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  • Polymer and Materials Science  (23)
  • Spectroelectrochemistry  (2)
  • 11
    ISSN: 1040-0397
    Keywords: Tafel analysis ; Mass transport ; Flow system ; Chemistry ; Polymer and Materials Science
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: Analytical theory is presented which allows rigorous mass transport-corrected Tafel analysis for the reversible electrode processes (1) 2B ⇄ A2 + 2e- and (2) B2 ⇄ 2A + 2e- occurring at electrodes in flowing systems. Predictions are compared with the conclusions of numerical finite-difference modelling for both wall-jet and channel flow cell geometries. Exceillent agreement is found.
    Additional Material: 3 Ill.
    Type of Medium: Electronic Resource
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  • 12
    ISSN: 1040-0397
    Keywords: Voltammetry ; Ultrasound ; Ascorbic acid ; Dehydroascorbic acid ; Chemistry ; Polymer and Materials Science
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: The effect of power ultrasound on the voltammetric behavior of ascorbic acid and dehydroascorbic acid at a glassy carbon electrode is described. The voltammetric characteristics of both compounds were found to be modified by ultrasonically formed radicals. In the case of dehydroascorbic acid the single sweep voltammogram shows an anodic signal in the presence of ultrasound which probably results from the formation of an oxidizable radical known to be an intermediate of ascorbic acid oxidation. In the case of ascorbic acid pulsed sonovoltammetry is applied and characterized regarding the time dependence of the current decay and the reliability of its analytical performance. The utility of pulsed sonovoltammetry is demonstrated analyzing a pain killer tablet regarding the ascorbic acid content.
    Additional Material: 6 Ill.
    Type of Medium: Electronic Resource
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  • 13
    ISSN: 1040-0397
    Keywords: Spectroelectrochemistry ; Methyl viologen ; Dimerization ; Chemistry ; Polymer and Materials Science
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: A channel flow cell specifically designed for ultraviolet-visible spectroelectrochemical experiments is described. The performance of the cell was characterized using the oxidation of N,N, N′, N′-tetramethyl-p-phenylenediamine in aqueous electrolytes and excellent agreement between theory and experiment was obtained. The technique was applied to study the dimerization rate of methyl viologen radical cations. The mechanistic results confirm that the electrogenerated methyl viologen radical cation dimerizes rapidly in aqueous solution and a previously unknown dimerization rate constant close to 104 M-1 s-1 is reported.
    Additional Material: 7 Ill.
    Type of Medium: Electronic Resource
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  • 14
    ISSN: 1040-0397
    Keywords: Spectroelectrochemistry ; Diffusion coefficient ; Tris(4-bromophenyl)amine ; Chemistry ; Polymer and Materials Science
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: The use of the channel flow cell for ultraviolet-visible (UV-vis) spectroelectrochemical experiments has been developed to determine the diffusion coefficients of electrogenerated species by means of monitoring the transient absorbance response resulting from a potential step at a working electrode immediately upstream of the incident spectrophotometric beam. The technique is applied to measure the diffusion coefficient of tris(4-bromophenyl)amine (TBPA) radical cation in acetonitrile at 25°C. It is shown that the diffusion coefficient of electrogenerated TBPA radical cation (1.64 ± 0.02 × 10-5 cm2 s-1) is very close to that of the parent molecule (1.57 ± 0.03 × 10-5 cm2 s-1).
    Additional Material: 6 Ill.
    Type of Medium: Electronic Resource
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  • 15
    Electronic Resource
    Electronic Resource
    Weinheim : Wiley-Blackwell
    Electroanalysis 8 (1996), S. 913-917 
    ISSN: 1040-0397
    Keywords: Channel electrodes ; Ohmic distortion ; Simulating mass transport ; Chemistry ; Polymer and Materials Science
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: The distortion caused by the ohmic resistance of the solution in a channel electrode experiment has been calculated by combining a three-dimensional finite element approach based on a resistor network, solved by the SPICE program, in an iterative procedure with the backward-implicit finite difference method, for the case of a reversible 1-electron reduction. By this means, the current distribution over the electrode may be calculated taking into account not only the nonuniform potential distribution imposed by the electrolyte resistance but also the alteration to mass transport induced by the potential distribution. The potential-dependent variation in Tafel slope introduced by the ohmic distortion is calculated and is shown to be in close agreement with experimental data obtained from the reversible one-electron reduction of p-chloranil, allowing the practical current range for experimental measurements to be assessed and if necessary extended. The three-dimensional SPICE simulation has also been applied to study the effect of reducing the electrode width to a small fraction of the channel width, when significant current flow to the sides of the electrode will occur.
