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Thomas S Varley - One of the best experts on this subject based on the ideXlab platform.
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in situ spectroelectrochemistry and colour measurement of a complementary electrochromic device based on surface confined prussian blue and aqueous solution phase Methyl Viologen
Solar Energy Materials and Solar Cells, 2012Co-Authors: Roger J Mortimer, Thomas S VarleyAbstract:Abstract The fabrication, in situ spectroelectrochemistry and colour measurement of hybrid electrochromic devices (ECDs) based on a surface-confined metal hexacyanometallate – Prussian blue (PB, containing the iron(III) hexacyanoferrate(II) chromophore) – and aqueous solution-phase Methyl Viologen ( N , N ′-diMethyl-4,4′-bipyridylium) are described. In the ECDs, the initial (‘off’) bleached state is set with PB in its reduced form and the Methyl Viologen as the di-cation. Switching to the coloured state (‘on’), forms the mixed-valence iron(III) hexacyanoferrate(II) chromophore upon oxidation of iron(II) hexacyanoferrate(II), with simultaneous reduction of the Methyl Viologen di-cation to form a mixture of the radical cation monomer/dimer. Using the Commission Internationale de l'Eclairage (CIE) system of colorimetry, the colour stimulus of such ECDs and the changes that take place on reversibly switching between the colourless and coloured states have been calculated from in situ visible region spectra recorded under electrochemical control. The concentration of the solution-phase Methyl Viologen and its diffusion to the cathode controlled both the proportion of surface-confined (reduced) PB that is switched to the blue form and the overall ECD changes. For the ECDs' ‘on’ states, the CIELAB 1976 colour space coordinates for a D55 illuminant were L ⁎ =60, a ⁎ =3 and b ⁎ =−46, and L ⁎ =49, a ⁎ =9 and b ⁎ =−59, respectively for 5 and 10 mM Methyl Viologen solution concentrations. The low a ⁎ and high (negative) b ⁎ chromaticity coordinates quantified the overall ECD colour stimulus of the ‘on’ state as being deep blue, with a broad absorption across the visible spectral region. CIELAB 1976 colour space coordinates showed that the ECDs were fully transparent and nearly colourless in the ‘off’ states, with L ⁎ =100, a ⁎ =1 and b ⁎ =1. The changes in the transparency were 83.0% (5 mM Methyl Viologen) and 93.1% (10 mM Methyl Viologen) between the ‘off’ (bleached) and ‘on’ (coloured) states of the ECDs.
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novel color reinforcing electrochromic device based on surface confined ruthenium purple and solution phase Methyl Viologen
Chemistry of Materials, 2011Co-Authors: Roger J Mortimer, Thomas S VarleyAbstract:A novel color-reinforcing electrochromic device (ECD) is described in which the anode and cathode reactions simultaneously exhibit reversible colorless to intense purple changes. Under coloration, the mixed-valence iron(III) hexacyanoruthenate(II) chromophore is formed on oxidation of iron(II) hexacyanoruthenate(II), with simultaneous reduction of the Methyl Viologen dication to form a mixture of the radical cation monomer/dimer. Using the CIE (Commission Internationale de l’Eclairage) system of colorimetry, the color stimulus of such ECDs and the changes that take place on reversibly switching between the colored and colorless states have been calculated from in situ visible spectra recorded under electrochemical control. On ECD color switching, with the excellent color-matching between the two purple states, sharp and reversible changes in the hue and saturation occur, as shown by the minimal hysteresis of the track of the CIE 1931 xy chromaticity coordinates. Extrapolation of the xy track to the color ...
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novel color reinforcing electrochromic device based on surface confined ruthenium purple and solution phase Methyl Viologen
Chemistry of Materials, 2011Co-Authors: Roger J Mortimer, Thomas S VarleyAbstract:A novel color-reinforcing electrochromic device (ECD) is described in which the anode and cathode reactions simultaneously exhibit reversible colorless to intense purple changes. Under coloration, the mixed-valence iron(III) hexacyanoruthenate(II) chromophore is formed on oxidation of iron(II) hexacyanoruthenate(II), with simultaneous reduction of the Methyl Viologen dication to form a mixture of the radical cation monomer/dimer. Using the CIE (Commission Internationale de l’Eclairage) system of colorimetry, the color stimulus of such ECDs and the changes that take place on reversibly switching between the colored and colorless states have been calculated from in situ visible spectra recorded under electrochemical control. On ECD color switching, with the excellent color-matching between the two purple states, sharp and reversible changes in the hue and saturation occur, as shown by the minimal hysteresis of the track of the CIE 1931 xy chromaticity coordinates. Extrapolation of the xy track to the color ...
