| Quantum dots with excellent luminescent properties and optical stability, such as size tunable, narrow and symmetric fluorescence emission spectra, broad and continuous absorption spectra, the anti-photo bleaching and so on, not only can serve as a durable marker imaging materials used in biomedical fields, but also for light hair color diodes, flat panel displays, quantum lasers, solar cells, water treatment, etc., which attract the physical, biological, chemical experts in various fields dedicated to the study of quantum dots.Preparation of quantum dots is divided into the organic phase and the aqueous phase. Recently, ZnSe quantum dots with a non-Cd and other toxic metals have been synthesized in the organic phase of emitting blue fluor. Organic-phase synthesis and stable ZnxCd1-xSe quantum dots, can adjust the maximum fluorescence emission wavelength in blue-green area by changing the molar ratio of Zn2+/Cd2+, but the size of oil-soluble quantum dots are too large, besides, these oil-soluble quantum dots can not be directly applied in vivo and the post-processing of surface modification affects the fluorescence quantum yield of oil-soluble quantum dots. In this paper, we do the major research on preparation of stable ZnSe quantum dots and ZnxCd1-xSe quantum dots with light-emitting area of the blue-green region in the aqueous phase, and experiment consists of the following three parts:1. Chosen glutathione (GSH) as ligand in experiment, ZnSe quantum dots with stable optical properties were prepared by optimizing the pH, temperature, molar ratio of Zn: GSH:Se, reflux time of the precursor and we make parallel reaction for discussing the grow mechanism of ZnSe quantum dot; as well as discussions of aerobic and anaerobic reaction on fluorescence properties under ultraviolet irradiation; the particle size and' internal structure of these quantum dots are determined by XRD patterns and TEM images.2. Based on the first part of the synthesis of high quality ZnSe quantum dots, ZnxCd1-xSe quantum dots are prepared via adding to appropriate amount of CdCl2. Regulating Cd2+/Zn2+ molar ratio of ZnxCd1-xSe quantum dots, their PL peak positions are tunable in a broad range from 410-470nm with narrow bandwidths(fwhm=35～40nm). When the Cd2+/Zn2+ molar ratio of 0.8, by observation UV absorption and fluorescence emission spectra of ZnxCd1-xSe quantum dots under different reflux time, we discussed formation mechanism of ZnxCd1-xSe quantum dot and carry out XRD and TEM characterization of quantum dot sizes to be about 2nm. Without any post-processing fluorescence quantum yield increased to 16%.3. The use of N-acetyl-L-cysteine (NAC) as the ligand for synthesizing a series of high-quality green-blue-emitting NAC-capped ZnxCd1-xSe quantum dots via a one-pot route. As a derivative of L-cysteine, NAC has a better biocompatibility and good water-solubility than GSH and L-cysteine, is user and environmentally friendly,, inexpensive and nonvolatile. The fluorescence emission spectra range of 410-510nm,. half-peak width of 35-40nm can be tuned by changing the composition of the ZnxCd1-xSe quantum dots. The post UV irradiation of these quantum dots improved their fluorescence properties, resulting in stronger emission. These ZnxCd1-xSe quantum dots can be keep in the refrigerator for several months does not precipitate, indicating that quantum dots with good optical stability.
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