Laccase-modified gold nanorods for electrocatalytic reduction of oxygen

The multicopper oxidase Trametes hirsuta laccase (ThLc) served as a bioelectrocatalyst on nanostructured cathodes. Nanostructuring was provided by gold nanorods (AuNRs), which were characterized and covalently attached to electrodes made of low-density graphite. The nanostructured electrode was the scaffold for covalent and oriented attachment of ThLc. The bioelectrocatalytic currents measured for oxygen reduction were as high as 0.5 mA/cm(2) and 0.7 mA/cm(2), which were recorded under direct and mediated electron transfer regimes, respectively. The experimental data were fitted to mathematical models showing that when the 02 is bioelectroreduced at high rotation speed of the electrode the heterogeneous electron transfer step is the rate-liming stage. The electrochemical measurement hints a wider population of non-optimally wired laccases than previously reported for 5-8 nm size Au nanoparticle-modified electrode, which could be due to a larger size of the AuNRs when compared to the laccases as well as their different crystal facets. (C) 2015 Elsevier B.V. All rights reserved.