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题名	复合纳米材料和低维纳米材料的软化学法制备与表征
作者	赵启涛
学位类别	博士
答辩日期	2004
授予单位	中国科学院上海光学精密机械研究所
导师	侯立松
关键词	纳米复合材料 低维纳米结构 软化学合成法 溶胶模板法 光谱特性
其他题名	Preparation by Soft Chemistry Method and Characterization of Nanocomposites and Low-Dimensional Nanostructures
中文摘要	本文研究内容包括三部分，一是在反胶束体系中制备了表面修饰的Ag／SiOx纳米复合颗粒，将其分散在溶胶一凝胶形成的TiO2基体中，制备成Ag／SiOx／TiO2纳米复合薄膜，探讨了这种纳米复合颗粒固化成膜后的光谱特性；二是控制金属醇盐的水解和聚合形成溶胶，以此溶胶作为模板合成了Ag纳米线、Au纳米棒以及CdS纳米棒结构；三是采用有机聚合物分子作为控制纳米材料生长的软性模板，通过软化学法合成了一系列具有特定形状和光谱特性的Ag、Au纳米线（棒）和纳米微晶，宽带半导体CdS、ZnS纳米线、纳米棒，以及单晶Se纳米线、纳米针状结构等。通过对材料的合成方法、微观结构和性能的研究，获得了具有理论意义和潜在应用价值的研究结果。在离子型表面活性剂或非离子表面活性剂所形成的反胶束体系中，引入溶胶一凝胶工艺，都成功地合成了氧化硅SIOx表面修饰的Ag纳米颗粒，研究了这种异质纳米材料的结构和光谱特性。氧化硅壳层结构的存在使得Ag纳米材料的特征吸收红移。当这种异质结构固化在TiO2溶胶中形成薄膜后·吸收峰宽化，并随薄膜厚度发生进一步红移现象。首次建立了制备低维纳米材料的溶胶模板法用DMF兼作溶剂和还原剂，以钦酸四丁酷控制水解形成的溶胶为软性模板，以AgNO3或HAucl4·4H2O为起始物，无须采用晶种，在较低温度（-70℃）下合成了结构均匀的银和金纳米线（棒）。同样，以Cd（NO3）2与TAA为起始物，在低温～50℃下合成了CdS纳米棒。研究了这些低维纳米材料的微观结构及光谱特性。结果证明，通过引入乙酰丙酮（AcAc）控制钦酸四丁醋（TBT）水解形成的溶胶分子间网络孔道为这类低维纳米材料提供了有效的生一民模板。采用有机聚合物分子模板控制金属（Ag和Au）纳米靡，的生长，制备了Ag和Au的三角薄片，Au的四边、六边形薄片结构以及Au纳米配I须等纳米结构材料。对这类纳米材料的光谱性能的研究表明，其光谱表现为多重特征吸收。采用800nm钛宝石飞秒激光作用于纳米Ag三角薄片，对于一个边长100nm，厚度IOnm的Ag三角薄片，热效应（△T可达～2000oK）使其发生结构与形状变化，从多面体转变为球形颗粒，从而引起光学性能的明显变化。采用有机聚合物作为控制半导体纳米材料生长的软性模板，还合成了CdS、Zns纳米棒。以聚合物Brij58为模板，控制合成了结构均匀，直径为8～15nm，长度为50一20Onm的CdS纳米棒，合成产物中同时包含多臂（枝状）CdS纳米棒。高分辨电镜（HRTEM）研究表明，大部分CdS纳米棒沿〔002〕晶面生长。激发波长为32Onm，室温下Cds纳米棒的光致发光光谱在～404nm有一峰值，为CdS纳米棒材料中激子或者电子一空穴对结合所产生。用十二硫醇控制合成了ZnS纳米棒，对其结构、光学性能以及ZnS纳米棒的形成机理进行了探讨。激发波长为335nm时，室温下ZnS纳米棒光致发光谱在一520nm处发射峰分裂为两个峰值。不使用十二硫醇时得到的是片状ZnS纳米结构。十二硫醇对对ZnS纳米结构材料形状的影响归因于ZnS不同晶面具有不同表面自由能：γ｛110｝＞γ｛100｝＞γ｛111｝，因而对十二硫醇选择性吸附，从而控制ZnS纳米薄片生长为ZnS纳米棒。引入表面活性剂PVP作为纳米晶生长模板和稳定剂，采用溶剂热还原H2SeO3，制备了一系列单晶Se纳米线、纳米棒和纳米针结构，用透射电镜（TEM）、扫描电镜（SEM）、选区电子衍射（SAED）对其结构性能进行了表征。研究发现，PVP浓度和反应温度对Se纳米结构材料的形态有明显影响。当[PVP]＝0时，溶液中形成的Se为无定形纳米颗粒a-Se，随着PVP浓度的增加，非晶态。a-Se溶解在溶液中产生部分三斜t-Se，由于。a-Se比t-Se具有较高自由能，a-Se便会以t-Se为晶种，经成核作用沉积在t-Se表面，由于t-Se本身具有螺旋型原子排列结构，从而定向生长为一维单晶Se纳米结构。
英文摘要	The research work of this dissertation contains three parts. In the first part we deal with the preparation of silicon oxide-coated Ag nanoparticles and their dispersion into TiO2 sol for the production of Ag/SiOx/TiO2 nanocomposite films, as well as the investigation into the spectral properties of the nanocomposite films. In the second part, we demonstrate that a novel method has been developed to fabricate nanomaterials such as silver nanowires, gold and CdS nanorods using nanoporous templates formed by the controlled hydrolysis and condensation of a titanium alkoxide. The third part involves the controlled-growth of a series of nanostructures and nanocrystallites with specific morphologies and optical obsorption properties, such as silver, gold, CdS and ZnS nanowires or nanorods, using organic polymers as templates via soft chemistry method. The application of this surfactant-assisted method in the synthesis of single-crystalline Se nanowires and other needle-like nanostuctures is also included. By exploiting the synthetic characteristics, microstructures and specific properties of the nanostructures derived from these new approaches presented in this dissertation, a variety of research results possessing theoretical and potential applicable significance have been obtained. Among them, the creative achievements are as follows. An approach has been successfully developed to fabricate silicon oxide-coated silver nanoparticles Ag/SiOx both in ionic surfactant reverse micellar system and in nonionic surfactant reverse micellar systems by introducing the sol-gel process of TEOS into the reaction systems. Studies on the structure and optical absorption properties of the heterogeneous nanostucture indicated that the absorption edge of the Ag/SiOx nanoparticle is red-shifted compared to the uncoated Ag particles. And the UV-vis absorption spectra demonstrated that the plasmon band of the Ag/SiOx/TiO2 nanocomposite film derived by the dispersion of the heterogeneous nanostructure Ag/SiOx embedded in a TiC>2 sol became broad and red-shifted with the increase of film thickness. For the first time, a novel route for controlling the growth of silver nanowires and gold nanorods has been developed via a simple soft chemistry method comprising thermal reduction of the metal(Ag, Au) ions and hydrolysis and condensation of titanium alkoxide(TBT) in the absence of seeds. The nanoporous template formed by