annealing (RTA) on the deposited sensing membrane has been studied in terms of structural and sensing characteristics. We used X-ray diffraction (XRD), X-ray photoelectron spectroscopy (XPS), and atomic force microscopy (AFM) to investigate the structural and morphological characteristics of deposited films. Furthermore, we studied the sensing performance of the MgO EIS structure in different ion solutions such as Urea and Glucose solutions. EIS device with MgO as sensing membrane that has been subjected to 800 ºC RTA treatment exhibits better sensing characteristics such as sensitivity of 61.64 mV/pH, hysteresis voltage of 5.03mV and 1.55mV/hr drift rate.
Micro-Thermal Stage and Custom-Made Pt-Ir Tips for High Temperature Electrical and Electrochemical Studies By Scanning Probe Microscopy
Authors: Ng Chee Seng , Baek Jong Dae , Zade Vishal , Villegas Adrian , Su Pei-Chen , Martini Ashlie , Lee Min Hwan
Published: February 2020

Scanning Probe Microscopy (SPM) is arguably the only tool that is available for direct nanoscale electrical and electrochemical characterization since electrical measurement through a highly localized area necessitates a nanoscale electrode. However, conventional SPM systems are functional only up to ~250°C under atmospheric pressure because significant heat convection from the heating stage to thermally-sensitive system modules disturbs a stable operation1,2. In operando observations of non-vacuum processes necessitating a much higher temperature, e.g. solid oxide-based electrochemical reactions and phase changes, have been largely limited. To address these problems, we have developed micro-thermal stage (MTS)3 in which the heating element is on the micrometer scale with an area roughly a million times smaller than that of a conventional SPM heating stage. We also prepared SPM probes custom-made to suppress thermal degradation during high temperature operation. At high temperature, metal-coated SPM tips tend to degrade at a faster rate, resulting in erroneous observations. The modified SPM setup was applied to study thermally activated bonding formation and highly localized oxygen reduction reaction kinetics on a solid oxide electrolyte.

For the MTS, Pt is micro-patterned on a silicon chip as the heating element and a thin film-based layer of study are deposited on top of the heating element after electrical passivation. The temperature of the Pt heater can be determined by the measured electrical resistance of the heater because the resistance of a metal linearly increases with temperature4. A four-probe measurement scheme is integrated onto the chip for sensing the resistance and corresponding temperature of the heating element. The temperature of the heater is feedback controlled. Due to the small size of the heating element and small sample thickness, the desired temperature can be reached and controlled in milliseconds. To circumvent the degradation issue of Pt-coated tip, an all-metal tip is custom-made from Pt-Ir wire by electrochemical etching method, from which tip radii less than 100 nm can be routinely achieved. The non-etched part of the wire is flattened and polished to mount on an SPM system. After verifying the functionality of the Pt-Ir SPM tip through routine SPM contact mode scanning, we used the modified setup to study localized in-situ oxygen reduction catalysis and ionic transport on a platinum/yttria-stabilized ceria (Pt/YSZ) half cell. The aforementioned modified SPM setup has potential to be used in many other applications, such as in-situ observation of changes in mechanical, electrical and thermal properties at the tip-sample interfaces under high-temperature and high-pressure conditions.

Research supported by the AFOSR (Grant # FA9550-15-1-0256), USA and MoE AcRF Tier 2 (Grant # ARC20/14), Singapore.

Figure 1
Synthesis of Pt-Cu Nano-Octahedra and Their Enhanced Electrocatalytic Activity for Oxygen Reduction Reaction
Authors: Tian Na , Lu Bang-Au , Zhou Zhi-You , Sun Shi-Gang
Published: February 2020

The development of proton exchange membrane fuel cells (PEMFCs) is mainly limited by the high cost Pt-based electrocatalysts1
,
2. Despite progress in the development of non-noble metal electrocatalysts, Pt-based catalysts are currently the state-of-the-art electrocatalysts in practical PEMFCs.

Binary Pt-based 3d transition metals electrocatalysts (such as Pt-Co, Pt-Cu, and Pt-Ni) is a promising approach to improve the catalyst activity and reduce the Pt loading in fuel cells. Compared to other alloy elements, Cu is more stable against electrochemical oxidation than other solute metals (for example, Ni, Co), and Cu can be stabilized in the second Pt laye. Besides, Pt-Cu alloy can be used to distinguish strain effects and ligand effects3
,
4. Besides, numerous results have suggested that the {111}-terminated Pt-alloy nano-octahedra could be very promising electrocatalysts for use as the cathode of PEMFCs. However, the synthesis of most Pt-based nano-octahedra involve bulky capping agents, which are necessary to stabilize and to prevent aggregation of nanocrystals during synthesis. However, the capping agents can reduce the free accessible surface site for O2 reaction, leading to the undesirable decrease in ORR activity. While the removal of capping agents will inevitably affect the size or morphology of the particles, which in-turn alters their ORR activity. Thus, a surfactant-free synthesis of Pt-based alloys with high activity for ORR is urgent for the development of PEMFCs.

