Photoluminescence of Cu+-doped and Cu2+-doped ZnS anocrystallites

ZnS:Cu+ and ZnS:Cu2+ nanocrystallites have been obtained by chemical precipitation from homogeneous solutions of zinc, copper salt compounds, with S2- as precipitating anion formed by decomposition of thioacetamide. X-ray diffraction (XRD) analysis shows that average diameter of particles is about 2.0-2.5 nm. The nanoparticles can be doped with copper during synthesis without altering XRD pattern. However, the emission spectrum of ZnS nanocrystallites doped with Cu+ and Cu2+ consists of two emission peaks. One is at 450 nm and the other is at 530 nm. The absorptive spectrum of the doped sample is different from that of un-doped ZnS nanoparticles. Because the emission process of the Cu+ luminescence center in ZnS nanocrystallites is remarkably different from that of the Cu2+ luminescence center, the emission spectra of Cu+-doped samples are different from those of Cu2+-doped samples. (C) 2002 Elsevier Science Ltd. All rights reserved.