Synthesis and photoluminescent properties of core/shell structure ZnS:Cu/ZnS quantum dots

ZnS:Cu quantum dots have been synthesised via a water-soluble route, then the ZnS shell coated for surface modification. The influence of shell thickness on the optical properties of ZnS:Cu quantum dots has been studied. The samples were characterized by TEM, XRD, PL, PLE and UV-Vis. The results showed that the ZnS:Cu/ZnS quantum dots were cubic sphalerite, uniform spherical-shaped and had a narrow size distribution. The average particals size increased from 2 nm to 3.2 nm after the shell modification. The PLE and UV-Vis spectra showed a gradual red shift with the shell thickening, which suggested that the quantum dots was growing with the ns/nc increased. It can proved that the ZnS shell growed on the ZnS:Cu quantum dots surface and formed the ZnS:Cu/ZnS core/shell structure quantum dots. The PL intensity related with Cu2+ increased at the beginning and decreased with further growth of the ZnS shell. The intensity of emission peak achieved the maximum when ns/nc=2.5.