Microstructure and superhydrophilicity of anodic TiO₂ films on pure titanium

The superhydrophilicity of TiO₂ prepared by anodization of pure titanium was investigated and the underlying mechanism was explored. The water contact angle of the as-anodized oxide decreases with the conversion voltage and ultraviolet (UV) light illumination, whereas the annealed oxide exhibits further low contact angles regardless of the conversion voltage and UV illumination. The O 1s X-ray photoelectron spectroscopy spectra of the oxides have a shoulder peak due to adsorption of hydroxyl groups and the intensity of the peak increases with annealing and UV illumination; these observations suggest that the interaction between the surface of the oxide and the hydroxyl groups is enhanced.