[Synthesis and photoluminescent properties of core/shell structure ZnS : Mn/SiO2 nanocrystals]

Mn-doped ZnS nanopatricles synthesized by solvothermal method were successfully coated with SiO2 shells of various thicknesses by hydrolysis reaction of tetraethyl orthosilicate (TEOS). The samples were characterized by X-ray diffraction (XRD), transmission electron microscopy images (TEM), X-ray photoelectron spectroscopy (XPS) and the room temperature photoluminescence (PL) spectra. When the ZnS : Mn nanoparticles were coated with SiO2 shells, an obvious increase in particle size and a clear shell of SiO2 can be observed. The XPS measurement also gave the evidence for the core/shell structure of ZnS : Mn/SiO2 nanoparticles. Because the surface modification effect and the decrease in luminescent centers effect are concurrent in the SiO2 shells, the Mn emission intensity first increased and then decreased with the thickening of the SiO2 shell. The intensity, which attained its maxium at 5 shell thickness, was as 7 times as that for the bare ZnS : Mn nanoparticles.