The Synthesis And Application Of Cd Se-based And CsPbX₃（x=Cl、Br、I） Quantum Dots

In this paper, we synthesized various QDs with highly pohotoluminescence through the organic method based on the current preparation methods and application of quantum dots. Various CdTe_xSe_1-x cores and CdSe cores were synthesized by adjusting the surface ligand, reaction time and reaction temperature. In order to improve the photoluminescence performance of QDs, we directly deposited Cd_yZn_1-yS shell materials on the CdTe_xSe_1-x cores and CdSe cores, considering lattice mismatch of core-shell QDs. In the process of coating shell, there is a clear red shift of its corresponding emission peaks. Compared to CdTe_xSe_1-x and CdSe cores, the luminescence efficiency of core-shell QDs was greatly improved.In order to make this superior core-shell QDs applied in biological field, these QDs were transferred from oil to water phase by different methods. In the process of the encapsulation of amphiphilic polymers, the surface ligand, the molecular weight of the poly（styrene-co-maleic anhydride）（PSMA） and the size of the QDs dramatically influenced the process of phase transfer. For the QDs with the same size, the PSMA with high molecular weight exhibit a shorter time in the process of phase transfer compared with light molecular weight. The smaller of the QDs, the shorter of the phase transfer time. For SiO₂ shell coating, QDs with different ligands were employed to investige the effects of ligands on the reverse micelles in preparing QDs@SiO₂ nanoparticles. It was found that CdSe/Cd_xZn_1-xS QDs@SiO₂ nanocomposites could keep excellent PL properties even for 24 h incubating with Siha cells, and the average cell viability was more than 90 % after 24 h incubation, which indicating that our prepared composite nanoparticles is potentially applicable for cell imaging in biological systems.The phase transfer of the QDs was carried out through a ligand exchange and inorganic SiO₂ films with QDs were fabricated. This functional sol–gel SiO₂ films with QDs have exhibited high PL brightness, flexibility and stability. By integrating a thin CdSe QD-silica film on a solar cell, the enhanced current demonstrated that thin film can facilitate the continuous development of solar cells.To expand the application of QDs, they can be applied in QD-sensitized solar cell application, TiO₂ films were fabricated with CdSe QDs using mercaptopropionic acid（MPA） as a bifunctional surface modifier. TiO₂ films sensitized by Cd Se QDs have achieved 1.5-fold enhancement in photocurrent compared with pure TiO₂ films, In addition, the photocurrent enhances as the thickness of TiO₂ films increased. The generation and increasement of the photocurrent were explored.We have synthesized monodisperse colloidal nanocubes of inorganic cesium lead halide perovskites（Cs PbX₃, X=Cl, Br and I, or mixed lead halide Cs Pb（Cl/Br）₃ and Cs Pb（Br/I）₃） with brightly luminescent properties using a facile, solution-phase method. The emission wavelength of resulting Cs Pb X₃ quantum dots can be varied from 440 nm to 696 nm by adjusting the amount of different Pb X₂（X=Cl, Br and I）. These Cs Pb X₃ NCs exhibit high quantum yields up to 95 % and narrow emission line widths with 14-35 nm. The injection speed of OA-Cs precursor affects on CsPbI₃ NCs with different morphology, which can be tuned from littery nanoparticles to uniform nanorods. What’s more, adjusting the amount of OA-Cs precursor can obtain Cs Pb Br₃NCs to Cs₄PbBr₆ NCs or a mixture of CsPbBr₃NCs and Cs₄PbBr₆ NCs. and optical properties of these materials have been controlled by varying the composition.