Cyclic voltammetry and charge accumulation at conducting organic salt enzyme electrodes

Abstract

Cyclic voltammetry has been used to study the accumulation of charge at TTF-TCNQ/glucose oxidase enzyme electrodes. Charge accumulates at enzyme electrodes held at potentials below − 50 mV in the presence of enzyme and substrate. The amount of accumulated charge increases as the holding potential is made more negative, partly because residual oxidation is possible at −50 mV and partly because of the corrosion of TTF-TCNQ electrodes which can release species capable of acting as mediators or enzyme modifiers. Charge accumulation has also been observed at the normal operating potentials of these enzyme electrodes (50 mV/SCE) when the glucose concentration is greater than 5 mM. At low substrate concentrations when the enzyme electrode current is controlled by membrane transport no accumulation is observed, but as the substrate concentration is increased and electrode kinetics become current controlling then charge accumulation is observed and is found to increase with increasing glucose concentration.