University of Illinois Urbana-Champaign

I. Luminescence Spectroelectrochemistry in Thin Layer Cells. Ii. Kinetics of Mediated Oxidation at a Polymer Modified Electrode

Jones, E. Tracy Turner

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Description

Title
I. Luminescence Spectroelectrochemistry in Thin Layer Cells. Ii. Kinetics of Mediated Oxidation at a Polymer Modified Electrode
Author(s)
Jones, E. Tracy Turner
Issue Date
1985
Department of Study
Chemistry
Discipline
Chemistry
Degree Granting Institution
University of Illinois at Urbana-Champaign
Degree Name
Ph.D.
Degree Level
Dissertation
Keyword(s)
Chemistry, Analytical
Abstract
  • I. In general, only one member of a redox couple will be luminescent if redox activity and luminescence originate in the same molecular feature. Moreover, diffusion controlled quenching by the nonluminescent form, through energy or electron transfer, is a likely decay route for a long-lived excited state. Thin layer spectroelectrochemical theory for such a system was derived from the Nernst and Stern-Volmer equations. The tris(2,2'-bipyridine) complex of osmium(III/II) in 1.0 M H(,2)SO(,4) was chosen as a test case. The luminescence Os(bpy)(,3)('2+) *, emitted from an optically transparent thin layer electrode, was monitored as a function of potential. As in the absorbance mode experiment, analysis of the data via Nernst plots proved to be an excellent means of determining n and E('o)', despite the intrusion of photochemical processes in the test system. In addition, the luminescence mode experiment was found to be a useful probe of quenching behavior.
  • II. Poly(styrenesulfonate, sodium salt) was spincoated on glassy carbon rotating disk electrodes (RDE's) for use as a matrix for the mediated oxidation of ferrocene-1,1'-disulfonate by electrostatically bound tris(2,2'-bipyridine)osmium(III). This particular mediator-substrate system is designated as case C in the terminology of the Andrieux-Saveant kinetic model for polymer modified electrodes. Case C systems are not catalytic; direct oxidation (reduction) of the substrate precedes oxidation (reduction) of the pre-mediator redox form. However, the existence of two plateau currents facilitates diagnosis of the factors that limit the mediated current. The Andrieux-Saveant theory was applied to voltammetric data obtained at rotating and stationary RDE's and to chronocoulometric data. Analysis of the data revealed that electron self-exchange among the densely packed mediator centers was an efficient process, whereas substrate diffusion through the film was hindered. Mediated oxidation of substrate occurred primarily at the film-solution boundary.
Graduation Semester
1985
Type of Resource
text
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