Herein, we reported the synthesis of Pt-Cu nnao-octahedra of size about 7.2 nm by a facile surfactant-free strategy, which enhances the surface exposure and their catalytic activity for ORR. In a typical synthesis of Pt-Cu octahedra, DMF was used as solvent and reducing agent, while Pt(acac)2 and Cu(acac)2 were used as precursor. Unusually, we found that low reaction temperature favors the formation of nanocrystal with (111) facets and small size. The electrochemical surface area of synthesized Pt-Cu octahedra were determined by the CO stripping. The area-specific ORR activity activity of Pt-Cu nano-octahedra was 4.25 mA cm-2 at 0.90 V, that is about 20 times higher than that of commerical Pt/C (0.2 mA cm-2). This study provides a strategic design of Pt-based efficient catalysts for fuel cells.

Acknowledgments. This work is supported by NSFC (21222310 and 21573183).

Reference:

       (1)   Bing, Y.; Liu, H.; Zhang, L.; Ghosh, D.; Zhang, J. Chem. Soc. Rev.
2010, 39, 2184.

       (2)   Porter, N. S.; Wu, H.; Quan, Z. W.; Fang, J. Y. Acc. Chem. Res.
2013, 46, 1867.

       (3)   Henry, J. B.; Maljusch, A.; Huang, M.; Schuhmann, W.; Bondarenko, A. S. ACS Catal.
2012, 2, 1457.

       (4)  Stephens, I. E. L.; Bondarenko, A. S.; Perez-Alonso, F. J.; Calle-Vallejo, F.; Bech, L.; Johansson, T. P.; Jepsen, A. K.; Frydendal, R.; Knudsen, B. P.; Rossmeisl, J.; Chorkendorff, I. J. Am. Chem. Soc.
2011, 133, 5485.
Oxide Reduction Kinetics on Platinum
Authors: Qile Geer , Harrington David A.
Published: February 2020

Pt is a widely used catalyst for fuel cells in industry, but the irreversibility of the oxygen reduction reaction (ORR) restricts its efficiency and incurs about 40% of all irreversible energy losses1. Furthermore, the dissolution of Pt degrades the catalyst and limits its lifetime. Pt oxide is known to play a role in promoting the dissolution2 and is thought to degrade the performance of the ORR. Even though studies have been done for many years, the details of the oxide structure and the mechanism of oxide formation and reduction are still not fully resolved. In the case of the kinetics, most work has been directed at the oxide formation, and the reduction kinetics have been relatively neglected. We report here kinetic studies on the Pt oxide reduction on polycrystalline Pt by cyclic voltammetry and various potential programs that combine sweep and hold periods. Differential-equation-based models were investigated to simulate the oxide reduction and estimate kinetic parameters. 

The simplest sweep-hold method involves preparing the surface with potential sweeps and then holding the potential at selected potentials. Constant potential is typically better for quantitative analysis of kinetics since the rate constants are fixed. Compared to conventional large potential steps, the sweep preparation enables the initial conditions to be closely controlled, and the double-layer charging is less. Adding different negative-going sweeps after identical sweep-hold experiments allows for study of sweep rate dependence under identical coverage and potential initial conditions, which is not the case for regular cyclic voltammetry at different sweep rates.

Most simple mechanisms are based on rate laws in which the rates and current at time t are only dependent on the coverages and potential at time t, and not on the history of how those coverages were prepared. In contrast, rates for nucleation-and-growth type mechanisms can depend on the history. Since the oxidized surface is a restructured surface, different histories may also produced different 3-D structures at the same coverage. By varying the preparation step to produce the same coverage at the same potential but with different histories, evidence was found that the reduction peak position and shape only depend on oxide coverage and potential, and not on the history.

The results are presented and modelled with a simple adsorption mechanism, which gives reasonable agreement with experiment. Refinement will use the idea that the relationship between coverage and available Pt sites may not be linear3.

References

[1] S.G. Rinaldo, W. Lee, J. Stumper and M. Eikerling, Electrocatalysis, (2014) 5:262-272.

[2] A.A. Topalov, I. Katsounaros, M. Auinger, S. Cherevko, J.C. Meier, S.O. Klemm, K.J.J Mayrhofer, Angew. Chem. Int. Ed. Engl. (2012) 51:12613–5.

