【作者】 朱君；

【导师】 钱雪峰；

【作者基本信息】 上海交通大学 ， 应用化学， 2010， 博士

【摘要】 由于具有特殊形貌、尺寸和层次的微/纳米材料在基础科学研究和实际应用中具有重要的意义,已受到了人们广泛的关注。而由低维纳米材料作为初级结构单元组装的多级结构更是研究的重点。因此,设计和制备具有特殊形貌、尺寸的多级结构微/纳米材料,并研究材料的结构与性质关系是多级结构材料研究的重要课题之一。在众多多级结构微/纳米材料的控制合成策略中,以溶液过程为基础的“软化学”路线具有简单的工艺和丰富的调控性等而备受关注。其中,在液相中的聚集过程被认为是制备多级结构纳米材料的最有效的方法之一。本学位论文在反应体系设计的基础上,以合适的表面活性剂或有机小分子络合剂为辅助介质,通过简单的液相反应合成了多种具有多级结构的过渡金属化合物微/纳米材料。如发展了气泡模板和界面体系协同合成法,制备了一维项链状氢氧化镉中空纳米材料和三维氧化铜中空纳米球;将微乳液合成法应用于有机/无机杂化半导体材料的制备,合成了8-羟基喹啉锌多级微米片;以络合剂辅助合成策略制备了形貌丰富的氢氧化铟多级纳米材料和硫化镉多级纳米材料。具体的研究内容包括:1、以正辛醇/水两相乳液体系为反应介质,以微波辐照为加热方式,采用界面辅助的气泡为模板快速制备了一维项链状中空Cd(OH)2纳米结构和CuO多级中空纳米球。研究表明阴离子表面活性剂SDS可调节气泡和界面的性质,并可有效地控制产物和初级单元形貌。进一步研究发现,所制备的Cd(OH)2可以用于阴离子染料刚果红的吸附与分离,并且一维项链状中空Cd(OH)2纳米结构能提高对染料的吸附效率。另外,可见光催化降解研究表明多级中空CuO纳米球比非多级结构CuO纳米材料对罗丹明B具有更高的光催化降解性能。2、以简单的阳离子表面活性剂CTAB微乳液体系为反应介质,制备了具有自组装结构的二水合8-羟基喹啉锌(ZnQ2·2H2O)的多级结构,如微米片、三明治结构、六边形结构等。这些多级结构主要由于ZnQ2·2H2O分子的分子堆积和ZnQ2·2H2O初级单元的组装而成。通过反应条件的改变,可以实现初级单元形貌和最终产物形貌的控制。表面光电压结果显示ZnQ2·2H2O拥有p型半导体特性,具有良好的电荷—空穴分离能力。光谱研究表明ZnQ2·2H2O的光学性质与其尺寸和形貌密切相关。3、以络合剂辅助合成法控制合成了不同形貌的In(OH)3纳米材料。当以柠檬酸三钠为络合剂时,适当改变反应条件可以得到纳米粒子、单分散的多级纳米球、单分散的多级纳米立方体等结构的In(OH)3材料。通过络合剂种类、络合剂含量等反应条件的调控,可以进一步控制组装单元和最终产物的形貌及组装方式。进一步地以不同形貌的In(OH)3纳米材料为前驱物,通过焙烧等处理,可得到不同形貌的In2O3纳米材料,且所得到的In2O3纳米材料很好地保持了In(OH)3原始形貌。气敏性能研究表明多级结构In2O3的气敏性能优于In2O3纳米粒子的气敏性能,其中多级结构的In2O3纳米立方体对乙醇气体具有最高的选择性和灵敏性。4、以络合剂辅助合成法控制合成了一系列不同晶型和形貌的CdS纳米材料。系统考察了络合剂酸碱性、络合能力、分子结构等特性对产物晶型和形貌影响。通过络合剂的种类、浓度的改变不仅能够控制CdS的晶型(如立方闪锌矿和六方纤锌矿),还可以控制CdS纳米材料的形貌和组装形式(一维纳米棒组装的多级微球结构、纳米粒子组装的纳米片、纳米粒子组装的多级中空纳米球结构)。研究表明络合剂与Cd2+络合能力及CdS的生长速度对CdS晶型有重要影响,而络合剂与Cd2+所形成的络合物分子结构决定了产物的最终形貌,并对不同络合物体系中CdS的形成机理进行了研究。光催化性能研究表明立方闪锌矿结构CdS的光催化效率优于六方纤锌矿结构;一维纳米棒组装的多级结构CdS的光催化效率优于纳米粒子组装的多级中空纳米球结构。更多还原

