pH-Sensitive syringaldazine modified carbon ceramic electrode for bioelectrocatalytic dioxygen reduction

Voltammetrically stable water insoluble 3,5-dimethoxy-4-hydroxybenzaldehydrazine (syringaldazine) modified electrode was obtained by sol–gel processing of methyltrimethoxysilane based sol with dissolved syringaldazine together with dispersed graphite particles. This silicate carbon ceramic electrode exhibits stable voltammetry corresponding to the surface confined oxidation–reduction process. The pH dependence of the immobilized syringaldazine redox potential obeys the Nernst equation in the range of 3–10. After further modification with extracellular lyophilized laccase from Cerrena unicolor encapsulated within a thin hydrophilic silicate film the electrode exhibits catalytic activity towards dioxygen reduction. Both catalytic current and potential are pH dependent.