Impact of TiO 2 Reduction and Cu Doping on Bacteria Inactivation under Artificial Solar Light Irradiation.

Preparation of TiO ₂ using the hydrothermal treatment in NH ₄ OH solution and subsequent thermal heating at 500-700 °C in Ar was performed in order to introduce some titania surface defects. The highest amount of oxygen vacancies and Ti ³⁺ surface defects were observed for a sample heat-treated at 500 °C. The presence of these surface defects enhanced photocatalytic properties of titania towards the deactivation of two bacteria species, E. coli and S. epidermidis, under artificial solar lamp irradiation. Further modification of TiO ₂ was targeted towards the doping of Cu species. Cu doping was realized through the impregnation of the titania surface by Cu species supplied from various copper salts in an aqueous solution and the subsequent heating at 500 °C in Ar. The following precursors were used as a source of Cu: CuSO ₄ , CuNO ₃ or Cu(CH ₃ COO) ₂ . Cu doping was performed for raw TiO ₂ after a hydrothermal process with and without NH ₄ OH addition. The obtained results indicate that Cu species were deposited on the titania surface defects in the case of reduced TiO ₂ , but on the TiO ₂ without NH ₄ OH modification, Cu species were attached through the titania adsorbed hydroxyl groups. Cu doping on TiO ₂ increased the absorption of light in the visible range. Rapid inactivation of E. coli within 30 min was obtained for the ammonia-reduced TiO ₂ heated at 500 °C and TiO ₂ doped with Cu from CuSO ₄ solution. Photocatalytic deactivation of S. epidermidis was greatly enhanced through Cu doping on TiO ₂ . Impregnation of TiO ₂ with CuSO ₄ was the most effective for inactivation of both E. coli and S. epidermidis .