Preparation Of Semiconductor Nano Materials By Electron Beam Irradiation And Its Properties

Semiconductor nanomaterials have a wide application'in the fields of optics,electrics, magnetism,catalysis and medicine due to their attractive and unique characteristics.The preparation of semiconductor nanomaterials is one of the most important fields among nanomaterial researches.Among preparation methods of nanostructural materials,electron beam irradiation method is one kind of approach that has unique characteristic.Electron beam irradiation method has a number of highly advantageous properties:(I) This one-step method is simple,rapid and convenient;(2) It is carded out at room temperature without any kind of toxic reagents and catalyzers;(3) The structure and morphology of products can be controlled by this method;(4) This method is useful for the mass-production of nano materials.In this dissertation, for the first time we have prepared water-soluble blue.emitting CdSe QDs with high fluorescent quantum yield by electron beam irradiation,which is important to the research of biology labeling.A serial of chalcogenide and metal oxides semiconductor namomaterials have prepa ed by electron beam irradiation.The products have small size and well-dispersed.This method is useful for the mass-production of nano materials.Electron beam irradiation has been used to improve the sensitivity of SnO₂ gas sensors and ZnGa₂O₄ gas sensors.This research is a profitable probe and attempt on the application of radiation chemistry.It is hoped to provide a new reference and guide for the related preparation of other materials in the future.Selecting different complexing agents,for the first time we have prepared two kinds of CdSe semiconductor nanomaterials with different structure and optical properties by electron beam irradiation.Cd(Ac)₂·3H₂O and Na₂SeO₃ were used as the reactants.When ammonia was employed as complexing agents,CdSe nanocrystals with the wurtzite structure had been prepared by electron beam irradiation.CdSe nanoparticles were well dispersed with an average grain size of 10nm.With the increase of irradiation dose,the hexagonal crystal lattice was transformed into cubic lattice.UV-vis-NIR spectrum and photoluminescence spectnan showec the blue shitting compare to the bulk material.Luminescent semiconductor quantum dots(QDs) have applied in biology labeling,which is important to the development of multi-colours biology labeling and clinical diagnostics.Howeves, presently Luminescent semiconductor QDs have prepared in non-aqueous system.Therefore it is very important to systhese water-soluble semiconductor QDs with high fluorescent quantum yield. We improved the previous experiments.Selecting EDTA as a complexing agent as well as a surface modifier,blue-emitting CdSe quantum dots with zinc blende structure have been prepared Quantum dots were monodisperse particles with grain sizes of 2-3 nm.Fluorescent quantum yield was up to 21.63%.The carboxyl of EDTA covered around CdSe quantum dots could combine directly with the amidogen of biology molecule,which made CdSe quantum dots to be used as fluorescent probes in life science research.For the first time PbS,PbSe and SnSe nanocrystallites have been prepared in the present of PVA by electron beam irradiation.Lead acetate and thioacetamide were employed as the reactants,and polyvinyl alcohol as surfactant.PbS particles were prepared rapidly in one-step by electron beam irradiation.Using Se powder and lead acetate as reactants,PbSe nanocrystallite was prepared by electron beam irradiation.The as-prepared PbSe nanocrystalline was cube with an average grain size of 30 nm.Nanocrystalline SnSe with about the grain size of 10 nm was prepared through a reaction between a selenium ethylenediamine solution and Se powder by electron beam irradiation method.The structure,morphology and optical properties of as-prepared materials were characterized by X-ray diffraction(XRD),transmission electron micrograph(TEM),atomic force microscope(AFM),UV-vis absorption spectrum and photoluminescence(PL) spectrum.The effects of the ratio of the concentration of lead acetate to thioacetamide,surfactants and irradiation doses on the preparation of PbS,PbSe and SnSe nanocrystallite were also been discussed.Electron beam irradiation method has been used to prepare metal oxides nano materials.α-Fe₂O₃ nanoparticles and SnO₂ rods have been successful obtained by this method.The thermal stability ofα- Fe₂O₃ nanoparticles was analyzed by DSC-TGA,and the phase transition enthalpy energy difference betweenγ-Fe₂O₃ andα-Fe₂O₃ was calculated.The SnO₂ nanorods sensor was utilized to detect CH₃OH and HCHO concentration.The SnO₂ nanorods gas sensor with good performance had high sensitivity,fast response and recovery,and linear dependence of the sensitivity on the concentration of CH₃OH and HCHO gas.Finally we attempted to study the application of electron beam irradiation in gas sensors.The sensitivity of SnO₂ gas sensors and ZnGa₂O₄ gas sensors was improved by electron beam irradiation method.Results showed that the sensitivity of SnO₂ sensors and ZnGa₂O₄ gas sensors to reductive gases were enhanced with the increase of electron beam radiation dose,while the response-recovery time and working temperature decreased.Mechanism of the improvement of the sensitivity of sensors by electron beam irradiation method was discussed with the adsorption theory on surface.