Ultraviolet-enhanced wettability and bioactivity of self-organized TiO ₂ nanotube layer

TiO ₂ nanotube layers were prepared by anodic oxidation of commercial pure Ti in aqueous solutions containing 1 M (NH ₄) ₂SO ₄ and 0.15 M NH ₄F at 20 V for 2 h. The as-anodized layers were annealed at 450°C for 3 h, and a part of the annealed layers were subsequently irradiated by Ultraviolet (UV) light in air for 2 h at room temperature. Hydrophilicity and the apatite-forming ability of TiO ₂ nanotube layers were evaluated. The results show that the as-anodized layer consists of self-organized TiO ₂ 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 TiO ₂ 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 TiO ₂ nanotube layer.