ZnO quantum-dots (QDs) capped with Cd were synthesized in dilute water-free solution with PVP K30 as a stabilizer and thiourea as a surface modification agent. The samples were characterized by UV absorption spectra, fluorescence emission spectra, Infrared spectra (IR), Transmission electron microscopy (TEM) and X-ray diffraction (XRD). The effects of optimization of matrix and the thiourea concentration on the optical properties of ZnO QDs were studied. The effects of Eu, Li doping on the optical properties of ZnO:Cd was also studied. The results showed that the fluorescence intensity of quantum dots increased obviously after the matrix optimized by doping Cd and doping Eu, Li. It maked particle size distribution more uniform, the grain size more smaller, the main peak blueshift and the yield of quantum dots increase with the use of the thiourea. The XRD peaks of the sample were the broad scattering peaks, and belonged to amorphous form. NH₂ and C—NH₂ stretching vibration absorption peaks were 3189.0 and 1088.2 cm^－1 in infrared spectra as a result of thiourea. The best concentration of thiourea was 32 mg/mL. This method was simple, quantum dots prepared by this method obtained good stability and strong fluorescence intensity. The approach introduced in this paper laid a solid foundation for the biological markers and applications of the quantum-dots.

Key words: ZnO, Cd doping, thiourea modification, the fluorescence intensity, blueshift