Polystyrene (PS) microspheres were synthesized by emulsion-free polymerization. Based on the PS microspheres template, PS/TiO₂ (core/shell) microspheres were prepared through sol-gel nanocoating using ammonia/triethanolamine as a catalyst system. The N-doped anatase hollow TiO₂ microspheres were obtained after calcinations of the PS/TiO₂ microspheres. Triethanolamine played an important role in the preparation of the hollow TiO₂ microspheres. It was an inhibitor of the sol-gel process, as well as an N source of the N-doped hollow TiO₂ microspheres. The effects of the amounts of ammonia, triethanolamine and tetrabutyl titanate on the morphology and size of TiO₂ shells were investigated, respectively. The surface of the PS/TiO₂ microspheres became smooth with increasing the amounts of triethanolamine or decreasing the amounts of ammonia. Thicker TiO₂ shells were achieved when increasing the amounts of tetrabutyl titanate. The content of N doping in the hollow TiO₂ microspheres could be easily adjusted by varying the amounts of triethanolamine. In addition, the N-doped hollow TiO₂ microspheres possessed the optical response to the visible light and presented photocatalysis under visible light.

Key words: PS/TiO₂ microsphere, nitrogen doping, hollow TiO₂ microsphere, morphology, visible light