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Preparation of Semiconductor Nano Materials by Electron Beam Irradiation and Its Properties

Author: LiZhen
Tutor: WuMingHong；JiaoZheng
School: Shanghai University
Course: Materials Science
Keywords: Nanometer Semiconductor Electron beam irradiation Optical Properties Gas Sensing Properties
CLC: TB383.1
Type: PhD thesis
Year: 2008
Downloads: 286
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Abstract


Semiconductor nanomaterials exhibit many novel features in the optical, electrical, magnetic, catalytic, medicine has a very broad application prospects. Preparation of semiconductor nanomaterials is one of the hot spots in the field of nanomaterials research. Existing semiconductor nanomaterials preparation complex process demanding conditions, low yield, we Preparation of semiconductor nanomaterials using electron beam radiation. This method has distinct characteristics: simple preparation, can be operated at room temperature, is not a member of any catalyst and toxic reagents, the preparation period is short, the phase of the product, the morphology controllable, can be used for industrial-scale production. In this thesis, the first electron beam radiation method synthetic water soluble having an emission quantum yield of the blue fluorescent CdSe quantum dots, which has important significance in the study of biological markers; first time using electron beam radiation Synthesis a chalcogen compound and a metal oxide semiconducting materials prepared nanocrystalline particles is small, good dispersibility, and the reaction time is short, with industrialized mass production prospects; explore the electron beam irradiation method modified aspects of the sensor member application of electron beam irradiation on the surface conductance sensor gas sensing performance has significantly improved. This study to expand the field of radiation chemistry applications, as well as a new method for the synthesis of other materials and ideas. The main content of the paper is summarized as follows: Cd (Ac) 2 · 3H 2O and Na , 2 SeO 3 source for reaction, for the first time using electron beam radiation prepared CdSe nanocrystals. By selecting a different complexing agent to prepare a crystal type and different optical properties of the CdSe nanocrystals. When ammonia as complexing agent, prepared under the irradiation of the electron beam having a good monodispersity, particle size of about 10 nm, the hexagonal wurtzite type CdSe nanocrystals. With the increase in the dose of electron beam irradiation of polymorphs by hexagonal to cubic transition. UV-visible and fluorescence spectra show that the absorption peaks marked blue shift compared with the corresponding material. Nanostructured luminescent quantum dots for biomarker research and development is of great significance on the multicolor biomarker research and disease diagnostics. However, semiconductor nano-emitting quantum dots most synthetic work is conducted in a non-aqueous system, so that the synthesis of such a light emitting quantum dot can not be directly used for the water-soluble biological systems. The synthesis of water-soluble semiconductor quantum dots with luminescence quantum yields become one of the new research focus. We improved the previous experiment, EDTA as a complexing agent and a surface modifier, the ambient temperature water phase was prepared by electron beam irradiation under a zinc blende type blue fluorescent CdSe quantum dot. The quantum dots have a good monodispersity, particle size of about 2 ~ 3 nm, the fluorescence quantum efficiency of 21.63%. There are preferably water-soluble, the carboxyl group of the surface of the quantum dots of EDTA coated outer end directly with the amino group of the biomolecule combination, can be applied to biological systems as a fluorescent probe. The first time, lead sulfide, lead selenide and selenide Tin Oxide semiconductor materials were prepared by electron beam radiation law. Select thioacetamide as a sulfur source, lead acetate, lead source, the electron beam irradiation step synthesis of lead sulfide nanocrystals. Selenium powder and lead acetate as the raw material, preparation, particle diameter of about 20nm the cubic PbSe spherical Nanocrystalline. Se powder and SnCl 2 · 2H · 2O as raw materials, solvent ethylenediamine as a solvent, the synthesized positive orthorhombic SnSe nanocrystalline particle diameter of about 10nm. X-ray powder diffraction, transmission electron microscopy (TEM), atomic force microscopy characterization of the structure, morphology and optical properties, UV spectra and fluorescence spectra of the prepared product, while a different source of sulfur (selenium), the concentration ratio of the reactants, the surfactant and radiation dose on the structure and morphology of the preparation of nano PbS, PbSe and SnSe while the mechanism of the formation of nanocrystals. The electron beam irradiation method is used in the preparation of the metal oxide nanomaterials. We have successfully prepared α-Fe 2 O 3 nanoparticles and SnO 2 nanorods, and synthetic materials were characterized. Α-Fe 2 O 3 nanoparticles thermal stability test using DSC / TGA, the calculated a γ-Fe 2 O to α-Fe 2 O 3 phase transformation enthalpy change. Preparation of SnO rod diameter range of 40-60 nm, length of 200nm. The preparation of the material into a gas sensor, measuring the SnO bar Gas Sensing Properties. The results show that the SnO rod sensor has a higher sensitivity to formaldehyde and methanol gas, the response time is short, fast response time, exhibit good gas sensing performance. The work in this area has not been reported. Finally, explore the application of electron beam radiation sensors modified. SnO 2 sensors and ZnGa 2 O 4 the sensor gas sensing performance of the electron beam irradiation method. The results show that with increasing irradiation dose electron beam irradiation of SnO 2 sensor and ZnGa 2 O 4 sensor sensitivity improved significantly. The electron beam irradiation can significantly improve the gas selectivity of the sensor, response - recovery characteristics, reduce the sensor working temperature, and the sensor has good stability after irradiation. A modified sensor mechanism of electron beam irradiation. The study shows that the electron beam irradiation on the improvement of the performance of the sensor of the surface conduction type has important significance.

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