Synthesis And Characteristics Of The Surface Modification Of Semiconductor Nano-zns Quantum Dots

ZnS semiconductor nanometer quantum dots (QDs) have shown distinguished quantum-size effected optic-electronic characteristics, which promise it a wide application in the future. In this thesis, a route to produce ZnS nanometer QDs is presented with lyothermal colloid growth method, combined with surface derivatization (i.e. capping technique). With zinc acetate and thioacetamide(TAA) as precursors, 1-thioglycerol as capping molecule, ZnS QDs of 2-3nm in diameter was successfully synthesized in aqueous solution at relative low temperature. With water/2-propanol as soluable/insoluable solvents, size-selective precipitation process was applied to the as-grown ZnS QDs. Four samples with different sizes and improved monodispersity were successfully separated from the original reaction solution. Structure and optical characterization were carried out by TEM, XRD and UV-visible obsorption spectra measurement. A tight-binding framework for description of semiconductor QDs was verified by results of our experiment. Attained ZnS QDs sample have shown the maximum blue shift of over 1eV with absorption peak at 261.8nm compared with 339.4nm of bulk ZnS crystal. The solubility of ZnS QDs sample is more than 0.1M, which proves the high dispersity of ZnS with derivatization. In the thesis, the background of our research work is first introduced. A description of lyothermal colloid growth method is presented in the chapter Two with a emphasis on surface derivatization and size-selective precipitation. A explanation of detailed process accepted in our experiment was given in chapter Three. Structure and optical characterization in chapter Four. A detailed description of size-selective process in chapter Five. Finally conclusion and suggestion in the chapter Six followed by reference.