钛基纳米结构的制备和性能研究

<正>纳米结构材料因其特殊的性能和潜在的应用前景而成为目前科学研究中的一大热点.基于纳米结构材料的光学、电学和机械特性强烈依赖于其形态和维度;基于“自下而上”原理构建纳米器件的关键问题在于合理控制器件中构筑单元的均一性,可控合成具有特定形貌和维度的纳米结构材料具有非常重要的科学和实用意义.本论文以钛基纳米结构材料为研究对象,探索了其不同异形体的制备方法,并研究了其性能.主要研究内容和结果如下:     

无机纳米晶的形貌调控及生长机理研究

形貌及尺寸规整可控的纳米晶体的合成是目前十分引人注目的纳米材料研究领域．制备合成中的形貌调控及其功能化是这些纳米材料能够得到应用的关键问题．研究者们希望在纳米晶的任一阶段均能实现控制并在期望的阶段停止,从而得到尺寸、形态、结构及组成确定的纳米晶体．本文综述了近年来无机纳米晶体的典型合成路径,深入探讨了纳米晶在成核、生长及熟化阶段的控制原理,研究了液相合成纳米材料过程中晶体结构与生长行为的相关性问题,并总结了几类具有代表性的低维、多维纳米晶体的形成规律和生长机理．探索纳米粒子的调控合成对于纳米材料的规模化生产及应用具有重要的理论价值和指导意义．     

新型核壳结构水凝胶的合成与表征

以羟丙基纤维素为模板,在水溶液中合成了不含表面活性剂的聚甲基丙烯酸（PMAA）纳米水凝胶。再以该PMAA纳米水凝胶为模板,合成了具有pH和温度双重敏感的聚甲基丙烯酸/聚N-异丙基丙烯酰胺（PMAA-PNIPA）核壳结构纳米水凝胶。对纳米水凝胶的形态、结构、pH以及温度敏感性的表征结果表明,纳米水凝胶粒径为338.8～407.9 nm,并随交联剂用量的增加而减小,其体积相转变具有良好的pH及温度响应性,这种绿色合成的生物相容性新型核壳结构纳米水凝胶具有极为广泛的应用前景。     

微孔分子筛纳米晶的控制合成及其催化应用

纳米分子筛因具有高的外表面积和短的孔道结构而显示了独特的催化活性和选择性, 近年来已成为催化界的研究热点.本文就分子筛纳米晶的控制合成、催化基础研究,特别是当前分子筛纳米晶在自组装分级多孔材料和分子筛基纳米复合材料方面的新方向进行了系统的综述,分析了纳米分子筛研究中的机会和应用前景.     

具有特殊浸润性的各向异性微纳米分级结构表面构筑的研究进展

自然界存在许多具有各向异性表面结构的生物,其表面表现出典型的对液体操控的方向性的差异。近年来,这种表面微结构的构筑引起了广泛的研究兴趣,已成为一个热点研究方向。天然的各向异性浸润表面是由复杂的异质微纳米结构组成,基于基础研究和应用推广的目的,可以将其简化为一些有序的方向性结构表面。本文介绍了现在应用广泛的几种各向异性微纳米分级结构的构筑方法,并对比分析其可行性。同时,文中还深入讨论了各向异性微纳米分级结构表面对于液体行为的调控。这种各向异性微纳米分级结构表面在微流体运输、微流控芯片等领域将有重要应用,也会对生命科学(比如生物芯片和重大疾病的早期诊断)、能源(比如电极材料的可控制备)和环境(比如污染物的分离及定向转化)等研究做出巨大的贡献。     

单分散球状纳米金颗粒的合成*

综述了近年来单分散球状金纳米颗粒的合成研究进展。分析了球状单分散金纳米颗粒的应用前景,介绍了单分散球状金纳米颗粒的主要合成方法如种子生长、回流熟化、尺寸选择沉淀分级以及电泳法等,评述了各种方法的优缺点。最后提出了单分散球状金纳米颗粒合成的一些问题,并展望了单分散球状金纳米颗粒的研究和发展方向。     