Richard G Compton - One of the best experts on this subject based on the ideXlab platform.
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single entity electrocatalysis oxygen reduction mediated via Methyl Viologen doped nafion nanoparticles
Physical Chemistry Chemical Physics, 2018Co-Authors: Lifu Chen, Chuhong Lin, Richard G ComptonAbstract:Nafion particles doped with Methyl Viologen are shown to be electrocatalytic towards oxygen reduction in aqueous solution when immobilised on a carbon electrode surface, with the formation of hydrogen peroxide. In this way an efficient homogeneous electron transfer mediator, Methyl Viologen, can be confined to act heterogeneously with the benefits of that type of process without losing effectiveness. Kinetic and mechanistic parameters are deduced from cyclic voltammetry and from single entity nano-impact experiments, and the process is shown to occur via electron transfer to dioxygen at the Nafion particle–solution interface with the initial formation of superoxide.
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Nafion particles doped with Methyl Viologen: electrochemistry
Physical chemistry chemical physics : PCCP, 2017Co-Authors: Haiying Yang, Christopher Batchelor-mcauley, Stanislav V. Sokolov, Richard G ComptonAbstract:Nafion sub-micro particles doped with Methyl Viologen (MV2+) are synthesized using the re-precipitation method and characterized by scanning electron microscopy and UV-Vis spectroscopy. The electrochemical behavior of MV2+ incorporated into Nafion particles was investigated at both the ensemble and single particle levels. The charge transferred to single MV-Nafion particles was observed using the nano-impact method and shown to be quantitative. Finally, the charge transferred via individual MV-Nafion particle was substantially enhanced in the presence of permanganate. The mechanism of the catalytic nano-impact reaction of mediated permanganate reduction by single MV-Nafion particle is revealed as proceeding via MV+˙ reduced from MV2+ incorporated in Nafion particles through one electron transfer followed by the reduction of permanganate.
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Methyl Viologen mediated oxygen reduction in ethanol solvent the electrocatalytic reactivity of the radical cation
Journal of electrochemical science and technology, 2013Co-Authors: Qianqi Lin, Christopher Batchelormcauley, Richard G ComptonAbstract:Abstract: The study of Methyl Viologen (MV 2+ ) mediated oxygen reduction in electrolytic ethanol media possesses potential application in the electrochemical synthesis of hydrogen peroxide mainly due to the advantages of the much increased solubility of molecular oxygen (O 2 ) and high degree of reversibility of MV 2+/•+ redox couple. The diffusion coefficients of both MV 2+ and O 2 were investigated via electrochemical tech-niques. For the first time, MV 2+ mediated O 2 reduction in electrolytic ethanol solution has been proved to be feasible on both boron-doped diamond and micro-carbon disc electrodes. The electrocatalytic response is demonstrated to be due to the radical cation, MV •+ . The homogeneous electron transfer step is suggested to be the rate determining step with a rate constant of (1 ± 0.1) × 10 5 M − 1 s − . With the aid of a simulation program describing the EC’ mechanism, by increasing the concentration ratio of MV 2+ to O 2 electrochemical catalysis can be switched from a partial to a ‘total catalysis’ regime.Keywords: Methyl Viologen, mediated oxygen reduction, ethanolic solution, diffusion coefficient and concentration of oxygen, homogeneous rate constant
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use of split waves for the measurement of electrocatalytic kinetics Methyl Viologen mediated oxygen reduction on a boron doped diamond electrode
Physical Chemistry Chemical Physics, 2013Co-Authors: Qianqi Lin, Christopher Batchelormcauley, Richard G ComptonAbstract:The mediated reduction of oxygen via the reduced form of Methyl Viologen is studied voltammetrically. The investigation is facilitated through the use of a boron-doped diamond electrode, allowing the catalytic response to be clearly delineated from that of the direct oxygen reduction process at the electrode surface. From simulation a high homogeneous electron transfer rate (6 × 109 M−1 s−1) is found for the one-electron reduction of oxygen to superoxide. This value is in close agreement with that found using non-electrochemical methods and is significantly higher than the values previously reported in electrochemical studies. In the latter case it is demonstrated that the underestimation of the electron transfer rate arises due to oversimplification of the reaction mechanism.
