CONTROLLING PROCESSES IN THE RATE OF CHARGE TRANSPORT THROUGH [OS(BIPY)2(PVP)NCL]CL REDOX POLYMER-MODIFIED ELECTRODES

The rate of homogeneous charge transport through [Os(bipy)2(PVP)(n)Cl]Cl films (25 greater-than-or-equal-to n greater-than-or-equal-to 5), has been examined using potential-step methods and cyclic voltammetry (bipy = 2,2'-bipyridyl, PVP = poly(4-vinylpyridine). The effect of redox site loading, electrolyte concentration and temperature on D(CT), the charge-transport diffusion coefficient for homogeneous charge transfer within the immobilised film for the Os(II/III) oxidation, has been investigated in hydrochloric and perchloric acids. The relevant activation parameters enthalpy, entropy, free energy changes and activation energy for homogeneous diffusional charge transport are presented. These studies reveal that the rate-determining step is dependent not only on the redox site concentration and electrolyte composition but also on the experimental timescale. These observations are considered in relation to the physico-chemical properties of the immobilised layers on the homogeneous charge-transport properties.