A branched core-shell nanosphere composed of an anatase TiO 2 (a-TiO 2 ) core and a TiO 2 nanobranch shell with gradient-doped N (a-TiO 2 @N-TiO 2 ) is synthesized by a simple in situ doping method, in which mixed crystal anatase-rutile TiO 2 (ar-TiO 2 ) nanosphere is first prepared by oxidizing Ti using H 2 O 2 , and then is etched by NH 3 middotH 2 O to form (NH 4 ) 2 TiO 3 nanobranches, which is converted into a-TiO 2 @N-TiO 2 following an ambient annealing process. The diameter of a-TiO 2 core is similar to 500 nm, and the thickness of NTiO 2 branched shell is similar to 100 nm with gradua...
