ZnS Nanopowders and ZnS/Ag2S Heteronanostructures: Synthesis and Properties

Zinc sulfide ZnS nanopowders were prepared by chemical deposition from aqueous solutions of zinc nitrate and sodium sulfide in the presence of sodium citrate or Trilon B. ZnS/Ag2S heteronanostructures were prepared by two-step chemical codeposition of zinc and silver sulfides. The prepared ZnS nanopowders had average particle sizes ranging from 2 to 10 nm depending on the reagent concentration ratio in the batch. The nanoparticle sizes in the thus-prepared heteronanostructures were 8–10 nm. The diffuse reflectance spectra of nanostructured ZnS and ZnS/Ag2S heteronanostructures were measured. The bandgap width Eg in the studied sulfide nanostructures was assessed based on an examination of the measured optical absorption spectra. As the nanoparticle size decreased from 10 to 2 nm, the Eg in ZnS nanopowders increased in the range 3.59–3.72 eV. The increasing Ag2S percentage in ZnS/Ag2S heteronanostructures leads to narrowing of the bandgap. Pulsed cathodoluminescence (PCL) spectra were recorded. The luminescence characteristics of ZnS and ZnS/Ag2S depend on the preparation method and nanoparticle morphology.