Synthesis and bioactivity of highly ordered TiO2 nanotube arrays

The highly ordered TiO2 nanotube arrays were fabricated by potentiostatic anodization of Ti foils in fluorinated dimethyl sulfoxide (DMSO). TiO2 nanotube arrays are formed using a 40 V anodization potential for 24 h, with a length of 12 μm, diameter of 170 nm and aspect ration of about 70. The as-prepared nanotubes are amorphous, but can be crystallized as the heat treatment temperature increases. Anatase phase appears at a temperature of about 300 °C, then transforms to rutile phase at about 600 °C. After heat treatment at 500 °C and soaking in SBF for 14d, a thick apatite layer of about 13 μm covers the whole surface of TiO2 nanotube arrays, indicating their excellent in vitro bioactivity, which is mainly attributed to their high specific surface area and the anatase phase.