Synthesis Of Green CdSe Core-Shell Quantum Dots With Ultra-Narrow Fluorescence Emission

Colloidal fluorescent quantum dots(QDs)are one of the most popular luminescent materials due to the narrow luminescence peaks,high color purity,strong fluorescence lifetime,high fluorescence quantum yield,and continuously adjustable fluorescence spectrum,which show great application prospects in the fields of lighting,display,laser,and bio-detection.The synthesis of quantum dot materials with high fluorescence quantum yield and good stability is a necessary condition to promote their practical applications.Meanwhile,the rapidly developing quantum dotbased light-emitting diodes and lasers research have an increasing demand for quantum dot fluorescence half-peak width(color purity).In this thesis,we aim to investigate the synthesis control of large-size quantum dots with high quantum yield,narrow fluorescence emission and good stability based on CdSeS and CdSequantum dots by modulating the synthesis factors and designing the shell structure to construct large-size quantum dots with narrow fluorescence half-peak width.1.Synthetic chemistry of CdSeS-based quantum dot system.Red-shifted fluorescence peak positions of CdSeS quantum dots due to increased addition of cadmium stearate precursors during the growth of CdSeS core.Monitoring the growth process of CdSeS nucleation revealed that the main growth process was completed within 5 minutes and the fluorescence peak pattern of quantum dot nuclei was well maintained within 2 hours under high temperature,showing excellent stability.Further,in the regulation of the shell layer growth,it was found that multiple purifications of the CdSeS nuclei to remove the residual precursors in the reaction system were beneficial to the ZnSeS/ZnS shell layer growth;increasing the reaction solvent was beneficial to the uniform adsorption of the precursor material on the quantum dot surface and to the improvement of the overall quality of the core-shell structure quantum dots.Finally,a two-step synthesis of CdSeSbased green quantum dots with narrow fluorescence emission and large size was determined,and CdSeS/ZnSeS/ZnS core-shell structured quantum dots with fluorescence half-peak width of 20 nm and size up to 13 nm were prepared based on this scheme.2.Synthetic chemistry of classical CdSebased quantum dot system.The effects of crystal growth time,reaction ligand type,quantum dot nucleus concentration and shell structure on the growth kinetics of CdSebased core-shell structured quantum dots were investigated in detail.The effects of oleic acid and oleylamine ligands on the growth of the shell layer were investigated in detail,and the presence of oleic acid and oleylamine at the same time could promote the growth of ZnSeshell II layer by adsorption of precursors on the surface of quantum dots.The epitaxial growth of ZnSeS/ZnS can further optimize the fluorescence half-peak width and improve the stability of quantum dots by confining the exciton in the shell layer.The chemical synthesis of CdSeS and CdSequantum dots revealed that the ligand species,the concentration of quantum dot nuclei and the design of the shell structure are the key factors to reduce the fluorescence half-peak width during the growth of the shell layer,which provides the basis for the application of narrow fluorescence emission quantum dots.It provides a material basis for the application of narrow fluorescence emission quantum dots,and also provides a research idea for the chemical synthesis of other narrow fluorescence emission,large size core-shell structure quantum dots.