Synthesis and Properties of ZnS Quantum Dots by an Oil-Water Interface Method

Nowadays, novel synthesis routes of nanoparticles are attracting a considerable attention of relative scientists. In this work, monodispersed spherical ZnS quantum dots (QDs) were synthesized by an oil-water interface method. The as-prepared products were characterized by X-ray diffraction (XRD), transmission electron microscopy (TEM), and high-resolution transmission electron microscopy (HRTEM). Typical TEM images showed that the average size of ZnS QDs was 3.3 nm. The ZnS QDs with the largest yield and UV absorbance were obtained with the mole ratio of [S²⁻]/[Zn²⁺] = 1.2/1.0 at 100 °C. Based on the above results and the previous outstanding work for synthesis of monodispersed inorganic nanoparticles, the formation mechanism of the monodispersed ZnS quantum dots was proposed. Additionally, UV-vis absorption and photoluminescence (PL) spectra for Mn²⁺ and Eu³⁺ doped ZnS QDs were used to investigate their optical properties. Effects of Mn²⁺ and Eu³⁺ doping ratio on their optical properties were studied. The optimized doping ratio of Mn²⁺ and Eu³⁺ was 4.0 mol.% and 5.0 mol.%, respectively.