Synthesis and photoluminescence of well-dispersible anatase TiO2 nanoparticles.

High-purity anatase TiO(2) nanoparticles were prepared using a low-temperature sol-gel route. The as-prepared sample was characterized by X-ray diffraction, transmission electron microscopy, infrared spectroscopy, thermogravimetric analysis, UV-vis spectroscopy, and photoluminescence. It is shown that the as-prepared sample crystallized in a pure anatase phase with an average crystallite size of about 7 nm, and the surfaces were highly hydrated. These nanoparticles were stabilized as a water suspension via the cooperation of DLVO force and surface hydration force. These suspensions showed characteristic band-gap emission at 397+/-1.5 nm, which is a little red-shifted compared with the band-gap energy of indirect electronic transition measured in the UV-vis absorption spectrum. These observations were explained by the light-induced relaxation of polar water molecules in the surface hydration layer.