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Structure and Properties of CdS Nanocrystals Synthesized by Direct Thermolysis of Molecular Clusters

Author: LiZhiGuo
Tutor: CaiWei
School: Harbin Institute of Technology
Course: Materials Physics and Chemistry
Keywords: CdS Nanocrystals Quantum dots Nanorods Molecular clusters directly pyrolysis Doping
CLC: TB383.1
Type: PhD thesis
Year: 2009
Downloads: 188
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Abstract

In this paper (Me4N) 4 [S4Cd10-(SPh) 16] molecules cluster as a single-source precursor using direct pyrolysis size controlled CdS quantum dots synthesized hexadecylamine (HDA), studied the reaction conditions growth process of CdS quantum dots investigated to clarify the mechanism of the reaction; using the molecular clusters as precursors in a single surfactant systems were successfully prepared CdS nanorods with the quantum confinement effect of reaction conditions on CdS Nanocrystalline morphology of law, revealing the formation mechanism of the CdS nanorods; on this basis, the use of inorganic ion exchange effect of the molecular clusters molecular clusters (Me4N) 2 [Co4 (SC6H5) 10] and (Me4N) 4 [S4Cd10 (SPh) 16] as the precursor synthesized Co-doped CdS quantum dots and nanorods to study the influence of Co doping on the the CdS nanocrystalline structure and performance and growth process. The study found that using of molecular clusters directly pyrolysis prepared CdS quantum dots wurtzite structure, morphology rules, high crystallinity, showing obvious quantum size effect, and has a strong fluorescence emission. As the reaction temperature increases in the growth process of CdS quantum dots, quantum dot particle size increases gradually, the change can be divided into two stages: the lower the temperature, CdS particle size of the slow growth of quantum dot nucleation process dominant; the reaction temperature is increased to above 190 ℃ of CdS particle diameter increases rapidly with increasing temperature, quantum dots to enter the stage of rapid growth. With the extension of the reaction time, particle size of the CdS quantum dot is gradually increased, and its size distribution with the reaction narrowing. CdS quantum dots, in the growth process of nucleation and growth of the two separate phases, the two phases in a single solvent system, to achieve the automatic separation. The method is simple, controlled, mild reaction conditions, can be high yield CdS quantum dot (gt; 10 g / L). The test results show that the prepared CdS nanorods morphology uniform size distribution is narrow, and an aspect ratio of about 9:1; nanorod growth along the c-axis, for the wurtzite structure. CdS nanorods exhibit quantum confinement effect and has a larger the Stoke displacement phenomenon. Morphology of CdS nanocrystals with the reaction conditions change, the single source precursor concentration played a decisive role in the morphology of the CdS Nanocrystals product of low concentrations of quantum dots, the straight chain nanorods higher concentrations, high concentration of branched nanorods. Preparation of uniform nanorods reaction concentration of precursor in the synthesis of quantum dot concentration more than twice. Increase the reaction temperature and longer reaction time are conducive to the formation of CdS nanorods. If prepare a uniform, the CdS nanorods having a large aspect ratio, the reaction temperature should be 190 ℃, the reaction time should be more than 5h. The formation of CdS nanorods follow directional adsorption mechanism, reaction driving force dipole attraction, the morphology of the CdS nanocrystals depends on the relationship between the dipole attraction and steric hindrance. Co doped CdS quantum dots (CdS: Co) for near-spherical particles, uniform morphology, a narrow size distribution, high crystallinity, the structure of the wurtzite structure. The Co ion doped CdS lattice Internal CdS: Co quantum dots with room temperature ferromagnetism. CdS: Co quantum dots exhibits quantum confinement effect, a slight red shift of the fluorescence peaks relative to CdS quantum dots. The precursor pyrolysis, by increasing the concentration of the precursor of the molecular clusters successfully prepared Co-doped CdS nanorods Co in CdS doped promote the formation of one-dimensional rods and shorten the reaction time.

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