Study On Synthesis And Surface Photoelectron Characteristics Of ZnO Nanocrystals

In this thesis, ZnO quantum dots with high dispersion and uniform particle size were synthesized by liquid phase method. A series of research on the synthesis of ZnO quantum dots were carried out. Firstly, the ZnO quantum dots(QDs) were synthesized by three different kinds of sulfhydryl compouneds, which were TG, TGA and MPA, respectively. The main impact factors were the zinc concentration, the mole ratio of zinc hydroxide material, zinc and ligand material ratio, reaction temperature and reflux time. Then Ag doped ZnO was synthesized. The response variable followed by the amount of zinc concentration and zinc hydroxide material ratio, the doping content of Ag, reaction temperature and reflux time. The optimal scheme of ZnO QDs was determined by intensity of the surface photovoltage of the sample according to the orthogonal experiment design.The ZnO QDs synthesized under the optimal conditions were characterized by XRD. And the particle size of the sample was calculated by Scherrer formula. The results show that the ZnO quantum dots are hexagonal structure, and the average particle size is between 3nm and 7nm. The microstructure of the quantum dots was characterized by transmission electron microscopy, high resolution transmission electron microscopy and electron diffraction pattern. The results show that the synthesized samples are polycrystalline. EDS energy spectrum was used to analyze the samples. The results showed that the ZnO and Ag doped ZnO samples were all spherical quantum dots, and The ZnO QDs of the ligand modified are core-shell structures of the Zn O/ZnS/ ligand. The UV-Vis absorption spectra, fluorescence spectra and surface spectra of the samples were tested. It is found that the wave of UV-Vis absorption spectra are complementary to the fluorescence spectra. The three kinds of surface modifiers make the grain refining, which makes the absorption and emission peaks blue shift; Ag doping makes the grain coarsening, which makes the absorption and emission peaks red shift; In addition, compared with the pure Zn O QDs, the surface photovoltage spectra of the modified Zn O QDs is broadened, which shows that the surface electron transition behavior of the quantum dot is affected by the ligand modification and doping.The test and analysis of the field induced surface photovoltage spectra of ZnO quantum dot are carried out. The influence and mechanism of different polarity and intensity of electric field applied to the surface of the sample is discussed.