bluuebunny/crossref_metadata_2025_split 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.
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) 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
(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.