Gold nanoparticles as electronic bridges for laccase-based biocathodes

Abstract

Direct electron transfer (DET) reactions between redox enzymes and electrodes can be maximized by oriented immobilization of the enzyme mols. onto an electroactive surface modified with functionalized Au nanoparticles (AuNPs). Here, the authors present such strategy for obtaining a DET-based laccase (Lc) cathode for O2 electroredn. at low overpotentials. The stable nanostructured enzymic electrode is based on the step-by-step covalent attachment of AuNPs and Lc mols. to porous graphite electrodes using the diazonium salt redn. strategy. Oriented immobilization of the enzyme mols. on adequately functionalized AuNPs allows establishing very fast DET with the electrode via their Cu T1 site. The measured electrocatalytic waves of O2 redn. can be deconvoluted into two contributions. The one at lower overpotentials corresponds to immobilized Lc mols. that are efficiently wired by the AuNPs with a heterogeneous electron transfer rate const. k0 » 400 s-1.