Preparation And Characterization Of ZnTe/ZnSe Quantum Dots

Optical properties of quantum dots depend on their size. Comparing with the traditionalorganic dyes, the distribution of quantum dots fluorescence emission spectra is symmetricaland width is narrow. Also, single-wavelength excitation, high photochemical stability,difficult to photolysis, quantum dots is an excellent selection of new fluorescent probes.Comparing to the series quantum dots of cadmium （CdX，X=Te，Se，S）, series quantum dotsof zinc （ZnX, X=Te,Se,S） is low toxicity. And, luminous band of ZnTe QDs is relativeredshift to ZnSe QDs. Surface of single quantum dots have a lot of defects, and low stability.Core-Shell quantum dots can increase the stability and improve the luminescence properties.In this paper, method of aqueous synthesis is adopted. With ZnSO₄7H₂O and Te powderas raw material. Using NaHTe （or NaHTe） and Zn²⁺as Te （or Se） and Zn precisor,glutathione （GSH）, which as a stabilizer, aqueous synthesized ZnTe, ZnSe and ZnTe/ZnSeQDs. Study the effect parameter of component ration, pH value, temperature, time etc on thespectra of UV absorption and fluorescence of quantum dots, examine the optimal synthesisconditions for quantum dots, characterize their crystal structure and morphology structure.The results show that quantum dots with adjustable optical properties and size can beprepared by changing component ration, pH value of solution, temperature and time ofsynthesis etc parameter. With the increase ratio of anion precursor, UV absorption andfluorescence of ZnTe and ZnSe QDs red shift, and blue shift to ZnTe/ZnSe QDs. The threekinds of quantum dots can be prepared by synthesis in pH rang of pH≥7. With the increase ofpH value, UV absorption peak and emission peak of ZnTe and ZnSe QDs both red shift, butsize inhomogeneity of ZnTe/ZnSe QDs. ZnTe and ZnTe/Znse QDs are hexagonal crystal,ZnSe QDs is sphalerite-type structure, and ZnTe/ZnSe QDs have good properties ofdispersion and fluorescence. When the synthesis condition is Zn: GSH: E（E=Te, Se）=2:4:0.5，pH=7，T=80℃, ZnTe QDs have narrow UV absorption peak and red shift abviously;ZnSe QDs have good stability. Adopted Se: Te=20:1, the same optimal synthesis condition,ZnTe/ZnSe QDs have the best range of fluorescence, and with the reaction time to get goodgrowth, flurescence red shift. The size of prepared quantum dots is about10nm.