Ultraviolet-enhanced wettability and bioactivity of self-organized TiO2 nanotube layer

TiO₂ nanotube layer was prepared by anodic oxidation of commercial pure Ti in aqueous solutions containing 1M (NH₄)₂SO₄ and 0.5 wt% NH₄F. The as-anodized layer consists of self-organized TiO₂ nanotubes with amorphous structure, which transforms to anatase after annealing at 450 °C for 3 h. The annealing treatment of the nanotube layer can significantly enhance its hydrophilicity and bioactivity. Furthermore, UV irradiation of the annealed TiO₂ nanotube layer does not alter its surface morphology and phase component, however, can improve hydrophilicity and bioactivity. The enhanced hydrophilicity and bioactivity are thought to result from the abundant basic Ti-OH groups on the UV-irradiated TiO₂ nanotube layer.