ZnS∶Co2+ nanocrystals were prepared in aqueous solution by both one-step and two-step methods.The surface of the prepared ZnS∶Co2+ nanocrystals was modified by mercaptoacetic acid(TGA).The UV-vis absorption spectroscopy was employed as a direct probe to detect the location of Co2+ dopant in ZnS∶Co nanocrystals.The transition of Co2+4T1g(F)→4T1g(P)was observed from the ZnS∶Co2+ nanocrystals derived by the one-step sample,and the Co2+ 4A2(F)→4T1(P)transition was detected from the ZnS∶Co2+ nanocrystals derived by the two-step sample.The results indicate that Co2+ existed on the surface instead of in the lattice of ZnS nanocrystals derived by the one-step method.And for those ZnS∶Co2+ nanocrystals by using the two-step method,Co2+ were co-precipitated in the lattice of ZnS nanocrystals.And additionally,the band gap of the lattice co-precipitated doped ZnS∶Co2+ nanocrystals was narrower than the pure ZnS samples.
