Oxidation–Reduction Dynamics in Layer-by-Layer Self-Assembled Redox Polyelectrolyte Multilayer Modified Electrodes

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Abstract:

The oxidation–reduction dynamics of layer-by-layer (LbL) self-assembled redox polyelectrolyte multilayer films on electrodes has been studied by cyclic voltammetry, chrono-amperometry, electrochemical quartz crystal microbalance (EQCM), ellipsometry, and Fourier transform reflection-absorption infrared spectroscopy (FT-IRRAS). Thin layer electrochemistry with fast electron transfer at the underlying metal-film interface and charge propagation by electron hopping between adjacent redox sites in the finite thin film has been observed. An almost ideal cyclic voltammetry for a fixed number of redox sites in the thin surface film suggests that the multilayer can be fully oxidized and reduced in the time scale of the experiment (RT/vF ≥ 0.05 sec). The electron hopping diffusion coefficient 3 × 10−10 cm2 s−1 was obtained from the chronoamperometric current transient and the ellipsometric thickness. Both cyclic voltammetry and potential step yield a surface osmium bipyridyl redox concentration of ΓOs = 4 × 10−10 mol·cm−2 for (PAH-Os)5(PVS)4 film. Exchange of ions and solvent occur simultaneously to the charge injection as revealed by the EQCM mass change and the ellipsometric thickness change. From the end-to-end mass-to-charge linear relationship, the molar mass of the ionic and neutral species exchanged largely exceeds the molar mass of any ions or solvent which suggests an important flux of solvent during redox switching. An initial "break in" effect is observed for the first oxidation–reduction cycles when a newly self-assembled film equilibrates with the electrolyte as charge is injected during the electrochemical perturbation.

Keywords: ELLIPSOMETRY; EQCM; LAYER BY LAYER; OSMIUM BIPYRIDYL; REDOX POLYELECTROLYTE; SELF-ASSEMBLED

Document Type: Research Article

DOI: http://dx.doi.org/10.1166/jnn.2006.237

Publication date: June 1, 2006

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  • Journal for Nanoscience and Nanotechnology (JNN) is an international and multidisciplinary peer-reviewed journal with a wide-ranging coverage, consolidating research activities in all areas of nanoscience and nanotechnology into a single and unique reference source. JNN is the first cross-disciplinary journal to publish original full research articles, rapid communications of important new scientific and technological findings, timely state-of-the-art reviews with author's photo and short biography, and current research news encompassing the fundamental and applied research in all disciplines of science, engineering and medicine.
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