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laser activation voltammetry selective removal of reduced forms of Methyl Viologen deposited on glassy carbon and boron doped diamond electrodes
Analytical Chemistry, 2000Co-Authors: Fulian Qiu, Richard G Compton, Frank Marken, Shelley J Wilkins, Christiaan H Goeting, John S FoordAbstract:The effect of high-intensity laser pulses on the reduction of Methyl Viologen at glassy carbon electrodes in aqueous solution is investigated using laser activation voltammetry (LAV) under both channel flow and no-flow conditions and compared with the effect of conventional variable-temperature voltammetry. The reduction proceeds in two consecutive one-electron steps, and the neutral two-electron-reduction product of Methyl Viologen is shown by voltammetry and in situ optical microscopy to form two types of deposits, amorphous and crystalline, on the electrode surface. Laser activation voltammetry using a 10 Hz pulsed Nd−YAG 532 nm laser is shown to remove the deposits from the electrode surface at different laser intensities: the amorphous material is more easily ablated than the crystalline deposit. By conventional variable-temperature voltammetry, it is shown that the two stripping peaks disappear as the temperature is increased. However, with conventional heating, the opposite ease of removal is dete...
Roger J Mortimer - One of the best experts on this subject based on the ideXlab platform.
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in situ spectroelectrochemistry and colour measurement of a complementary electrochromic device based on surface confined prussian blue and aqueous solution phase Methyl Viologen
Solar Energy Materials and Solar Cells, 2012Co-Authors: Roger J Mortimer, Thomas S VarleyAbstract:Abstract The fabrication, in situ spectroelectrochemistry and colour measurement of hybrid electrochromic devices (ECDs) based on a surface-confined metal hexacyanometallate – Prussian blue (PB, containing the iron(III) hexacyanoferrate(II) chromophore) – and aqueous solution-phase Methyl Viologen ( N , N ′-diMethyl-4,4′-bipyridylium) are described. In the ECDs, the initial (‘off’) bleached state is set with PB in its reduced form and the Methyl Viologen as the di-cation. Switching to the coloured state (‘on’), forms the mixed-valence iron(III) hexacyanoferrate(II) chromophore upon oxidation of iron(II) hexacyanoferrate(II), with simultaneous reduction of the Methyl Viologen di-cation to form a mixture of the radical cation monomer/dimer. Using the Commission Internationale de l'Eclairage (CIE) system of colorimetry, the colour stimulus of such ECDs and the changes that take place on reversibly switching between the colourless and coloured states have been calculated from in situ visible region spectra recorded under electrochemical control. The concentration of the solution-phase Methyl Viologen and its diffusion to the cathode controlled both the proportion of surface-confined (reduced) PB that is switched to the blue form and the overall ECD changes. For the ECDs' ‘on’ states, the CIELAB 1976 colour space coordinates for a D55 illuminant were L ⁎ =60, a ⁎ =3 and b ⁎ =−46, and L ⁎ =49, a ⁎ =9 and b ⁎ =−59, respectively for 5 and 10 mM Methyl Viologen solution concentrations. The low a ⁎ and high (negative) b ⁎ chromaticity coordinates quantified the overall ECD colour stimulus of the ‘on’ state as being deep blue, with a broad absorption across the visible spectral region. CIELAB 1976 colour space coordinates showed that the ECDs were fully transparent and nearly colourless in the ‘off’ states, with L ⁎ =100, a ⁎ =1 and b ⁎ =1. The changes in the transparency were 83.0% (5 mM Methyl Viologen) and 93.1% (10 mM Methyl Viologen) between the ‘off’ (bleached) and ‘on’ (coloured) states of the ECDs.
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novel color reinforcing electrochromic device based on surface confined ruthenium purple and solution phase Methyl Viologen
Chemistry of Materials, 2011Co-Authors: Roger J Mortimer, Thomas S VarleyAbstract:A novel color-reinforcing electrochromic device (ECD) is described in which the anode and cathode reactions simultaneously exhibit reversible colorless to intense purple changes. Under coloration, the mixed-valence iron(III) hexacyanoruthenate(II) chromophore is formed on oxidation of iron(II) hexacyanoruthenate(II), with simultaneous reduction of the Methyl Viologen dication to form a mixture of the radical cation monomer/dimer. Using the CIE (Commission Internationale de l’Eclairage) system of colorimetry, the color stimulus of such ECDs and the changes that take place on reversibly switching between the colored and colorless states have been calculated from in situ visible spectra recorded under electrochemical control. On ECD color switching, with the excellent color-matching between the two purple states, sharp and reversible changes in the hue and saturation occur, as shown by the minimal hysteresis of the track of the CIE 1931 xy chromaticity coordinates. Extrapolation of the xy track to the color ...