[3] P.K. Dahlstrøm, D.A. Harrington and F. Seland, Electrochim. Acta, (2012) 82:550-557.
Prussian Blue Nanocubes on Reduced Graphene Oxide As a Modified Platinum Electrode for Synergistic Methanol Oxidation
Authors: Kim Kyuwon , Manivannan Shanmugam , Kang Inhak
Published: February 2020

We report a facile synthetic strategy for the in-situ growth of high-quality Prussian blue nanocubes (PBNCs) at the amine functionalized silicate sol–gel matrix (TPDT)–RGO composite via the electrostatic interaction. Subsequently, Pt nanostructures are electrodeposited onto the preformed ITO/TPDT–RGO–PB electrode to prepare the RGO/PB/Pt catalyst. The significance of the present method is that the PBNCs could be in-situ grown by inter-connecting the RGO layers, led to 3D cage-like porous nanostructure. The modified electrodes are characterized by FESEM, EDAX, XRD, XPS and electrochemical techniques. The RGO/PB/Pt catalyst exhibits the synergistic electrocatalytic activity and high stability towards the methanol oxidation. The porous nature of the TPDT and PB, and unique electron transfer mediating behavior of PB integrated with RGO in the presence of Pt nanostructures facilitated synergistic electrocatalytic activity for methanol oxidation.
Investigating High Current Densities in Ionic Liquid Mediated Electrolysis of Carbon Dioxide
Authors: Neubauer Sebastian Stefan , Krause Ralf Karl , Gudi Dirk M. , Schmid Guenter
Published: February 2020

The production of chemical feedstock out of CO2 constitutes a key role in the contemporary field of energy storage.  Importantly, CO2 is converted by means of renewable power in a single step via a direct electrocatalytic process affording high efficiencies.  Research concerning high Faraday efficiencies combined with high current densities for the carbon monoxide (CO) formation as electrolysis product represents a fast and upcoming topic.  

Recently, it was demonstrated that ionic liquids promote the CO2 reduction by lowering the overpotential and by simultaneously increasing the selectivity for CO evolution.[1]  Only a few reports focus, however, on the performance of ionic liquids at high current densities.[2]

In our own work, we probed function-selected ionic liquids in a dynamic flow cell setup including a silver gas diffusion electrode towards high current densities by overcoming CO2 transport limitations.  In this context, Faraday efficiencies of the electrolysis products as well as electrode potentials are investigated up to 200 mAcm-2 and compared to an aqueous reference electrolyte.  Beyond that, the ionic liquids’ ability to act as an inhibitor for the hydrogen evolution reaction (HER) is evaluated.  Our work is rounded off by investigations regarding the electrolytic stability of ionic liquids by employing 1H NMR spectroscopy.  We proofed stabilities of over 100 h for the electrolysis process.

[1] B. A. Rosen, A. Salehi-Khojin, M. R. Thorson, W. Zhu, D. Whipple, P. J. A. Kenis, R. I. Masel, Science 2011, 334, pp. 643-644

[2] J. Medina-Ramos, J. L. DiMeglio, J. Rosenthal, J. Am. Chem. Soc. 2014, 136, pp. 8361-8367
(Invited) Synthesis and Characterization of DNA-Inspired Organic Nanowires
Authors: Gorodetsky Alon
Published: February 2020

One-dimensional organic nanowires and nanoribbons represent idealized model systems for investigating charge transport mechanisms at molecular length scales. However, there are significant difficulties associated with the synthesis of organic nanowires and nanoribbons with precisely defined sequences, lengths, geometries, and terminal functionalities. By drawing inspiration from the structure of DNA and from automated oligonucleotide synthesis techniques, we have developed facile strategies for the covalent assembly of organic semiconductor building blocks into precisely defined one-dimensional ensembles. We have investigated the properties of these nanowires with a suite of spectroscopic, electrochemical, and computational techniques. Our findings hold significance both for fundamentally understanding nanoscale charge transport phenomena and for the development of new types of biological and molecular electronic devices.
(Invited) Microbial Fuel Cells for Wastewater Treatment - from Lab to Practice
Authors: Bretschger Orianna , Babanova Sofia , Jones Jason , Phan Tony , Carpenter Kayla , Chan Shirley , Phadke Sujal , Chen Shing
Published: February 2020

Microbial Fuel Cells (MFCs) have been intensively studied as a promising technology for energy harvesting. However, in recent years it has become apparent that electricity production from MFCs may not yield energy densities comparable to chemical fuel cells or conventional batteries - but MFCs can provide sustainable and cost-effective wastewater treatment. Conventional centralized wastewater treatment is a very costly process requiring significant infrastructure and energy input. Further, water recycling from conventional wastewater treatment plants is becoming a more acceptable method to deliver clean water in drought-stricken areas, requiring even more energy and infrastructure for disinfection and distribution. In contrast to conventional wastewater treatment technologies, MFCs enable a decentralized method for wastewater treatment, water recycling, real-time monitoring and direct control of organic removal and biomass production. In addition, direct recovery of electric energy, high quality effluents and low environmental footprints can be achieved through MFC technologies.

