X-ray Absorption Spectroscopy, X-ray Diffraction and Optical Luminescence Studies of Phase Transition of Titania Nanotubes

Lu Yao, The University of Western Ontario

Abstract

The one-dimensional (1D) TiO₂ nanotubes (NTs) and their derivatives have been extensively studied due to their wide applications, such as photocatalysts, solar cell, paints and so on. Since TiO₂ has a wide band gap (~3.0 eV), its photo-absorption as the photocatalyst only occurs in the UV region that wastes mostly solar energy. Therefore, the solution to higher photocatalytic efficiency has been sought for some time. This thesis presents a study of the size-dependent phase transitions of TiO₂ NTs using synchrotron-based X-ray techniques. The chemical environment including local symmetry and the luminescence origin of the TiO₂ NTs can be tracked by X-ray absorption near-edge structures (XANES) and X-ray excited optical luminescence (XEOL) technique. As a result, the anatase-to-rutile transition highly depended on the sizes of NTs with the same annealing treatment. Additionally, the shortest NTs require a lower temperature to start the amorphous-to-anatase transition.