Sn4+ and S2- co-doped N-TiO2-x nanoparticles for simultaneously efficient photocatalytic removal of multi-contaminants Jiahui He, Jin Ye, Kai Ge, Jiayu Cao, Congcong Fu, Zhenxing Li, Yue Zhang and Yongfang Yang Abstract Abstract: N-TiO2-x nanoparticles (NPs) were selected as a basic construction unit for its plenty of Ti3+ and O vacancies on its surface. When S2- and Sn4+ are co-doped into the N-TiO2-x lattice, the positions of O2- and Ti4+ can be replaced, respectively.