Preparation Of Alloy QDS And The Photocatalysis Of QDS

Semiconductor nanocrystals (quantum dots, QDS) have a number of significant opto-electronic properties. We explored the synthetic methods of different nanocrystals:high quality CdSexTe1-x alloyed quantum dots with near-infrared light-emission, Bi2O3 quantum dots exhibiting excellent photocatalytic activity. The crystallinity, morphology, components and optical properties of the obtained QDs were characterized by powder X-ray diffraction (XRD), transmission electron microscopy (TEM), inductively coupled plasma atomic emission spectrometry (ICP-AES), UV-vis (UV) and photoluminescence (PL) spectroscopy.The main contents in the thesis are as follows:My thesis contains two parts:synthesis of near-infrared-emitting CdSexTe1-xalloyed quantum dots, the photocatalytic degradation activity of a-Bi2O3 QDS.(1) High-quality CdSexTe1-x colloidal nanocrystals were synthesized in a "green" solvent paraffin via a noninjection one-pot approach with the use of cadmium oxide (CdO), elemental selenium, and elemental tellurium as Cd, Se, and Te sources respectively. This features synthetic reproducibility and large-scale capability. The bandgap engineering of the obtained CdSexTe1-x QDs can be conveniently realized through the variation of growth temperature. Red-to near-infrared-emitting (620-780 nm) QDs with nearly identical particle sizes can be obtained when the reaction temperature was changed from 180 to 280℃. The as-prepared CdTeSe QDs exhibit photoluminescence quantum yield as high as 53%.(2) Colloidal oil-soluble Bi2O3 quantum dots (QDs) are first synthesized through an alcoholysis route in organic media. Water-soluble Bi2O3 QDs are obtained from the initial oil-soluble QDs via phase transfer by surface modification with mercaptopropionic acid. The crystallibility is enhanced and particles grow larger after phase transfer. The water-soluble Bi2O3 QDs exhibit excellent photocatalytic activity on degradation of methyl orange in a wide range of pH values. After several cycles, the Bi2O3 QDs still remain high degradation efficiency.