Scientific studies on photocatalysis started about two and a half decades ago. Titanium dioxide (TiO2), which is one of the most
basic materials in our daily life, has emerged as an excellent photocatalyst material for environmental purification. In this review, current
progress in the area of TiO2 photocatalysis, mainly photocatalytic air purification, sterilization and cancer therapy are discussed together
with some fundamental aspects. A novel photoinduced superhydrophilic phenomenon involving TiO2 and its applications are presented.