Synthesis Of Doped Quantum Dots And Investigation Of Optical Properties

The geometry size of Semiconductor nanocrystals(NCs) is smaller than the exciton size of a given material, and it’s energy level structure and optical properties will be decided by the quantum confinement effect.If the shape approximates isotropy or sphere, the semiconductor nanocrystals of this size range are called quantum dots(QDs), which has very important application value in industry. Doping is incorporating impurities or defect in the host lattice of the semiconductor material to control some physical properties, such as optics, electricity, magnetism and so on.Especially in terms of optical properties, doped-QDs not only retain the excellent optical property of intrinsic quantum dots, but also have a larger Stokes Shift, thus avoiding the self-quenching phenomenon caused by the self-absorption. The thermal stability and chemical stability of QDs were greatly improved by doping, and their PL lifetime expanded. In this essay, Ⅱ ~ Ⅵ semiconductor nanocrystals is used as host materials of manganese, silver,gold to synthesize a variety of Luminous doped quantum dots(d-dots) of excellent performance. The following innovative results in the preparation and luminescence mechanism of d-dots research have been achieved:1.Hydrothermal method is used to synthesize water soluble Mn: ZnSe QDs. A higherbandgap ZnS or ZnO materials are deposited on the surface of Mn:ZnSe cores QDs by means of epitaxial growth, respectively. And It is also be proved that under the same condition, Mn:ZnSe/ZnS has better chemical stability and higher PL QY than Mn:ZnSe/ZnO.2. High-quality, pure, and color-tunble Ag:ZnCdS quantum dots(d-dots) can be synthesized. The Ag:ZnCdS/ZnScore/shell d-dots with photoluminescence quantum yield(PL QY) is as high as 58% are constructed in situ by the growth ZnS shell around the core Ag:ZnCdS QDs. Ag: ZnCdS alloy d-dots can be transformed into Ag: ZnCdSSe through simple Se treatment at high temperature.3. Based on the way of co-nucleation doping strategy, a new type of sulfur source precursor is used to synthesize high-quality, pure Ag-doped luminous and color- tunable water-soluble Ag:ZnCdS QDs. Meanwhile, thiourea is used as a kind of lower reaction sulfur precursor to synthesize corresponding Ag:ZnCdS QDs to test the advantage of new source of sulfur in the aspect of chemical synthesis.Also synthesize color-tunable Ag:ZnCdSeS QDs were prepared via different scale of Se and S precursor. Furthermore, higher efficient Ag:ZnCdS/ZnS and Ag:ZnCdSeS/ZnS core/shell QDs can be obtained by in-situ deposition ZnS.4.By using highly active sulfur source, MPA as ligand, and through regulating the Au doping content, the ratios of Zn/Cd,pH,Au:ZnCdS quantum dots was synthesized whose luminous position is adjustable in 495-583 nm. Further, through coating broadbandgap ZnS material effectively eliminate the surface defects, the higher PL QY Au: ZnCdS/ZnS QDs are obtained. Finally the X-ray powder diffraction, transmission electron microscopy(TEM) are used to characterize the structure and morphology.