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novel color reinforcing electrochromic device based on surface confined ruthenium purple and solution phase Methyl Viologen
Chemistry of Materials, 2011Co-Authors: Roger J Mortimer, Thomas S VarleyAbstract:A novel color-reinforcing electrochromic device (ECD) is described in which the anode and cathode reactions simultaneously exhibit reversible colorless to intense purple changes. Under coloration, the mixed-valence iron(III) hexacyanoruthenate(II) chromophore is formed on oxidation of iron(II) hexacyanoruthenate(II), with simultaneous reduction of the Methyl Viologen dication to form a mixture of the radical cation monomer/dimer. Using the CIE (Commission Internationale de l’Eclairage) system of colorimetry, the color stimulus of such ECDs and the changes that take place on reversibly switching between the colored and colorless states have been calculated from in situ visible spectra recorded under electrochemical control. On ECD color switching, with the excellent color-matching between the two purple states, sharp and reversible changes in the hue and saturation occur, as shown by the minimal hysteresis of the track of the CIE 1931 xy chromaticity coordinates. Extrapolation of the xy track to the color ...
Guangyi Wang - One of the best experts on this subject based on the ideXlab platform.
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generating power from cellulose in an alkaline fuel cell enhanced by Methyl Viologen as an electron transfer catalyst
Journal of Power Sources, 2014Co-Authors: Mengnan Feng, Pingping Zhang, Guangyi WangAbstract:Abstract In this work, we developed a single-compartment direct cellulose alkaline fuel cell by using nickel foam as the anode and Methyl Viologen as an electron transfer catalyst. The maximum power density of the fuel cell at optimal conditions is 450 mW m −2 . High-performance liquid chromatography detected short-chain aliphatic carboxylic acids in the oxidation products. Using common reed and red algae as fuels, the fuel cell achieved maximum power densities of 295 mW m −2 and 154 mW m −2 , respectively.
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a one compartment direct glucose alkaline fuel cell with Methyl Viologen as electron mediator
Applied Energy, 2013Co-Authors: Xianhua Liu, Mengnan Feng, Miaoqing Hao, Lin Zhang, Yong Zhao, Guangyi WangAbstract:Abstract Glucose is abundant, renewable, non-toxic and convenient as a fuel for fuel cells, but current technologies are unavailable for us to directly oxidize it to obtain energy. Fuel cells using enzymes and micro-organisms as catalysts are limited by their extremely low power output and rather short durability. Fuel cells using precious metal catalyst are expensive for large-scale use. In this work, a one-compartment direct glucose alkaline fuel cell has been developed that use Methyl Viologen (MV) as electron mediator and nickel foam as the anode. The rudimentary fuel cell generates a maximum power density of 0.62 mW cm−2, while the maximum current density is 5.03 mA cm−2. Electro-catalytic activities of MV and the nickel foam in alkaline conditions were studied by cyclic voltammetry. It is indicated that the high performance of the fuel cell is attributed to the combined use of MV and nickel foam. 13C-NMR and HPLC were used to analyze oxidation products of glucose. The result shows that the principal oxidation products are short-chain organic acids indicating deep oxidation of glucose is achieved.
Wang Xuejiang - One of the best experts on this subject based on the ideXlab platform.
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conductometric nitrate biosensor based on Methyl Viologen nafion nitrate reductase interdigitated electrodes
Talanta, 2006Co-Authors: Wang Xuejiang, S V Dzyadevych, Jeanmarc Chovelon, Nicole Jaffrezic Renault, Chen Ling, Xia Siqing, Zhao JianfuAbstract:A highly sensitive, fast and stable conductometric enzyme biosensor for determination of nitrate in water is reported for the first time. The biosensor electrodes were modified by Methyl Viologen mediator mixed with nitrate reductase (NR) from Aspergillus niger by cross-linking with glutaraldehyde in the presence of bovine serum albumin and Nafion® cation-exchange polymer. The process parameters for the fabrication of the enzyme electrode and various experimental variables such as pH, the enzyme loading and time of immobilization in glutaralaldehyde vapor were investigated with regard to their influence on sensitivity, limit of detection, dynamic range and operational and storage stability. The biosensor can reach 95% of steady-state conductance value in about 15 s. Linear calibration in the range of 0.02 and 0.25 mM with detection limits of 0.005 mM nitrate was obtained with a signal-to-noise ratio of 3. When stored in 5 mM phosphate buffer (pH 7.5) at 4 °C, the sensor showed good stability over 2 weeks.