Graded conducting titanium–iridium oxide coatings for bioelectrodes in neural systems

Abstract

Mixed conducting titanium iridium oxides were synthesised as coatings for electrodes and tested in biological media. The oxides do not passivate the conducting platinum substrate, and add a variable oxidation state to the electrode surface which will prevent radical formation. These oxides are an affordable alternative to the more appropriate iridium oxides, with the added properties of titanium. Stratified stoichiometry and concentration gradients are present on the nanometre scale, and the coating surfaces are enriched with iridium. The charge capacity depends on the amount of iridium and is therefore lower than for pure iridium oxides, while other electrochemical responses are similar to those of IrOx. These materials are an inexpensive alternative to pure precious metal oxides and feature natural segregation on the nanometre scale in thin coatings.