Assoc. Prof. Graham WrightKilmartin, Paul A2007-10-182007-10-181996Thesis (PhD--Chemistry)--University of Auckland, 1996.http://hdl.handle.net/2292/1919Photoelectrochemistry and Spectroscopy of Conducting Polymer Electrodes Paul A. Kilmartin The conductive properties of films of polyaniline, substituted polyanilines, polypyrrole and polythiophene formed on platinum electrodes have been studied using photoelectrochemical, spectroscopic and surface science techniques. Bands due to oxidised and reduced forms of the polymers were monitored using in situ Raman spectroscopy, with polyaniline giving separate bands and polypyrrole showing an apparent shift of the main νCC mode by 35 cm-1 V-1. X-ray photoelectron spectroscopy allowed the elements of the polymers to be quantified into their various oxidation states, particularly through a deconvolution of the N 1s peak. Microscopic mounds of polymer were seen under atomic force microscopy consistent with the extent of polymer growth. The current response to a light flash perturbation on a milli-second time scale provided new information about the conducting polymers. For polyaniline in an insulating state, short-lived photocurrents were observed (less than 1.5 ms), while for polyaniline in a conductive state, longer-lasting photocurrents were observed (greater than 1.5 ms). Prolonged photocurrents indicative of high conductivity were observed up to a pH of 3.7, beyond which only shorter transients were obtained, consistent with previous polyaniline conductivity studies. The transition from conducting to insulating regions at more positive potentials was marked by the appearance of a short-lived cathodic photoresponse, which occurred at more positive potentials as the pH was lowered. Two models are proposed to account for the photocurrents. In the insulating state, the polyaniline film functions as a capacitance, with the fast transients being caused by discharge of surface states. In the conductive state, the prolonged anodic and cathodic photocurrents arise from redox processes with expulsion of solution species. Consistent with these models, polypyrrole showed only cathodic photocurrents (with anion release) and sulfonated polyaniline only anodic photocurrents (release of protons). The stable yellow film of parathiocyanogen (SCN)x formed by oxidation of SCN- at a platinum electrode in warm methanolic solution was studied, and was shown to be insulating and electroinactive, with short-lived photocurrents unless exposed to potentials greater than 1 V. Oxidation of SeCN- in aqueous solutions produced an analogous, though less stable, orange paraselenocyanogen film.Scanned from print thesisenItems in ResearchSpace are protected by copyright, with all rights reserved, unless otherwise indicated.https://researchspace.auckland.ac.nz/docs/uoa-docs/rights.htmThesisCopyright: The authorQ111963976