CATALYTIC REDUCTION OF BENZOQUINONE AT POLYANILINE AND POLYANILINE ENZYME FILMS

The enzyme-mediator-conducting polymer model provides a convenient charge transporting immobilization matrix for redox enzymes in potential biosensor constructions. This study considers the charge transport mechanism in the benzoquinone (Q)-polyaniline (Pani) system. An enhanced current can be obtained on Pani, compared with Pt, using Q as enzyme mediator. Two-electron redox pathways are available for the Q/H-2Q (hydroquinone) system, but the kinetics limit this conversion. On Pt, one-electron equivalent is estimated. On Pani-modified electrodes, reduction of Q on Pani is a nearly reversible two-electron process at stationary electrodes at low pH. At rotating electrodes, the initial reaction occurs at the surface of the polymer at pH 1.1, but the second electron transfer is prevented by loss of the intermediate from the surface before it can migrate into the film. At stationary electrodes, the H-2Q product is stabilized, possibly by the formation of a charge-compensating complex between the H-2Q anion/radical and the polymer, At higher pH, charge transfer through the polymer is slow and no reduction of Q occurs on the outside of the film, instead occurring in a layer at the electrode limited by the exchange kinetics there. Promotion of the two-electron pathways on Pani is proposed as the source of current enhancement when Q is employed as an enzyme mediator.