Carbon monoxide annealed TiO2nanotube array electrodes for efficient biosensor applications

Abstract

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 Ti³⁺ 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 TiO₂nanotube arrays were ascribed to the carbon-doping and the formation of Ti³⁺ defects.