The Experts below are selected from a list of 279 Experts worldwide ranked by ideXlab platform
Frank Marken - One of the best experts on this subject based on the ideXlab platform.
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Generator–Collector electrochemical sensor configurations based on track-Etch membrane separated platinum leaves
Sensors and Actuators B: Chemical, 2018Co-Authors: Hamid Reza Zafarani, Liza Rassaei, Ernst J. R. Sudhölter, Barak D. B. Aaronson, Frank MarkenAbstract:Abstract We report a novel, simple and cheap generator–Collector Electrode system, employing platinum leaves, with micron-sized pores and typically 100–300 nm thickness, sandwiched with a porous track etch membrane spacer with typically 30 nm diameter pores. The Electrode assembly is sealed into a polymer lamination pouch with one side 2 mm diameter exposed to electrolyte solution. The generator Electrode with sweeping potential (top or bottom Electrode) shows transient current with high capacitive current component. The Collector Electrode with fixed potential shows well-defined steady state current response at low potential sweep rates. The fabricated device shows good performance in monitoring both 1,1′-ferrocenedimethanol oxidation and proton reduction redox processes. Oxygen sensor signals are assigned to a lowering of the steady state proton reduction current.
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Dual-Plate Gold-Gold Microtrench Electrodes for Generator-Collector Voltammetry without Supporting Electrolyte
Electrochimica Acta, 2017Co-Authors: Miguel A. Montiel, Jesús Iniesta, Andrew J. Gross, Frank MarkenAbstract:Abstract A gold-gold dual-plate microtrench Electrode system based on two oppositely placed gold surfaces with 5 mm length, 17 μm average depth, and 6 μm inter-Electrode gap is employed in generator-Collector configuration in a four-Electrode cell (counter Electrode, reference Electrode, and two independent working Electrodes denoted “generator” – with scanning potential – and “Collector” – with fixed potential). The dual-plate microtrench Electrodes were investigated for (i) the reduction of Ru(NH3)63+, (ii) the oxidation of ferrocenemethanol, and (iii) the oxidation of iodide in aqueous media, all as a function of supporting electrolyte concentration. It is shown that due to the inter-Electrode feedback character of the generator-Collector currents, well-defined steady state sensor responses are obtained for the Collector Electrode even in the absence of added electrolyte. The variation in the mass transport limited steady state current (measured at the Collector Electrode) with addition/removal of supporting electrolyte remains low (compared to unexpectedly stronger effects caused by the switch between reduction and oxidation conditions at the Collector Electrode). Microtrench Electrode systems are suggested for sensing applications without/with varying levels of supporting electrolyte.
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nano litre proton hydrogen titration in a dual plate platinum platinum generator Collector Electrode micro trench
Electrochimica Acta, 2014Co-Authors: Sara E C Dale, Anne Vuorema, Mika Sillanpaa, James Weber, Andrew J Wain, Edward O Barnes, Richard G Compton, Frank MarkenAbstract:Abstract A generator-Collector “nano-litre cavity” based on two opposed platinum-coated gold film Electrodes with 19 μm gap and either 38 μm or 83 μm depth is employed for the titration of protons and/or hydrogen. Diffusional feedback currents between generator and Collector Electrode in a platinum-platinum dual-plate sensor configuration provide a sensitive analytical tool for cycleable redox systems, here, the proton/hydrogen redox system in the presence of oxygen. Experimental data are compared with the theoretical expression proposed by Hubbard and Peters (A.T. Hubbard, D.G. Peters, Critical Reviews in Analytical Chemistry, 1973, 3, 201-242) suggesting a dominating transport effect of “slow diffusers”. Good agreement is observed even at relatively high proton concentrations where hydrogen bubble nucleation within the micro-trench starts to occur. Low concentration measurements are strongly affected by oxygen reduction locally consuming/depleting protons. Catalytic activity of the platinum deposit is crucial for maximising the current output.
