Uniform TiO2 spheres with a size of around 400nm were successfully synthesized by a facile approach from Ti powders. The obtained TiO2 spheres exhibit a good anatase structure ever before the annealing treatment. Through the measurement of UV–Vis spectra and XPS spectra, it was proved that the as-obtained TiO2 spheres contained a lot of oxygen vacancies (Vo). After annealed, the concentration of Vo were decreased seriously. Magnetic measurements showed that the ferromagnetism of the TiO2 spheres also decreased with the annealing treatment, which informed the larger the concentration of Vo was, the stronger the ferromagnetism became. These results indicated that the ferromagnetism in undoped TiO2 could be attributed to oxygen vacancies.

Oxygen Vacancies Contained TiO2 Spheres: Facile Fabrication and Enhanced Ferromagnetism. Li, H., Zeng, Y., Huang, T., Liu, M.: Journal of Nanoparticle Research, 2012, 14[8], 1030-2