具有各向异性微纳米分级结构表面的构筑及其特殊浸润性的研究进展

自然界存在许多具有各向异性表面结构的生物,其表面表现出典型的对液体操控的方向性的差异。近年来,这种表面微结构的构筑引起了广泛的研究兴趣,已成为一个热点研究方向。天然的各向异性浸润表面是由复杂的异质微纳米结构组成,基于基础研究和应用推广的目的,可以将其简化为一些有序的方向性结构表面。本文介绍了现在应用广泛的几种各向异性微纳米分级结构的构筑方法,并对比分析其可行性。同时,文中还深入讨论了各向异性微纳米分级结构表面对于液体行为的调控。这种各向异性微纳米分级结构表面在微流体运输、微流控芯片等领域将有重要应用,也会对生命科学(比如生物芯片和重大疾病的早期诊断)、能源(比如电极材料的可控制备)和环境(比如污染物的分离及定向转化)等研究做出巨大的贡献。     

氨基酸辅助合成多种形貌纳米材料的研究进展

氨基酸等生物大分子作为一种特殊的表面活性剂,在合成特殊形貌纳米材料方面具有很大的应用潜力.本文综述了使用多种氨基酸辅助合成的不同形貌的纳米材料,包括一维纳米材料、雪花状纳米结构、三维纳米球等,并对生物科学和化学学科间的交叉发展进行了展望.     

铂纳米晶的形状控制合成及应用

形状控制的铂纳米晶由于具有高选择性和催化活性,近年来受到越来越多的关注。各种低指数晶面所围成的铂纳米晶,包括立方体、四面体、八面体、枝状晶体等可以通过胶体法或热解法来制备。表面具有高指数晶面结构的二十四面体等多面体也已经由电化学方法得到。本文评述了形状控制的铂纳米晶的合成方法、表征和应用等方面的进展,分析了铂纳米晶稳定性的影响因素,并对目前铂纳米晶合成及应用研究中存在的主要问题和发展前景进行了探讨和展望。     

纳米片层结构MFI分子筛的合成及应用

纳米片层结构MFI分子筛因其开放的骨架结构、大的外表面积、适宜的表面酸性、易接触的活性位点和优异的分子传质扩散性能,在吸附、分离、催化等领域展现出良好的应用前景,成为MFI分子筛控制合成及其应用研究的前沿。本文系统总结了纳米片层结构MFI分子筛合成及其应用领域的最新研究进展,重点讨论了原位合成法和后处理法形成纳米片层结构MFI分子筛的合成机理、模板剂种类,深入分析了影响纳米片厚度、片层间距及有序性的因素,提出开发经济成本低、可用于大规模生产纳米片层结构MFI分子筛,并将其应用于制备超薄分子筛膜、催化有机大分子反应、制备片层分子筛负载金属催化剂是未来的主要研究方向。     

Synthesis and Morphogenesis of Organic and Inorganic Polymers by Means of Biominerals and Biomimetic Materials

We have studied the simultaneous synthesis and morphogenesis of polymer materials with hierarchical structures from nanoscopic to macroscopic scales. The morphologies of the original materials can be replicated to the polymer materials. In general, it is not easy to achieve the simultaneous synthesis and morphogenesis of polymer material even using host materials. In the present work, four biominerals and three biomimetic mesocrystal structures are used as the host materials or templates and polypyrrole, poly(3‐hexylthiopehene), and silica were used as the precursors for the simultaneous syntheses and morphogenesis of polymer materials. The host materials with the hierarchical structure possess the nanospace for the incorporation of the monomers. After the incorporation of the monomers, the polymerization reaction proceeds in the nanospace with addition of the initiator agents. Then, the dissolution of the host materials leads to the formation and morphogenesis of the polymer materials. The scheme of the replication can be classified into the three types based on the structures of the host materials (types I–III). The type I template facilitates the hierarchical replication of the whole host material, type II mediates the hierarchical surface replication, and type III induces the formation of the two‐dimensional nanosheets. Based on these results, the approach for the coupled synthesis and morphogenesis can be applied to a variety of combinations of the templates and polymer materials.     