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a dual plate ito ito generator Collector microtrench sensor surface activation spatial separation and suppression of irreversible oxygen and ascorbate interference
Analyst, 2014Co-Authors: M A Hasnat, Sara E C Dale, Edward O Barnes, Richard G Compton, Andrew J. Gross, Frank MarkenAbstract:Generator–Collector Electrode systems are based on two independent working Electrodes with overlapping diffusion fields where chemically reversible redox processes (oxidation and reduction) are coupled to give amplified current signals. A generator–Collector trench Electrode system prepared from two tin-doped indium oxide (ITO) Electrodes placed vis-a-vis with a 22 μm inter-Electrode gap is employed here as a sensor in aqueous media. The reversible 2-electron anthraquinone-2-sulfonate redox system is demonstrated to give well-defined Collector responses even in the presence of oxygen due to the irreversible nature of the oxygen reduction. For the oxidation of dopamine on ITO, novel “Piranha-activation” effects are observed and chemically reversible generator–Collector feedback conditions are achieved at pH 7, by selecting a more negative Collector potential, again eliminating possible oxygen interference. Finally, dopamine oxidation in the presence of ascorbate is demonstrated with the irreversible oxidation of ascorbate at the “mouth” of the trench Electrode and chemically reversible oxidation of dopamine in the trench “interior”. This spatial separation of chemically reversible and irreversible processes within and outside the trench is discussed as a potential in situ microscale sensing and separation tool.
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Nano-litre proton/hydrogen titration in a dual-plate platinum-platinum generator-Collector Electrode micro-trench
Electrochimica Acta, 2014Co-Authors: Sara E C Dale, Anne Vuorema, Mika Sillanpaa, James Weber, Andrew J Wain, Edward O Barnes, Richard G Compton, Frank MarkenAbstract:Abstract A generator-Collector “nano-litre cavity” based on two opposed platinum-coated gold film Electrodes with 19 μm gap and either 38 μm or 83 μm depth is employed for the titration of protons and/or hydrogen. Diffusional feedback currents between generator and Collector Electrode in a platinum-platinum dual-plate sensor configuration provide a sensitive analytical tool for cycleable redox systems, here, the proton/hydrogen redox system in the presence of oxygen. Experimental data are compared with the theoretical expression proposed by Hubbard and Peters (A.T. Hubbard, D.G. Peters, Critical Reviews in Analytical Chemistry, 1973, 3, 201-242) suggesting a dominating transport effect of “slow diffusers”. Good agreement is observed even at relatively high proton concentrations where hydrogen bubble nucleation within the micro-trench starts to occur. Low concentration measurements are strongly affected by oxygen reduction locally consuming/depleting protons. Catalytic activity of the platinum deposit is crucial for maximising the current output.
Jesus Grajal - One of the best experts on this subject based on the ideXlab platform.
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Remote collection and measurement of photogenerated carriers swept by surface acoustic waves in GaN
Applied Physics Letters, 2004Co-Authors: Tomas Palacios, Fernando Calle, Jesus GrajalAbstract:The interaction of surface acoustic waves and photogenerated carriers in GaN has been used for the fabrication of a remote ultraviolet detector where the carrier Collector Electrode is far away from the illuminated region. In this device, the recombination of the photogenerated carriers at the region where they are created is prevented by the potential fields associated with the acoustic wave, and the carriers are swept by the acoustic wave to the Collector Electrode. This effect is strongly dependent on the frequency and power of the acoustic waves and therefore of the input radio frequency signal. New optoelectronic devices based on the combination of the acoustic and electronic properties of the semiconductors can be envisaged.
Tooru Tsuru - One of the best experts on this subject based on the ideXlab platform.