However, while MFCs hold tremendous promise, the practical application of MFC technology has not been realized due great challenges in cost, system stability and optimization – all necessary steps in technology scale up and commercialization. In this study various aspects of MFC technology development from lab prototypes to practical installations for wastewater treatment have been evaluated. An MFC installation consisting of twelve MFC single chamber reactors (Fig. 1) has been designed and explored under real environmental conditions. Each reactor has a rectangular shape with either one or two anodes, positioned at the top and the bottom of the MFC, and two gas-diffusion cathodes. The installation operates under flow through mode with swine waste used as the inoculum source (along with lagoon sediment) and feed solution.

In terms of accelerated organics removal, various aspects have been addresses related to reactor design, electrode optimization, operational characteristics, cathode biofouling, biofilm development and bacterial enrichment at the anode. Each of the design aspects has been evaluated first in the lab and then transferred to the field for validation. A start up time of 5 days has been achieved with 0.55 V at 560 Ω. The long-term operation under MFC mode demonstrated 0.27 V at 22 Ω and ~1kg/m3.d COD removal. Interrupted mode of operation provided more stable MFC output and prolonged cathode life span.

Figure 1
Impact of Oxygen on Glucose Oxidation Kinetics in a Redox Polymer Mediated Glucose Oxidase Electrode
Authors: Calabrese Barton Scott , Chakraborty Deboleena , Bambhania Harshal , Wen Hao
Published: February 2020

The kinetics of glucose oxidation by glucose oxidase (GOx) were evaluated with mediation by two different osmium redox polymers and in the presence and absence of oxygen (O2). A one- dimensional model was designed to incorporate the effect of O2 reduction, which competes with the mediator for electrons from glucose oxidation at GOx. Kinetic parameters were determined by fitting the experimental current density measurements for varying potential, glucose and O2 concentrations. It was demonstrated that the presence of O2 affects both the turnover number, kcat, and Michaelis constant, KM, of the enzyme, indicative of a mixed inhibition mechanism. Kinetic parameters specific to the mediator reaction were an order of magnitude higher than other homogeneous mediated systems, leading to high mediation efficiency. Bimolecular rate constants for GOx-oxygen reaction were found to be an order of magnitude lower than that of the free solution, which can be attributed to the reduced activity of immobilized GOx. 

Figure 1
Plasmonic Tungsten Oxide Nanowires for Visible-Light-Enhanced Hydrogen Generation
Authors: Xue Can
Published: February 2020

We present the preparation of plasmonic WO3-x nanowires via a surfactant-free solvothermal process which generates massive oxygen vacancies on WO3-x nanowires. As a result, the obtained WO3-x nanowires exhibit intensive LSPR absorption in the visible and NIR region. The surface plasmon excitation of WO3-x nanowires under visible/NIR light irradiation leads to significantly enhanced activity for hydrogen evolution from ammonia borane as compared to that in dark condition. The enhancement is attributed to the hot plasmon electrons that promote charge transfer between the reagents for hydrogen evolution on the WO3-x nanowire surface. In addition, the photothermal effect would supply additional localized heating on the WO3-x nanowire surface, and thereby increase reaction rate for more efficient H2 evolution. Furthermore, we also demonstrate that the plasmon excitation of Pd-loaded WO3-x nanowires by long wavelength irradiation can greatly promote chemical reactions catalyzed by the attached Pd nanoparticles.
(Keynote) Bioinspired Photoelectrode Assemblies for Solar Water or CO2 Splitting: At the Crossroads?
Authors: Rajeshwar Krishnan
Published: February 2020

The solar assisted splitting of water received great impetus as a legitimate research discipline as a result of the world energy crisis and the Arab oil embargo, and also from the initial reports of Fujishima, Honda, and their co-workers on the use of irradiated titanium dioxide. In the first part of the talk, the water splitting reaction and other reactions of technological interest will be discussed from the point of view of thermodynamics and kinetics. Approaches based on the use of electrodes and photoelectrodes as well as those based on the use of colloidal suspensions will be compared and contrasted.  Ideas on how we can learn from the intricate self-assembled architectures that Nature has evolved over millions of years, will be discussed with specific examples

The talk will then turn toward a discussion of the progress made with the generation of hydrogen as a renewable fuel and the notion of storing sunlight via chemical bonds (fuels). This will include work in the author’s laboratory on the use of carbon and oxide semiconductor nanocomposites for driving catalytic processes of interest both in the dark and under irradiation of the oxide semiconductor component. Incorporation of bioinspired components such as flavins in these assemblies will be described. The reactions of interest here include dioxygen reduction and the reduction of carbon dioxide to fuels such as methanol. The role of the nanocomposite components and their complementary functionality within the material architecture will be discussed within the context of systems that Nature has evolved. Other complex oxides and their preparation from solution combustion synthesis will also be elaborated.

