【作者】 李珍；

【导师】 吴明红； 焦正；

【作者基本信息】 上海大学 ， 材料学， 2008， 博士

【摘要】 半导体纳米材料呈现出许多新奇的特性,在光学、电学、磁学、催化、医药等方面具有极为广阔的应用前景。半导体纳米材料的制备是纳米材料研究领域的热点之一。现有的半导体纳米材料制备方法存在着工艺复杂、条件苛刻、产率低等问题,我们采用电子束辐射法制备半导体纳米材料。该法具有鲜明的特点:制备工艺简单,可在常温下操作,不加入任何催化剂和有毒试剂,制备周期短,产物的物相、形貌可控,可用于工业规模生产。在本论文工作中,首次采用电子束辐射法合成了水溶性具有发光量子产率高的蓝色荧光CdSe量子点,这在生物标记研究中具有重要的意义;首次采用电子束辐射法合成了一系列硫族化合物和金属氧化物半导体纳米材料,制备的纳米晶颗粒细小、分散性良好,反应时间短,具有工业化大规模生产的前景;探索了电子束辐射法在传感器件改性方面的应用,电子束辐照对表面电导型传感器的气敏性能有明显的改善。本研究拓展了辐射化学应用的领域,同时也为其它材料的合成提供了新的方法和思路。本论文主要内容归纳如下:以Cd（Ac）₂·3H·2O和Na₂SeO₃为反应源,首次采用电子束辐射法制备了CdSe纳米晶。通过选择不同的络合剂,制备出晶型和光学性能不同的CdSe纳米晶。当以氨水作为络合剂,在电子束辐照下制备了具有良好的单分散性,粒径约10 nm的六方纤维锌矿型CdSe纳米晶。随着电子束辐照剂量的增加,晶型由六方型逐渐向立方型转变。紫外可见光谱和荧光光谱表明,与相应的体材料相比其吸收峰发生了明显蓝移。纳米发光量子点用于生物标记研究中,对多色生物标记研究和疾病诊断学的发展具有重要意义。但是目前半导体纳米发光量子点的合成工作大多数是在非水体系中进行的,从而合成的这类发光量子点不能直接用于水溶性的生物体系研究中。因此合成水溶性具有发光量子产率高的半导体纳米量子点就成为新的研究热点之一。我们对前面的实验进行了改进,选择EDTA为络合剂和表面修饰剂,在电子束辐照下室温水相中制备了闪锌矿型的蓝色荧光CdSe量子点。量子点具有良好的单分散性,粒径约2～3 nm,荧光量子效率达21.63%。有较好的水溶性,量子点表面包覆的EDTA外端的羧基能直接与生物分子的氨基相结合,可以作为荧光探针应用于生物体系。首次采用电子束辐射法分别制备了硫化铅、硒化铅和硒化锡纳米半导体材料。选择硫代乙酰胺为合适的硫源,醋酸铅为铅源,采用电子束辐射法一步合成了硫化铅纳米晶。以硒粉和醋酸铅为原料,制备了粒径约为20nm球形的立方PbSe纳米晶。以Se粉和SnCl₂·2H·2O为原料,溶剂乙二胺为溶剂,合成了粒径约为10nm正斜方晶系的SnSe纳米晶。采用X射线粉末衍射、透射电镜、原子力显微镜、紫外光谱和荧光光谱对所制备的产品进行了结构、形貌和光学性能的表征,同时研究了不同的硫（硒）源、反应物浓度比、表面活性剂和辐照剂量对制备纳米PbS、PbSe和SnSe的结构和形貌的影响,同时提出了纳米晶形成的机理。将电子束辐射法应用于金属氧化物纳米材料的制备。我们成功地制备了α-Fe₂O₃纳米颗粒和SnO₂纳米棒,并对合成的材料进行了表征。采用DSC/TGA测试了α-Fe₂O₃纳米颗粒热稳定性,计算了γ-Fe₂O₃向α-Fe₂O₃相转化的焓变。制备的二氧化锡纳米棒直径范围40-60 nm,长度200nm。将制备的材料制作成气敏元件,测量二氧化锡纳米棒的气敏性能。结果表明,二氧化锡纳米棒传感器对甲醛和甲醇气体有较高的灵敏度,响应时间短,而且回复时间快,表现出良好气敏性能。这方面的工作未见文献报道。最后探索了电子束辐射法在传感器件改性方面的应用。研究了电子束辐照法对SnO₂传感器和ZnGa₂O₄传感器气敏性能的影响。结果表明,在电子束辐照下,随着辐照剂量的增加,SnO₂传感器和ZnGa₂O₄传感器的灵敏度显著提高。电子束辐照能显著提高传感器的气体选择性、响应—恢复特性、降低传感器的工作温度,且辐照后的传感器有较好的稳定性。讨论了电子束辐照改性传感器机理。研究表明电子束辐照对表面电导型传感器的性能的改善具有重要意义。更多还原

【Abstract】 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.更多还原