The Synthesis and Application of the Mesoporous Molecular Sieves MCM-41 — A Review

We report a “delayed neutralization” process for the preparation of highly-ordered aluminosilicate MCM-41 molecular sieves with high thermal and hydrothermal stability, and sharp pore size distribution. However, the structural order and pore size are dependent on the carbon chain length. In the mixture surfactant systems, the pore size of the MCM-41 materials could be fine-tuned. The pore size can be extended from 2.5 to 4.5 nm by adding a suitable amount of hydrocarbons. The tubular morphology of the MCM-41 material of 0.3 to 10 micrometers diameter, where the wall consists of coaxial cylindrical pores of nanometers MCM-41, can be obtained by careful control of the surfactant-water content and the rate of condensation of silica. An optimum condition for automatic synthesis of the hierarchical TWT structure has been accomplished. The addition of 1-alkanols as cosurfactant would not only improve the order of the MCM-41 hexagonal structure but also promote the formation of micrometer-sized hierarchical materials, for example: tubules-within-tubule and uniform-sized hollow spheres of diameter 5.0 ± 1.0 μm. However, the inside of the micron spheres has intricate structures possessing various topological genus ranks. The MCM-41 is a good supporter for Molybdenum oxide catalysts. The rate of deactivation in the catalytic reaction of ethyl-benzene dehydrogenation to styrene increases in the order: M_T < M_P < SiO₂. The physically mixed samples have higher catalytic activity than impregnated ones.     

A Hierarchical MFI Zeolite with a Two‐Dimensional Square Mesostructure

A conceptual design and synthesis of ordered mesoporous zeolites is a challenging research subject in material science. Several seminal articles report that one‐dimensional (1D) mesostructured lamellar zeolites are possibly directed by sheet‐assembly of surfactants, which collapse after removal of intercalated surfactants. However, except for one example of two‐dimensional (2D) hexagonal mesoporous zeolite, no other zeolites with ordered 2D or three‐dimensional (3D) mesostructures have been reported. An ordered 2D mesoporous zeolite can be templated by a cylindrical assembly unit with specific interactions in the hydrophobic part. A template molecule with azobenzene in the hydrophobic tail and diquaternary ammonium in the hydrophilic head group directs hierarchical MFI zeolite with a 2D square mesostructure. The material has an elongated octahedral morphology, and quaternary, ordered, straight, square channels framed by MFI thin sheets expanded along the a–c planes and joined with 90° rotations. The structural matching between the cylindrical assembly unit and zeolite framework is crucial for mesostructure construction.     

Synthesis and Characterization of Cu Decorated Zeolite A@Void@Et-PMO Nanocomposites for Removal of Methylene Blue by a Heterogeneous Fenton Reaction

Hydrothermal synthesized nano zeolite A has been encapsulated with ethyl bridged periodic mesoporous organosilica(Et-PMO) shell tlirougli a simple modified Stober method and an organosilane-directed growth-induced etching strategy, the obtained yolk-shell structured A@Et-PMO nanocomposite(YS-A@Et-PMO) was further functionalized by the impregnation of copper ions, realizing the composite material with hierarchical porous and catalytic properties. The morphology and metal content of the Cu/A and Cu/YS-A@Et-PMO were fully characterized. As compared to tlie parent material, the composite Cu/YS-A@Et-PMO has an efficient adsorption and catalytic degradation performance on methylene blue(MB), the removal efficiency reached as high as 95% of 60 mg/L MB within 10 min. These novel structured porous composites may have great potential application for the removal of organic dye including waste effluents.     

Synthesis and Applications of SAPO-34 Molecular Sieves

Silicoaluminophosphate zeolite (SAPO-34) has been attracting increasing attention due to its excellent form selection and controllability in the chemical industry, as well as being one of the best industrial catalysts for methanol-to-olefin (MTO) reaction conversion. However, as a microporous molecular sieve, SAPO-34 easily generates carbon deposition and rapidly becomes inactivated. Therefore, it is necessary to reduce the crystal size of the zeolite or to introduce secondary macropores into the zeolite crystal to form a hierarchical structure in order to improve the catalytic effect. In this review, the synthesis methods of conventional SAPO-34 molecular sieves, hierarchical SAPO-34 molecular sieves and nanosized SAPO-34 molecular sieves are introduced, and the properties of the synthesized SAPO-34 molecular sieves are described, including the phase, morphology, pore structure, acid source, and catalytic performance, in particular with respect to the synthesis of hierarchical SAPO-34 molecular sieves. We hope that the review can provide guidance to the preparation of the SAPO-34 catalysts, and stimulate the future development of high-performance hierarchical SAPO-34 catalysts to meet the growing demands of the material and chemical industries.     