Finally the talk will turn toward the very recent work in the author’s laboratory on the solar photoelectrosynthesis of methanol from CO2.  This process was driven on hybrid CuO/Cu2O semiconductor nanorod arrays for the first time at potentials ~800 mV below the thermodynamic threshold value and at Faradaic efficiencies of ~95%.  Subsequent studies have developed flow reactors as well as new electrode materials. 

The presently unknown aspects of this process as well as its "dark" process counterpart, especially details on how atomic hydrogen adds to the CO2 molecule along with scission of the carbon-oxygen double bond and even formation of carbon-carbon double bonds (in the formation of ethylene), will be discussed in the light of the
new
role that renewable hydrogen can play in the future.
(Invited) Stand-Alone Artificial Photosynthesis of Formate from CO2 and Water Using Copper and Iron Oxide Catalysts
Authors: Park Hyunwoong
Published: February 2020

Solar conversion of carbon dioxide and water to value-added chemicals remains a challenge. A number of solar-active catalysts have been reported but still suffer from low selectivity, poor energy efficiency, and instability, and fail to drive simultaneous water oxidation. Herein, we report CuFeO2 and CuO mixed p-type catalysts fabricated via a widely employed electroplating of earth-abundant cupric and ferric ions followed by annealing under atmospheric air. The composite electrodes exhibited onset potentials at +0.9 V vs. RHE in CO2-purged bicarbonate solution and converted CO2 to formate with over 90% selectivity under simulated solar light (Air Mass 1.5, 100 mW×cm-
2). Wired CuFeO2/CuO photocathode and Pt anode couples produced formate over 1 week at a solar-to-formate energy conversion efficiency of ~1% (selectivity >90%) without any external bias while O2 was evolved from water. Isotope and nuclear magnetic resonance analyses confirmed the simultaneous production of formate and O2 at the stand-alone couples.

Figure 1
(ECS Toyota Young Investigator Fellowship Program Address) Electrochemical Reduction of CO2(aq) By Solvated Electrons at a Plasma-Liquid Interface
Authors: Rumbach Paul , Xu Rui , Go David B.
Published: February 2020

While electron transfer reactions typically occur at the interface between a reactant and a metal in an electrolyte solution, it is also possible to initiate these reactions at the interface between a plasma (gas discharge) and a solution. In this case, a free, gaseous electron is injected into the solution from the plasma phase, solvating before reacting away. In our previous work, we have shown that an atmospheric pressure plasma in argon can be used as a cathode in an electrolytic cell to produce solvated electrons[1]. In this work, we show that the solvated electrons produced by the plasma cathode can be used to reduce dissolved carbon dioxide, CO2(aq), to form the carboxyl radical anion, CO2
–
(aq). The CO2
–
(aq) radical can either recombine to form oxalate under basic conditions or react with H+
(aq) to produce formate under acidic conditions.  We measure the Faradaic yield of both oxalate and formate formation using liquid ion chromatography and show that it is dictated by the well-known reaction kinetics of solvated electrons and CO2
–
(aq).  Importantly, these 3-dimensional reaction kinetics are distinct from the 2-dimensional kinetics found in traditional electrochemistry and catalysis, and may open up new opportunities to explore electrochemical carbon dioxide reforming.

[1]P. Rumbach, D.M. Bartels, R.M. Sankaran, and D.B. Go, Nature Comm.
6, 7248 (2015).
Electrocatalytic Mineralization of Urea in Aqueous Medium By Means of Ni(II)Cyclam-Modified Nanoparticulate TiO2 Anodes and Simultaneous Electrogeneration of H2 on Pt Cathodes
Authors: Murcio-Hernández Saacnhitee , Gonzalez Nava Catalina , Perez J. J. , Torres-González Julieta , Sepúlveda Selene , Godínez Mora-Tovar Luis Arturo , Rodriguez Valadez Francisco Javier , Rodríguez-García Adrián , Manríquez Juan
Published: February 2020

In this investigation we studied the electrocatalytic mineralization of urea contained in alkaline aqueous medium by means of Ni(II)cyclam-modified nanoparticulate TiO2 films (OTE/TiO2/Ni(II)cyclam, where an optically transparent electrode OTE was utilized as electrons collector) and the simultaneous electrogeneration of H2 through the H2O reduction on Pt cathodes which were inserted in the same cell. Our results showed that the standard potential for the H2 evolution (E°H2O/
H2 = -0.83V vs. NHE) was achieved on the Pt cathode when a potential of 1.0V vs. NHE was applied to the OTE/TiO2/Ni(II)cyclam//electrolyte interface (where the urea mineralization was taking place). On the contrary, the standard potential for the H2 evolution was achieved on the same Pt electrode when a potential of 1.2V vs. NHE was applied to the OTE/Ni(II)cyclam//electrolyte interface (in the absence of TiO2). These interesting results demonstrated that the urea oxidation potential on Ni(II)cyclam-modified OTEs was 0.2V cathodically-shifted in the presence of nanoparticulate TiO2.

