The Study On The CdSe Nanocrystals

CdSe belongs to the II-VI type semiconductors. CdSe nanocrystals have some novel and excellent properties due to the quantum effects. Hence, the synthesis of CdSe nanocrystals is a very attractive research field. CdSe nanocrystals have great application prospects and could be used to fabricate high performance solar cell, quantum dots lasers, biological labels, photovoltage devices and LEDs et al.In this dissertation, we investigated the dependence of CdSe nanocrystals size on the manipulative factors according to the TOP-TOPO-HDA route and found the influence of the dosage of surfactants on the size of the CdSe quantum dots (QDs).A new method was developed to synthesize CdSe nanocrystals. The new solvent A is more environment-friendly and cheaper than the old solvents. The usage of solvent A can slash the cost by 90 percent and make the synthesis obey the principles of green chemistry. Based on this new method, high quality CdSe nanocrystals were synthesized and characterized by UV-Vis, PL, XRD, EDX and TEM, and the size of CdSe QDs could be controlled by adjusting various factors such as the reaction temperature, injection mode, monomers concentration, the ratio between monomers and the ligand concentration et al. The shape control regularities of CdSe nanocrystals was studied both in HDA system and in solvent A, and different shapes such as spheres, rods (wire) and multi-pod et al were obtained.In order to improve the photostability of the CdSe QDs, the surface modification of CdSe QDs via organic and inorganic passivation has been investigated. The CdSe@ZnSe core-shell nanocrystals were synthesized by a one-pot method both in HDA system and in solvent A. A new core-shell-shell type of nanocrystal, CdSe@ZnSe@SiO2, was synthesized via microemulsion method. The double shells make the nanocrystals compatible to aqueous solution which is essential to the biological application.The crystallization of CdSe QDs in TOP-TOPO-HDA system was quantitatively determined and the growth of CdSe QDs was found to be a diffusion-controlled process. A new diffusion-controlled growth model has been developed and the simulation results fitted the experimental data quite well. The crystallization kinetics of CdSe QDs in the new solvent was qualitatively determined. According to population balance model and moving boundary algorithm, the simulation study of the crystallization process of CdSe QDs in solvent A was basically completed.