A novel cation-binding TiO2 nanotube substrate for electro- and bioelectro-catalysis

When immobilised onto an inert boron-doped diamond substrate, TiO2 nanotubes show electrochemical reactivity due to reversible Ti(IV) reduction, which is very similar to that observed for anatase nanoparticles. Three cationic redox systems, Meldola's blue, Ni2+, and cytochrome c, are immobilised on the TiO2 nanotube surface; the binding ability and the number of binding sites are quantified voltammetrically. Redox proteins, such as cytochrome c, adsorb readily and irreversibly. Well-defined voltammetric signals for the immobilised protein are observed in an aqueous buffer. TiO2 nanotubes are shown to be novel, inert substrates for both inorganic and biological electrocatalysts.