Furthermore, H2 was continuously evolved for 1h from Pt cathodes in three-electrodes cells where aqueous urea solutions were simultaneously electrolyzed on OTE/TiO2/Ni(II)cyclam or OTE/Ni(II)cyclam electrodes. Interestingly, measurements of total organic carbon (TOC) which were carried out in the urea solutions with and without electrolytic treatment, revealed that the H2 evolution proceeds on a Pt cathode when the mineralization of urea achieves efficiencies of 20.8 and 10.4% on OTE/TiO2/Ni(II)cyclam and OTE/Ni(II)cyclam electrodes, respectively. These new results demonstrate that the OTE/TiO2/Ni(II)cyclam electrodes represents a novel pathway to carry out the electrochemical generation of H2 from urea as energy carrier.
Highly Sensitive and Selective Gas Sensors Based on Oxide Nanomaterials for Electronic Nose
Authors: Shim Young-Seok
Published: February 2020

The functional convergence of the Internet with radio-frequency identification and sensors has led to the era of the Internet of Things (IoT), which is a computing concept in which everyday objects are online and communicate via the Internet. In particular, the IoT is effective and appropriate for monitoring and controlling objects in hazardous environments to enable people to access them. In order to apply gas sensors to the IoT, operation at room temperature (low power consumption), a high efficiency (sensitivity, response/recovery time, and stability), low-cost fabrication, miniaturization, and easy integration with circuits are essential because these factors enhance the feasibility of utilizing a gas sensor, thereby enabling the collection, processing, analysis, and dissemination of valuable information gathered from a variety of environments. Among various types of gas sensors, semiconducting gas sensors based on various metal oxides are considered to be the strongest candidate for the application in IoT owing to their small size, simplicity in operation, low cost, and compatibility with integrated circuits. A wide variety of nanostructured metal oxides, including nanowire, nanobelt, nanorods, nanosheets, nanospheres, and nanotubes has been exploited for semiconductor gas sensors during the past decade. Despite these efforts, achieving a reproducible fabrication, easy integration with other circuits, and compatibility with well-established semiconductor production processes that are related to mass production have remained challenges for the utilization of the semiconducting sensors in the IoT.

 In the presentation, we show our research efforts to synthesize well-ordered metal-oxide nanostructures such as nanorods, nanohemispheres, nanospheres and nanowells using physical vapor deposition (PVD) methods for the high performance chemoresistive gas sensors.
(Invited) Chip Based Electrochemical Imaging of Neuron Transmitters Expression at Single PC12 Cell and 3-D Spheroids Level
Authors: Li Chen Zhong , Shah Pratikkumar , Ino Kosuke , Matsue Tomokazu , Yue Qiaoli , Chen Chunying
Published: February 2020

Understanding and controlling the interface between neuronal cells and neuronal network and electrical devices is vital to both biological science and technology.    Recent developments in the field of in vitro neuron mapping focus on the development of optical and electrochemical strategies for either single neuron cell/neuron measurement or artificial neuronal networks/brain slices mapping. To mimic in vivo neuronal networks and to elucidate the mechanisms of computation, spontaneous and elicited electrical activity need to be monitored, and multiple simultaneous recordings are required for monitoring individual unit and collective network activity. In this way, both individual cells and cell networks can be scrutinized in order to understand how changes in single unit activity and functionality. In the present study, we developed a large-scale integration -based amperometric sensor array system for electrochemical bioimaging and throughput sensing of dopamine expression from three-dimensional (3D)-cultured PC12 cells upon dopaminergic drugs exposure. It has been shown that individual cells behave differently from the population even under the identical conditions, as a complementary study, we also explore the possibility of single cell-on-chip based analytical technique which can collect real-time change in cell physiology by measurement of cell exocytosis, i.e., release of neurotransmitters, in a neuronal model cell line, i.e. PC12 cells. The study of single cell dynamics could help us better understand the complex processes, such as, neurotransmitter kinetics, ion channel functions, and cell communications, single cell analysis can be an equivalent and complementary strategy to existing approaches.
Electrochemical Detection of Bacteria Using Portable Paper-Based Culture Devices
Authors: Deiss Frédérique , Metangmo Armelle
Published: February 2020

Testing of food and water samples for viruses and bacteria in a rapid, portable, quantitative way is of growing interest as much for government, farmers, industrials, as end-consumers. In the past two decades, many research groups were involved in the development of various paper-based devices for quantitative or semi-quantitative detection of clinically relevant analytes and in particular pathogens.

