Strong visible-light emission of ZnS nanocrystals embedded in sol–gel silica xerogel

ZnS nanoparticles embedded in novel porous phosphor silica xerogel have been synthesized by sol–gel processing. Their fluorescence properties have been evaluated and compared with those of the Na+-doped and un-doped silica xerogels. Stable and strong visible-light emission of the doped samples has been observed. The relative fluorescence intensities of the samples doped with ZnS nanoparticles (S2− ions have been obtained by the water solution of NaS) are the highest among all of the doped samples. Its relative fluorescence intensity is about 7.5 times of that of the un-doped silica xerogel and about 300 times of that of pure ZnS nanoparticles. The emission wavelength of the ZnS-doped and Na+-doped samples is the same as that of the un-doped silica xerogel and ZnS nanoparticles (λem=440–450 nm). This high efficiency luminescence of the doped silica xerogels has been assigned to the luminescence centers of ZnS nanoparticles and Na+ in the porous phosphorescence silica xerogel.