Self-organized highly ordered TiO2 nanotubes in organic aqueous system

A simple method to achieve self-organized, freestanding TiO2 nanotube array was constructed, free of corrosive etching process which was traditionally employed to separate TiO2 nanotubes from the metallic Ti substrate. The TiO2 nanotube arrays were constructed through potentiostatic anodization of Ti foil in aqueous electrolyte containing NH4F and ethylene glycol. The nanotubes in the array were of 45 μm lengths and 100 nm average pore diameters. The effect of NH4F concentration on the length of the self-organized nanotube arrays was investigated. Electrochemical and spectroscopic measurements showed that the as-prepared nanotubes possessed large surface areas, good uniformity, and were ready for enzyme immobilization. The as-prepared nanotube arrays were amorphous, but crystallized with annealing at elevated temperatures, as demonstrated by X-ray diffraction (XRD).