the controlled hydrolysis and condensation of TBT in the presence of acetylacetone(AcAc) provides an effective matrix for the growth of low-dimensional nanowires or nanorods using AgNO3 or HAuCLr4H2O as the starting compounds and DMF as the solvent and reducing agent at a lower temperature(~70 ℃). By virtue of this soft-template method, CdS nanorods were also synthesized using cadmium nitrate and thioacetamide(TAA) as starting materials at a even lower temperature(~50 ℃). Measurements including TEM, EDS and UV-vis spectra were carried out to study the microstructures and optical properties of the products. The experimental results show that channels formed in the TiO2 sol provide effective paths for the growth of the nanowires and nanorods. A series of anisotropic metal nanocrystals including silver and gold nanoprisms, hexagonal and quadrangular gold nanoplates, as well as gold nanowhiskers have been fabricated by using organic polymers as templates to control the growth of the metal nanocrystallites, The absorption spectra of the nanostructures indicated that the plasmon band splitted into several peaks different from those displayed by the spherical counterparts. On the silver nanoprisms in aqueous solution using irradiation by a pulsed Ti:Sapphire femtosecond laser at 800 nm induced the shape change of the nanoprisms from triangles into spheres. The photothermal (or optical 'burning') effect makes the temperature rise, AT as high as ~20000 K in the case of silver nanoprism having an average edge length of ~100nm and thickness of ~10nm. It is also reported in this dissertation that well-defined CdS and ZnS nanorods can be synthesized by the controlled growth of semiconductor nanostructures with some surfactants or polymers as soft templates. Uniform CdS nanorods with diameters of 8-15nm and lengths ranging from 50 to 200nm were obtained using Brij58 as the surfactant to confine the lateral growth of CdS nanostructures with the help of bidentate ligand ethylenediamine. Experimental results of high resolution TEM (HRTEM) studies suggest that most of the nanorods prefer to grow along the {002} direction and some multi-armed CdS nanorods also exist in the reaction system. The photoluminescence (PL) spectrum of the CdS nanorods at room temperature with an excitation wavelength of 320nm depicts that the appearance of a strong emission peak at ~404nm can be ascribed to the recombination of excitons and/or shallowly trapped electron-hole pairs. ZnS nanorods were prepared using dodecylthiol as the template to control the growth of ZnS nanorods. The PL pectrum of ZnS nanorods at room temperature with an excitation wavelength of 335nm has a broad band at ~520nm, which splits into two weak peaks. A plausible function of the surfactants dodecylthiol is to kinetically control the growth rates of various faces with the different free energies associated with these crystallographic planes: Y {uo}> Y {ioo}> Y {in}= resulting in the growth of nanostructues along a preferential plane. A new method of fabricating single crystal Se nanowires, nanorods and needle-like nanostructures is also presented in this dissertation using PVP both as a stabilizer and as a molecular template to confine the lateral growth of Se nanocrystallites through the solvothermal reduction of H2SeC>3. The structure and morphologies were characterized by TEM, SEM and SAED. The experimental results show that the concentration of PVP and the reaction temperature play a crucial role in the formation of the crystal morphology. When [PVP]=0, the products would be amorphous nanoparticles. With the increase in the concentration of PVP, a small amount of amorphous Se(a-Se) would dissolve in the refluxed solution and precipitate out as crystalline trigonal nanoparticles, t-Se, then the amorphous a-Se colloids would slowly dissolve into the solution phase due to their higher free energy than t-Se. The selenium dissolved from a-Se colloids could subsequently deposite on the surface of t-Se nanocrystallites (seeds) and grow into uniform crystalline nanowires because of the helical chains of Se atoms contained in the trigonal phase.
语种	中文
内容类型	学位论文
源URL	[http://ir.siom.ac.cn/handle/181231/15386]
专题	上海光学精密机械研究所_学位论文
推荐引用方式 GB/T 7714	赵启涛. 复合纳米材料和低维纳米材料的软化学法制备与表征[D]. 中国科学院上海光学精密机械研究所. 2004.

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