ELECTROCHEMISTRY AND DETECTION OF SOME ORGANIC AND BIOLOGICAL MOLECULES AT CONDUCTING POLYMER ELECTRODES .3. EVIDENCE OF THE ELECTROCATALYTIC EFFECT OF THE HETEROATOM OF THE POLY(HETETROARYLENE) AT THE ELECTRODE ELECTROLYTE INTERFACE/

The electrocatalytic effect of the conducting poly(3-methylthiophene) film (3-PMT) electrode on the redox behavior of catechol compounds has been examined. The nature of the electrode material substrate had no effect on the peak potentials in the cyclic voltammograms (CVs) of dif ferent redox systems of biological interest: p-aminophenol, dopamine, catechol and ascorbic acid. The nature of the heteroatom of 3-PMT, pol ypyrrole, polyfuran and polyanaline had a very large effect on their e lectrokinetic properties. The adsorption of molybdenum ion results in the blocking of 'the active sites' at the interface, as indicated by t he disappearance of the electrochemical activity of the 3-PMT film ele ctrode. The surface examination by X-ray photoelectron spectroscopy (X PS) of the molybdenum exposed polymer suggests the possibility of a ch emical bonding between the metal ions and the sulfur heteroatom of the polymer surface. The 'apparent' diffusion coefficients D-app were det ermined from the effect of the scan rate dependency of CVs of the cate chol, etc. The results showed that the electron transfer is predominan tly diffusion controlled at the polymer / solution interface and proba bly involves the sulfur heteroatom specifically.