A COMBINED ELECTROCHEMICAL QUARTZ-CRYSTAL MICROBALANCE (EQCM) AND PROBE BEAM DEFLECTION (PBD) STUDY OF A POLY(O-TOLUIDINE) MODIFIED ELECTRODE IN PERCHLORIC-ACID SOLUTION

A combined electrochemical quartz crystal microbalance (EQCM) and prob e beam deflection (PBD) instrument was used to monitor the effects of film history and redox state of an unhydrated poly(o-toluidine) modifi ed electrode immersed in aqueous perchloric acid (pH = 0) solution. Th e degree of film hydration affected the relative contributions of prot ons and anions exchanged during the first redox process and the potent ial of the first anodic voltammetric peak. A distinct proton contribut ion to the ion exchange during the first redox process was detected du ring the second and subsequent cycles. Electroneutrality during the se cond charge transfer step was maintained predominantly by proton expul sion. The determination of the diffusion coefficient of the exchanged species in the first redox process by the time dependence of laser bea m deflection delay and by temporal convolution of the current signal a re compared. The concomitant changes in the gravimetric and optical si gnals during film hydration demonstrate the participation of both prot on and solvent during redox cycling of poly(o-toluidine). (C) 1998 Els evier Science S.A. All rights reserved.