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Structural defects and luminescence of ZnS nanocrystals

Author: ZhangXiaoBo
Tutor: CaoJianLin；SongHongWei
School: Graduate Schoo,Chinese Academy of Sciences
Course: Optics
Keywords: ZnS nanocrystals Light Surface states Phase change Lattice
CLC: O731
Type: Master's thesis
Year: 2004
Downloads: 328
Quote: 0
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Abstract


In this paper, annealing and cleaning experimental means , more in-depth study of the particle size of ZnS nanocrystals , structural phase transition , the particle surface states and luminescence properties , the main contents are as follows : 1 grain size were synthesized by homogeneous precipitation method for 11nm ZnS nanocrystals . With the means of X-ray diffraction and scanning tunneling electron microscopy experiments , research ZnS nanocrystals after annealing size variation with temperature relationship is given with the processing temperature of the particle size to a sharp increase in the temperature range , interpreted from the perspective of energy annealing grain growth reasons . 2 Make sure that the ZnS nanocrystals from cubic phase to monoclinic phase transition critical temperature . The temperature is far lower than the ZnS material of the phase transition temperature of 1020 ° C . With reference to the the CdS nanocrystals melting temperature reported in the literature about 1000K lower than the melting temperature of the corresponding material experimental results , we of ZnS nanocrystals lower phase transition temperature also gives the corresponding explanation . 3 system comparison of the annealing treatment after the ZnS nanocrystals and commercial phosphor photoluminescence intensity . After annealing , the nanocrystalline samples emission spectra Centre is located at 520nm emission bands , while the emission band did not occur in the commercial phosphor samples obtained after the same annealing treatment , we explored its origin . Eu doping greatly enhances the luminous , did not appear trivalent europium luminescence characteristics , given the corresponding interpretation . 4 by changing the frequency of cleaning in the preparation process of the ZnS Nanocrystals , compare the change of the luminous intensity in the before and after washing , analysis of the distribution of self - activated luminescent centers in the nanocrystals , i.e. surface Sites of self - activated luminescent centers tend to occupy . ZnS shot Yi sessions inferior knot hasty Age cavity with hair Fang Shuo inside J shoots frustrations husband Jun Yi play 5 by means of Raman spectroscopy , EPR ( electron paramagnetic resonance ) spectroscopy , and UV irradiation induced spectral changes in experimental means , more in-depth study the the nanocrystalline surface states . Adsorbed on the surface of the nanoparticles OH , CH =; clearly part of these functional groups may act as a self-activated light-emitting donor is one of the main and the role of a COO and other organic functional groups in the donor 's point of view

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CLC: > Mathematical sciences and chemical > Crystallography > Crystal physics > The physical properties of the crystal
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