Some difficulties remain in analyzing samples with complex matrices (e.g., colored samples or muddy water), with enough sensitivity (e.g., detecting less than 10-100 cfu/mL) while minimizing culture time. Electrochemical detection can allow for rapid quantification over a wide dynamic range, with a low limit of detection, and without limitations related to presence of colors or particles in samples. Derda and co-workers validated growth of bacteria in portable paper-based culture devices [1, 2]. We added screen-printed electrodes onto those paper-based devices (Figure A-B) to allow for electrochemical detection of micro-organisms. The presence of bacteria in the device, and particularly on the electrode, bacteria affects the characteristics of the electrode. By measuring those changes by electrochemical impedance spectroscopy, for example, we could detect the bacteria (Figure E).

The platform can be selective to bacteria by immobilizing on the electrode proximity antibodies specific to the bacteria to detect, and thus enhancing the presence of the bacteria on the electrode.

Using the paper-based portable culture device instead of metal electrodes as reported previously [3] as a support as multiple advantages: in addition to allow for an easy- sampling at the point-of-care or in-field, if the sample has a low number of bacteria (Figure C), it can be cultured in the same device and tested again once more bacteria is present (Figure D) without additional handling of the sample. The use of paper in these devices made them user-friendly, portable, light-weight, low-cost, easy to manufactured and disposed of once contaminated (e.g., burning).

References

1.    Deiss, F.; Funes-Huacca, M. E.; Bal, J.; Tjhung, K. F.; Derda, R., Antimicrobial susceptibility assays in paper-based portable culture devices. Lab on a Chip
2014,14, (1), 167.

2.    Funes-Huacca, M.; Wu, A.; Szepesvari, E.; Rajendran, P.; Kwan-Wong, N.; Razgulin, A.; Shen, Y.; Kagira, J.; Campbell, R.; Derda, R., Portable self-contained cultures for phage and bacteria made of paper and tape. Lab on a Chip
2012,12, (21), 4269.

3.    Lu, L.; Chee, G.; Yamada, K.; Jun, S., Electrochemical impedance spectroscopic technique with a functionalized microwire sensor for rapid detection of foodbornepathogens. Biosensors and Bioelectronics
2013, 42, (0), 492.

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-2 at a 30 mM glucose concentration.

Key words: Glucose dehydrogenase, FAD, Os-polymers, glucose biosensor, chronoamperometry, oxygen reactivity.
Comparative Electroanalytical Study on Fabrication of CN Selective Sensor Based on Polymeric Membrane Electrode and Coated Graphite Electrode
Authors: Singh Ashok KUMAR , Bhardwaj Shubhrajyotsna
Published: February 2020

The construction and general performance characteristics of PVC-based cyanide selective polymeric membrane electrode (PME) and coated graphite electrode (CGE) incorporating the synthesized 2,4-di-tert-butyl-6-((2(2,4-dinitrophenyl)hydrazono)methyl)phenol (I) is described here. Effect of various plasticizers (o-nitrophenyloctyl ether, oleic acid, dibutylsebacate, dibutylphthalate, tri-n-butylphosphate) and  cation  excluder,  Cetryltrimethylammoniumbromide (CTAB) was studied by constructing membranes having different compositions. The best performance was observed for the membrane having composition of  I: PVC: oNPOE: CTAB ratio of 3.5: 36: 58: 2.5 (w/w; mg). So the coated graphite electrode (CGE) using same composition was also constructed and the sensor displays significantly improved selectivity  towards CN‾ion. The response features of PME based on the above stated membrane composition was also compared with CGE. The electrode exhibits Nernstian slope for CN‾ions over wide concentration ranges i.e. 8.3 × 10-6 to 1.0 × 10-1 mol L-1 (with PME) and 5.87×10-7 – 1.0×10-1 mol L-1 (with CGE) and response time of 13 s and 10 s for PME and CGE respectively. CGE exhibits low detection limit 3.6×10-8 mol L-1 with Nernstian slope -58.8 ± 0.2 mV decade-1. Furthermore, the electrode shows constant potentials in the pH range of 6-8 and can be used for about 3 months without any significant deviation in their potential response. The selectivity of the sensor is fairly good over most common anions. The extraordinary selectivity of CGE for CN‾ion permits its practice in the determination of CN‾ion in water and edible samples. Practice of the sensor for potentiometric detection of microgram measures of CN‾ion displays an average regaining of 99.5% and a mean standard deviation of 0.5% and the results attained are comparable with those delivered by AAS analysis.
Integrated-Evanescent Raman Sensors Based on Titanium-Dioxide Nanophotonics
Authors: Evans Christopher C. , Liu Chengyu , Suntivich Jin
Published: February 2020

