Carbon Nanotubes Derivatized with Mediators for Laccase Catalyzed Oxygen Reduction

The construction of nanostructured biocatalytic electrode for the reduction of dioxygen to water is described. The novelty of the approach relies in the application single-walled carbon nanotubes (SWCNTs) covalently modified with redox mediator 2,2-azinobis-(3-ethylbenzothiazoline)-6-sulfonate) (ABTS) to communicate electronically the laccase active sites with the electrode. The nanotubes were modified either at the ends/defect sites or on the side walls. The ABTS moiety was connected with the nanotubes by the sulfonamide bond, which did not disrupt its electrochemical activity. The population of ABTS at the electrode surface was significantly larger when derivatization of the nanotubes was carried out at the walls. On the other hand, highest catalytic efficiency per mole of ABTS groups available at the electrode was achieved when SWCNTs were derivatized at the ends. This indicates that in the latter case, the conductive properties of the nanotubes play important role in the final catalytic activity of the nanostructured surface.