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channel flow double Electrode study on palladium dissolution during potential cycling in sulfuric acid solution
Electrochimica Acta, 2012Co-Authors: Buddha Ratna Shrestha, Atsushi Nishikata, Tooru TsuruAbstract:Abstract Channel flow double Electrode (CFDE) was applied to study palladium dissolution during potential cycling in 0.5 M H 2 SO 4 solution at 25 °C. In the CFDE, Pd ions (Pd n + ) dissolved from a Pd working Electrode were detected by reducing them to Pd on a gold Collector Electrode, which was placed at the downstream. The detection of the Pd dissolution by the Collector current was confirmed by (Electron Probe Micro Analyzer) EPMA analysis of the Collector Electrode surface. In anodic scan, gradual rise of the Collector current till 0.7 V indicated Pd dissolution. The dissolution was confirmed by EPMA. Anodic as well as cathodic dissolution was confirmed when potential cycling was done till 0.8 V. Dissolution of palladium was found to increase anodically as well as cathodically when upper limit of polarization was increased. From Collector current and the results of EPMA, the dissolution mechanism is proposed.
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application of channel flow double Electrode to the study on gold dissolution during potential cycling in sulfuric acid solution
Journal of Electroanalytical Chemistry, 2012Co-Authors: Buddha Ratna Shrestha, Atsushi Nishikata, Tooru TsuruAbstract:Abstract The applicability of a channel flow double Electrode (CFDE) as an in situ monitoring method of gold dissolution during potential cycling in 0.5 M H 2 SO 4 solution at 25 °C was investigated. In the CFDE, Au ions (Au n + ) dissolved from a gold working Electrode were detected by reducing them to Au on Collector Electrode (Au/Pt) which was placed at the downstream. The detection of the Au dissolution was confirmed by EPMA analysis of the Collector Electrode (Pt) surface. In anodic scan, a rise of the Collector current above 1.35 V clearly indicated gold dissolution. Initially, the dissolution increased with increased anodic potential, but later limiting dissolution was observed above 1.55 V. The Collector current, in the cathodic scan, clearly showed a reduction peak which was confirmed by EPMA analysis to be due to the gold deposition. On the basis of Collector current, the rate and potential range of the Au dissolution are discussed. The amount of gold dissolved was found to be 4.2 μC cm −2 cycle −1 when potential cycling from 0.4 to 1.6 V in 0.5 M H 2 SO 4 . Thus, upon meticulous and exhaustive deaeration, channel flow double Electrode was found to be a highly sensitive method applicable to monitor the dissolution behavior of even the noblest element gold.
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application of channel flow double Electrode to the study on platinum dissolution during potential cycling in sulfuric acid solution
Electrochimica Acta, 2011Co-Authors: Buddha Ratna Shrestha, Atsushi Nishikata, Amar Prasad Yadav, Tooru TsuruAbstract:Abstract The applicability of a channel flow double Electrode (CFDE) as an in situ monitoring method of Pt dissolution during potential cycling in 0.5 M H2SO4 solution at 25 °C was investigated. In the CFDE, Pt ions (Ptn+) dissolved from a platinum working Electrode were detected by reducing them to Pt on a gold Collector Electrode which was placed at the downstream. The detection of the Pt dissolution by the Collector current was confirmed by EPMA analysis of the Collector Electrode surface. In anodic scan, a rise of the Collector current above 1.05 V clearly indicated the platinum dissolution. The Collector current showed two different rates of dissolution, i.e. a lower rate from 1.05 to 1.3 V where only one layer of oxide (PtO) is formed and the higher rate from 1.3 to 1.46 V where two layers of oxides (probably PtO/PtO2) are formed. The Collector current, in the cathodic scan, clearly showed two different reduction peaks due to the Pt deposition, which was confirmed by EPMA analysis. On the basis of Collector current, the rate and potential range of the Pt dissolution are discussed.
