High catalytic performance of laccase wired to naphthylated multiwall carbon nanotubes

The direct electrical connection of laccase on the electrode surface is a key feature in the design of efficient and stable biocathodes. However, laccase can perform a direct electron transfer only when it is in the preferred orientation toward the electrode. Here we report the investigation of the orientation of laccase from white rot fungus on multi-walled carbon nanotube surface modified with a naphthalene group. Naphthylated multi wall carbon nanotubes were synthesized and the kinetics of laccase from white rot fungus adsorption and its direct electro-catalytic activity toward oxygen reduction was investigated by QCM and electrochemical techniques. Compared to pristine multi-walled carbon nanotubes laccase shows a high affinity to be adsorbed onto the surface of naphthylated carbon nanotubes at a very fast rate. The subsequent wiring to the naphthylated multi-walled carbon nanotubes is accompanied by a reorientation and arrangement of adsorbed laccase to create a composite biocathode that exhibits a high-performance for oxygen reduction by direct electron transfer with maximum current densities of 3 mA cm^-2.