Synthesis And Characterization Of Water-Soluble Luminescent Quantum Dots

Quantum dots (also known as colloidal semiconductor nanocrytals,QDs)are generally composed of II-VI and III-V elements, which exhibit strongly size dependent optical and electrical properties. Highly quality semiconductor nanocrystals have shown potential applications in thin film light-emitting devices, non-linear optical devices, solar cells and life science. Quantum dots synthesized by organometallic approach have high quantum yield,sharp emission spectra, monodispersity and good crystallinity. However, key chemicals used in this route are toxic, expensive, pyrophoric, and even explosive. In this thesis,we synthesized a series of quantum dots in aqueous solution using thiols as the stabilizers.This method is simple and controllable; the as-prepared quantum dots show good optical properties. The main contributions are as follows:1. CdTe/CdSe core-shell quantum dots (QDs) were synthesized in water phase using thiolglycolic acid ( TGA ) as stabilizing agent under microwave irradiation. The influence of microwave irradiation and a series of experimental variables, including heating temperature, molar ratios and concentration of precursors on the synthesis of QDs were investigated systematically. The results of high-resolution transmission electron microscopy (HRTEM) and X-ray diffraction (XRD) showed that the as-prepared nanocrystals had the core-shell structure and good water solubility.2. Water-soluble CdTe/ZnTe core-shell quantum dots (QDs) were synthesized using glutathione (GSH) as stabilizer. The effects of molar ratios of Zn/Cd and Zn/GSH on the optical property of QDs were investigated by fluorescence spectroscopy. The morphology and crystal structure of the obtained QDs have been characterized by high-resolution transmission electron microscopy (HRTEM) and power X-ray diffraction (XRD). In comparison with the plain CdTe QDs, both photoluminescence quantum yield (PLQY) and photoactivity of the CdTe/ZnTe core-shell QDs have been greatly improved.3. Water-soluble CdTe QDs are synthesized using two stabilizers (GSH and MPA). The effects of different molar ratios between GSH and MPA on growth rate, optical properties of as-prepared CdTe QDs were investigated. Using both GSH and MPA as stabilizing agents can make quantum dots of high optical properties. The synthesized CdTe QDs possess free carboxyl and amino groups, which were successfully conjugated with Brcaa1 for delivery to gastric cell MGC803, demonstrating that they can be easily bound bimolecularly and have potentially broad applications as bioprobes.