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channel flow double Electrode study on the dissolution and deposition potentials of platinum under potential cycles
Journal of The Electrochemical Society, 2009Co-Authors: Amar Prasad Yadav, Atsushi Nishikata, Tooru TsuruAbstract:A channel-flow double-Electrode system has been employed to determine the potential regions of Pt dissolution and redeposition during a cyclic voltammetry (CV) measurement in 0.5 M H 2 SO 4 solution at 25°C. The double-Electrode system consists of a Pt plate as a working Electrode (WE) placed upstream and a Au plate as a Collector Electrode (CE) placed downstream with a separation gap of 0.1 mm. Pt ions dissolved at the WE during CV have been detected at the CE by employing an appropriate reduction potential and have been analyzed by using an electron probe microanalyzer (EPMA). The EPMA results show that the deposition of Pt from hydrated Pt ions occurs below 0.60 V vs the standard hydrogen Electrode. When CV is carried out between 0.0 and 1.4 or 1.6 V, dissolution of Pt occurs during both the anodic and cathodic scans of the CV. When CV is carried out between 0.0 V and an upper potential limit of 1.2 V, the dissolution of Pt could be observed only in the anodic scan. The dissolution mechanism of Pt during CV is proposed.
Richard G Compton - One of the best experts on this subject based on the ideXlab platform.
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nano litre proton hydrogen titration in a dual plate platinum platinum generator Collector Electrode micro trench
Electrochimica Acta, 2014Co-Authors: Sara E C Dale, Anne Vuorema, Mika Sillanpaa, James Weber, Andrew J Wain, Edward O Barnes, Richard G Compton, Frank MarkenAbstract:Abstract A generator-Collector “nano-litre cavity” based on two opposed platinum-coated gold film Electrodes with 19 μm gap and either 38 μm or 83 μm depth is employed for the titration of protons and/or hydrogen. Diffusional feedback currents between generator and Collector Electrode in a platinum-platinum dual-plate sensor configuration provide a sensitive analytical tool for cycleable redox systems, here, the proton/hydrogen redox system in the presence of oxygen. Experimental data are compared with the theoretical expression proposed by Hubbard and Peters (A.T. Hubbard, D.G. Peters, Critical Reviews in Analytical Chemistry, 1973, 3, 201-242) suggesting a dominating transport effect of “slow diffusers”. Good agreement is observed even at relatively high proton concentrations where hydrogen bubble nucleation within the micro-trench starts to occur. Low concentration measurements are strongly affected by oxygen reduction locally consuming/depleting protons. Catalytic activity of the platinum deposit is crucial for maximising the current output.
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a dual plate ito ito generator Collector microtrench sensor surface activation spatial separation and suppression of irreversible oxygen and ascorbate interference
Analyst, 2014Co-Authors: M A Hasnat, Sara E C Dale, Edward O Barnes, Richard G Compton, Andrew J. Gross, Frank MarkenAbstract:Generator–Collector Electrode systems are based on two independent working Electrodes with overlapping diffusion fields where chemically reversible redox processes (oxidation and reduction) are coupled to give amplified current signals. A generator–Collector trench Electrode system prepared from two tin-doped indium oxide (ITO) Electrodes placed vis-a-vis with a 22 μm inter-Electrode gap is employed here as a sensor in aqueous media. The reversible 2-electron anthraquinone-2-sulfonate redox system is demonstrated to give well-defined Collector responses even in the presence of oxygen due to the irreversible nature of the oxygen reduction. For the oxidation of dopamine on ITO, novel “Piranha-activation” effects are observed and chemically reversible generator–Collector feedback conditions are achieved at pH 7, by selecting a more negative Collector potential, again eliminating possible oxygen interference. Finally, dopamine oxidation in the presence of ascorbate is demonstrated with the irreversible oxidation of ascorbate at the “mouth” of the trench Electrode and chemically reversible oxidation of dopamine in the trench “interior”. This spatial separation of chemically reversible and irreversible processes within and outside the trench is discussed as a potential in situ microscale sensing and separation tool.