The success of next-generation chemical monitoring and molecular identification technologies hinges on the ability to resolve between different chemical environments. Fully-integrated evanescent Raman spectrometers can provide this solution; however, current materials used in excitation and collection optics are limited to near-infrared wavelengths, which have reduced Raman cross-sections when compared to visible wavelengths, and are not compatible with visible lasers and detectors. Here, we show that titanium dioxide (TiO2) can serve a new material platform for evanescent Raman spectroscopy that can address these challenges. We experimentally show that visible TiO2 nanophotonics increases the internal efficiency of the Raman scattering by more than two orders of magnitude over previous reports. Our TiO2 nanophotonics demonstrate a material solution to the chemical sensing challenge and an opportunity to enhance future sensing functionalities of nanophotonics by innovating at the material level.
Theory of the Manganese Disproportionation at the (100) Surface of LiMn2O4
Authors: Liu Cong , Voeroes Marton , Iddir Hakim , Benedek Roy , Curtiss Larry
Published: February 2020

Owing to its ease of preparation, low cost and non-toxicity, LiMn2O4 (LMO) has become a promising candidate to replace LiCoO2 as a cathode material in high power Li-ion batteries. However, the performance of LiMn2O4 cathode is limited by capacity fade, particularly at high temperatures. It is believed that the capacity fade of LiMn2O4 is driven by the loss of Mn resulting from the disproportionation of surface Mn3+ with the resultant divalent Mn ions dissolving into stray moisture and electrolyte. In this work, we explore the mechanism of Mn disproportionation at the surface of LiMn2O4 using theoretical approaches, based on density functional theory to determine the mechanism of disproportionation and the effect of surface dopants. The thermodynamic driving force for disproportionation for different surface compositions will be discussed.
The Decomposition Mechanism of Crystalline Lioh on Ruthenium in Non-Aqueous Lithium-Oxygen Batteries: A First-Principles Study
Authors: Jiang Haoran , Zhao Tianshou
Published: February 2020

Non-aqueous lithium-oxygen (Li-O2) batteries are considered as the potential energy storage system for electric vehicles due to its comparable energy density (11682 W h kg-1) with gasoline (13000 W h kg-1) [1]. However, the development of Li-O2 batteries is still at its early stage and suffers from some critical issues, such as short cycle life, poor electrolyte and electrode stabilities, and low energy efficiency [2], most of which are related to the high charge overpotential during the oxygen evolution reaction (OER). One widely applied approach to decrease the high charge overpotential is using catalyst, such as carbon-based materials, noble metals, metal oxides and so on. Even with this effort, however, it is still difficult to lower the charge voltage as much as possible (e.g. 3.5 V) to ensure the stabilities of electrolyte and electrode materials when Li2O2 is the discharge product [3]. Recently, an alternative strategy that achieves an ultra-low charge ovepotential and excellent stability has been reported, which is to form solid-state LiOH rather than Li2O2in the discharge process [4, 5]. However, the mechanism of crystalline LiOH decomposition on catalysts is still unknown, and the possible catalysts that can promote the decomposition of solid-state LiOH are also limited.

In this regard, a first-principles study was used to investigate the OER process in non-aqueous Li-O2batteries via LiOH formation and decomposition. We developed an interfacial model to study the decomposition mechanism of LiOH on different surfaces of ruthenium, and the charge overpotentials among different surfaces were compared. Moreover, the decomposition path of crystalline LiOH and the rate determining step (RDS) were investigated. Our results demonstrate the activity of ruthenium towards the decomposition of crystalline LiOH, and different surfaces can lead to the different decomposition paths.

Further analysis of the decomposition mechanism of crystalline LiOH will be presented at the meeting. Our investigations give new insight into the future catalyst design in non-aqueous Li-O2batteries.

References                                                         

[1] G. Girishkumar, B. McCloskey, A. Luntz, S. Swanson and W. Wilcke, The Journal of Physical Chemistry Letters, vol. 1, pp. 2193-2203, 2010.

[2] J. Christensen, P. Albertus, R. S. Sanchez-Carrera, T. Lohmann, B. Kozinsky, R. Liedtke, J. Ahmed and A. Kojic, J. Electrochem. Soc., vol. 159, pp. R1-R30, 2011.                                

[3] M. M. Ottakam Thotiyl, S. A. Freunberger, Z. Peng and P. G. Bruce, J. Am. Chem. Soc., vol. 135, pp. 494-500, 2012.                                                              

[4] F. Li, S. Wu, T. Zhang, P. He, A. Yamada and H. Zhou, Nature Communications, vol. 6, 2015.                                                         

[5] T. Liu, M. Leskes, W. Yu, A. J. Moore, L. Zhou, P. M. Bayley, G. Kim and C. P. Grey, Science, vol. 350, pp. 530-533, Oct 30, 2015.