    Additional Material: 7 Ill.
    Type of Medium: Electronic Resource
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  • 16
    Electronic Resource
    Electronic Resource
    Weinheim : Wiley-Blackwell
    Electroanalysis 8 (1996), S. 30-33 
    ISSN: 1040-0397
    Keywords: Microband electrodes ; Diffusion ; Ultramicroelectrodes ; AC impedance spectroscopy ; Chemistry ; Polymer and Materials Science
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: The AC impedance behavior of microband electrode geometries which deviate from the ideal is derived via numerical modelling of the chronoamperometric response under diffusion-only conditions. Specifically attention is given to four electrode shapes in addition to the ideal microband geometry: elevated microband electrodes (with conducting supporting sides), recessed microband electrodes (with insulating pit walls), platform electrodes (with insulating supporting sides) and, for the purposes of comparison, a hypothetical line electrode without any support which permits diffusional mass transport to both sides of the infinitesimally thin electrode. Simple analytical expressions are established for the frequency dependence of the AC impedance in each case.
    Additional Material: 6 Ill.
    Type of Medium: Electronic Resource
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  • 17
    ISSN: 1040-0397
    Keywords: Anodic stripping voltammetry ; Numerical simulation ; Hydrodynamic electrodes ; Electrode kinetics ; Chemistry ; Polymer and Materials Science
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: The time dependent backwards implicit method is used to simulate the shape and position of the stripping peaks in DC (linear scan) anodic stripping voltammetry at mercury thin film hydrodynamic electrodes for electrochemically irreversible and quasireversible systems assuming that the electrode diffusion layer thickness is uniform, as in the case of a rotating disk electrode. The effect of the electrochemical rate constant in influencing both the peak potential and peak shape is examined and the conditions identified under which electrochemically reversible behavior is approached.
    Additional Material: 7 Ill.
    Type of Medium: Electronic Resource
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  • 18
    ISSN: 1040-0397
    Keywords: Flow electrolysis ; Channel electrode ; Microband arrays ; Chemistry ; Polymer and Materials Science
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: Analytical and numerical methods are used to establish concentration distributions around channel microband electrodes both in isolation and as part of multi-electrode arrays. The importance of axial diffusion in addition to convection and diffusion normal to the electrode surface is stressed. In particular, downstream depletion effects are shown to occur over many electrode lengths, so that the diffusion fields of electrodes within arrays overlap and interfere. A simple analytical expression is derived to describe this depletion and permits the design of practical arrays in which electrodes operate essentially independently of each other.
    Additional Material: 8 Ill.
    Type of Medium: Electronic Resource
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  • 19
    ISSN: 1040-0397
    Keywords: Chemistry ; Polymer and Materials Science
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: The electron transfer between excited-state 9,10-anthracenedione (325 nm) and sodium tetraphenylborate (tetraphenylboron sodium) in acetonitrile solution is shown to form the radical anion of 9,10-anthracenedione together with the BPh4· radical. The latter is known to decompose to biphenyl and other Products. A new channel electrode methodology is developed and characterized to deduce the mechanism of the reaction and to quantify its kinetics.
    Additional Material: 8 Ill.
    Type of Medium: Electronic Resource
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  • 20
    ISSN: 1040-0397
    Keywords: Chemistry ; Polymer and Materials Science
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: The wall-jet ring-disc electrode is shown to provide a convenient means determining homogeneous rate constants by means of ring current measurements as a function of disc currents and electrolyte flow rates. Theory is provided for the analysis of such “collection efficiency” experiments and applied to the specific case of the bromination of anisole, where good agreement with experiment is found. Advantages with respect to the rotating ring-disc electrode are pointed out.
    Additional Material: 7 Ill.
    Type of Medium: Electronic Resource
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