Self-Assembly of Hierarchical Microstructures and Their Ring Patterns in Evaporating Droplets

Urchin-like and tree-shaped hierarchical microstructures were prepared within a solution droplet through drying-mediated self-assembly of organic molecules. The hierarchical architectures inside the droplet can orderly arrange into irregular ring patterns. The morphology evolvement of the hierarchical microstructures and the formation of the ring patterns were captured and studies with the assistance of optical microscopy. Their formation mechanisms were discussed on the basis of the results of time-dependent experiments. The amount of organic molecules in the solution had an obvious effect on the size and morphology of hierarchical microstructures and ring pattern formation. The optical properties of the hierarchical microstructures were investigated in detail and the formation of self-assembled structures resulted in significant changes in optical properties. The formation of the complex superstructures and generation of the ring patterns not only enriched synthesis science but also provided new blocks in future architectures of functional devices.     

Shape Control of VO2 (B) Hierarchical Nanostructures

A green route is designed to gain a clear idea of growth mechanism of complex VO₂ (B) hierarchical microstructures, since this kind of metal oxide has various metastable phases due to their diverse valence states. Three‐dimensional (3D) uniform flower‐like VO₂ (B) hierarchical microstructure has thus been assembled with the interleaving nanoplates, which are about 25 nm in thickness and well‐crystallized in structure with {114} planes as the dominant surfaces. Results of the systemic control experiments revealed that formation of the flower‐like VO₂ (B) results from a fast nucleation‐growth process, where ethylene glycol (EG) not only acts as a green solvent and reductive agent, but also plays a key role in self‐assembly of the resulted VO₂ (B) hierarchical microstructures. Hydroxyl amount on the solvent molecule is crucial in formation and shape control of VO₂ (B) hierarchical microstructures. Result of this work would be helpful to understand the growth mechanism of complex three‐dimensional hierarchical superstructures of different metal oxides, which is very important to material science and inorganic synthetic chemistry.     

Direct Dual‐Template Synthesis of MWW Zeolite Monolayers

A two‐dimensional zeolite with the topology of MWW sheets has been obtained by direct synthesis with a combination of two organic structure‐directing agents. The resultant material consists of approximately 70 % single and double layers and displays a well‐structured external surface area of about 300 m² g^?1. The delaminated zeolite prepared by means of this single‐step synthetic route has a high delamination degree, and the structural integrity of the MWW layers is well preserved. The new zeolite material displayed excellent activity, selectivity, and stability when used as a catalyst for the alkylation of benzene with propylene and found to be superior to the catalysts that are currently used for producing cumene.     

预先负载原料法合成ZSM-5/SAPO-5复合分子筛

采用预先负载原料法合成了一系列ZSM-5/SAPO-5(核/壳)双结构分子筛, 研究了预负载磷酸的条件对核壳结构分子筛的形成及性质的影响, 采用X射线衍射、扫描电子显微镜、X射线能量散射谱和红外光谱等手段对样品进行了表征. 结果表明, 负载原料的预处理条件明显影响磷与ZSM-5间的作用力及复合分子筛的结晶度和颗粒形貌等特性. 与常规合成方法相比, 在适宜的条件下采用这种方法更有利于小颗粒SAPO-5分子筛的形成及其在ZSM-5表面的生长.     

生物蛋清蛋白模板合成海绵状大孔无机氧化物

多孔无机材料因可在微加工,催化,生物分离,电子器件的矿化和色谱载体等方面的广泛应用而引起人们极大的兴趣^[1-9],模板技术是制备孔材料最有效的工具之一,以表面活性剂和嵌段共聚物作为模板剂可以合成出结构多样,孔径均一,有序度高的介孔分子筛（2－50nm),大孔无机材料（＞50nm)通常采用以高分子微球和微乳液作模板的方法来合成（^[10],最近,我们利用浓度极高的;盐溶液和聚苯乙烯球作为模板,合成了3D海绵状大孔和介孔复合的氧化硅薄片^[11][,利用电化学等方法合成了具有特殊光阻性质的大孔氧化硅,氧化钛,金属以及合金材料等^[12],利用电化学等方法合成了具有特殊光阻性质的大孔氧化硅,氧化钛,金属以及合成材料等^[12],也有人利用相分离的方法制备无序大孔材料,但该方法一般较复杂,成本也比较昂贵,自然界中的大孔材料如海藻,珊瑚（氧化硅）是通过生物蛋白质为模板在基胞核内形成的,但是生物蛋白的模板作用和形成机理目前还不十分清楚。