Structure control and its influence on photoactivity and phase transformation of TiO₂ nano-particles

Nanocrystalline titania (nominally TiO₂) has received great attention in recent years due to its unique dielectric, optical and catalytic properties. Photocatalysis is being exploited for the destruction of water and airborne organic pollutants. Properties influencing photocatalytic activity of titania particles include surface area, crystallinity, crystallite size and crystal structure. In this study, the properties of titania are systematized with respect to thermal history and processing parameters. Methods are described to manipulate polymorphic phase transformations and photoactivity of nanocrystalline TiO₂ powders synthesized by a sol-gel route. The characteristics of the materials were investigated using HRTEM, XRD Rietveld refinement, and UV-Vis spectrometry and correlations drawn between structure, crystallite size, chemical composition and photoactivity. The quantum size effect was observed in the size-controlled nanocrystalline TiO₂ particles.