Carbon monoxide annealed TiO2 nanotube array electrodes for efficient biosensor applications†

Highly ordered titania nanotube (TNT) arrays fabricated by anodic oxidation of titanium foil followed with O2 and CO annealing were employed as matrices for the immobilization of horseradish peroxidase (HRP) and thionine chloride (Th) for biosensor application. The influence of annealing gases on TNT crystallinity, morphology, surface chemistry, and electrochemical properties were investigated by means of X-ray diffraction (XRD), scanning electron microscopy (SEM), photoelectron spectroscopy (XPS), and cyclic voltammetry. The results showed that TNT arrays annealed in CO consisted of Ti defects with carbon-doping and exhibited well defined quasi-reversible cyclic voltammetric peaks, indicating enhanced electron transfer and electrical conductivity. When immobilized with HRP and Th, the TNT electrodes were used to sense hydrogen peroxide (H2O2) as investigated by means of UV-Vis absorption spectroscopy, cyclic voltammetry, and amperometry. The results indicated that the biosensor based on a TNT array electrode annealed in CO possessed greatly enhanced properties compared to the as-grown and the O2-annealed TNT array electrodes. The improved biosensor properties of the TiO2 nanotube arrays were ascribed to the carbon-doping and the formation of Ti 3+ defects.