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Nano-litre proton/hydrogen titration in a dual-plate platinum-platinum generator-Collector Electrode micro-trench
Electrochimica Acta, 2014Co-Authors: Sara E C Dale, Anne Vuorema, Mika Sillanpaa, James Weber, Andrew J Wain, Edward O Barnes, Richard G Compton, Frank MarkenAbstract:Abstract A generator-Collector “nano-litre cavity” based on two opposed platinum-coated gold film Electrodes with 19 μm gap and either 38 μm or 83 μm depth is employed for the titration of protons and/or hydrogen. Diffusional feedback currents between generator and Collector Electrode in a platinum-platinum dual-plate sensor configuration provide a sensitive analytical tool for cycleable redox systems, here, the proton/hydrogen redox system in the presence of oxygen. Experimental data are compared with the theoretical expression proposed by Hubbard and Peters (A.T. Hubbard, D.G. Peters, Critical Reviews in Analytical Chemistry, 1973, 3, 201-242) suggesting a dominating transport effect of “slow diffusers”. Good agreement is observed even at relatively high proton concentrations where hydrogen bubble nucleation within the micro-trench starts to occur. Low concentration measurements are strongly affected by oxygen reduction locally consuming/depleting protons. Catalytic activity of the platinum deposit is crucial for maximising the current output.
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Generator/Collector Experiments with a Single Electrode: Introduction and Application to Exploring the Oxidation Mechanism of Serotonin
The Journal of Physical Chemistry C, 2009Co-Authors: Martin C. Henstridge, Gregory G. Wildgoose, Richard G ComptonAbstract:The facile chemical modification of a graphite Electrode with pH sensitive redox active molecules results in the formation of a generator/Collector Electrode system using a single Electrode. Using the oxidation of serotonin as a model system, we demonstrate that the single generator/Collector Electrode is capable of measuring changes in local pH immediately adjacent to the Electrode surface, i.e., within the diffusion layer during the oxidation process. Comparison of experimental data with numerical simulations was used to ascertain that the serotonin oxidation mechanism in poorly buffered media initially involves the transfer of two electrons and only one proton in an electrochemical, chemical, electrochemical (ECE) mechanism. This approach compares favorably in terms of sensitivity to traditional double-Electrode experiments such as the use of rotating ring-disk Electrodes.
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Microwave-enhanced electroanalytical processes: generator–Collector voltammetry at paired gold Electrode junctions
The Analyst, 2009Co-Authors: Liza Rassaei, Richard G Compton, Robert W. French, Frank MarkenAbstract:Generator–Collector Electrode systems allow redox processes and reaction intermediates from multi-step Electrode reactions to be monitored. Analytically, Collector Electrode current responses are insightful and highly sensitive due to (i) the absence of capacitive current components and (ii) an enhanced current response due to ‘feedback’ between generator and Collector Electrode. Here, a symmetric gold–gold junction grown by controlled electro-deposition is employed for generator–Collector voltammetry in conjunction with microwave activation. Three redox systems are investigated in aqueous 0.1 M KOH: (i) the reduction of Fe(CN)63−, (ii) the reduction of chloramphenicol, and (iii) the reduction of oxygen. Microwave radiation, when focused into the Electrode–solution interfacial zone, causes locally enhanced temperatures with Electrode surface temperatures reaching up to typically 380 K (estimated from the shift in the Fe(CN)63−/4− equilibrium potential, at both gold Electrodes). The resulting increase in the rate of diffusion and the onset of convection result in non-linear Arrhenius limiting current characteristics and in an increase in collection efficiency with microwave power. The gold Electrode junction geometry allows diffusion effects (which increase the feedback current within the gap) to dominate over convection effects (which suppress the feedback current).
Tomas Palacios - One of the best experts on this subject based on the ideXlab platform.
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Remote collection and measurement of photogenerated carriers swept by surface acoustic waves in GaN
Applied Physics Letters, 2004Co-Authors: Tomas Palacios, Fernando Calle, Jesus GrajalAbstract:The interaction of surface acoustic waves and photogenerated carriers in GaN has been used for the fabrication of a remote ultraviolet detector where the carrier Collector Electrode is far away from the illuminated region. In this device, the recombination of the photogenerated carriers at the region where they are created is prevented by the potential fields associated with the acoustic wave, and the carriers are swept by the acoustic wave to the Collector Electrode. This effect is strongly dependent on the frequency and power of the acoustic waves and therefore of the input radio frequency signal. New optoelectronic devices based on the combination of the acoustic and electronic properties of the semiconductors can be envisaged.