ZnS nanocrystals co-activated by transition metals and rare-earth metals—a new class of luminescent materials

We report on the unique luminescent properties of ZnS nanoparticles co-activated by Cu2+ and rare-earth metallic ions. The co-activated ZnS nanocrystals with varying sizes from 20 to 30 Å have been prepared by using a chemical coprecipitation at room temperature. The nanoparticles can be co-doped with copper and rare-earth metallic ions during synthesis without altering X-ray diffraction patterns. However, the doping shifts the luminescence to 540–550 nm. The fluorescence intensity of the co-activated ZnS nanoparticles is about 10–15 times that of undoped ZnS nanoparticles. These novel properties may be attributed to the formation of composite luminescent centers of Cu and rare-earth metallic ions.