【Abstract】 The synthesis and self-organization of micro- and nanoscale inorganic materials with special morphology, size, and hierarchy have attracted considerable attention in the past few decades because of their importance in basic scientific research and potential technological applications. Hierarchical micro-/nanostructures, constructed by using various low dimensional nanomaterials as building blocks, may provide an effective strategy for the systematic study of structure-property relationships and improve the physical and chemical properties of the nanoscale materials with simple configurations. Recently, rational control over the morphology, crystalline structure, and size of hierarchical inorganic materials has commanded the attention of many research groups worldwide and efforts have focused on mastering the synthetic routes to afford a host of novel and diverse nano- and microstructured materials. Various synthetic methods have been devoted to the controlled synthesis of hierarchical inorganic materials with specific sizes and morphologies. On the other hand, solution-phase synthetic methods have many advantages, including relatively low reaction temperatures, convenience in handling, inexpensive reaction instruments, and ease in procedural control, making them very promising for the large-scale synthesis of materials. Furthermore, the aggregation-based solution approach is proved to be one of the most effective methods to obtain hierarchical or complex nano-/microstructures. In this thesis, we have successfully synthesized that ultra-long and flexible necklace-like nanostructures of Cd(OH)2 and CuO hierarchical hollow nanostructures through novel double-soft-template mechanism based on the synergistic effect of bubble-template and interface-template in the n-octanol/aqueous liquid system, hierarchically assembled ZnQ2·2H2O microstructures in CTAB microemulsion system, and hierarchical In(OH)3 and CdS architectures with various morphologies through tunable ligand-assisted synthesis.Detailed research contents are summarized as following:1. Ultra-long and flexible necklace-like nanostructures of Cd(OH)2 and CuO hierarchical hollow nanostructures were successfully prepared in the n-octanol/aqueous liquid system through the microwave heating approach, and a novel mechanism based on the synergistic effect of bubble-template and interface-assistance (SEBI) was proposed. Controlled experiments revealed that both bubble and interface play key roles in determining the self-assembly process of Cd(OH)2 and CuO hierarchical nanostructures, and the morphology/size of building blocks and final products could be readily tuned by adjusting reaction parameters. Further experiments evidenced that the hierarchical Cd(OH)2 and CuO nanostructures possessed superior separation performance on negatively charged dye and photocatalytic efficiency on RhB, respectively.2. Assembled ZnQ2·2H2O microstructures, such as microsheet, sandwich-like structure and hexangular microflake, have been successfully prepared in CTAB microemulsion system through the stacking of ZnQ2·2H2O molecules and oriented aggregation of ZnQ2·2H2O original building blocks. Controlled experiments demonstrated that the morphologies of building block and final product could be readily tuned by reaction parameters, and a formation mechanism, involving re-precipitation, growth and oriented aggregation process, has been proposed. The surface photovoltage revealed that the photogenerated charges of ZnQ2·2H2O could be separated distinctly and ZnQ2·2H2O possessed p-type semiconductor characteristics, respectively. Furthermore, UV-vis and PL spectra evidenced the optical properties of ZnQ2·2H2O were sensitive to its microstructure or morphology.3. In(OH)3 nanomaterials with different morphologies or hierarchical structures, such as nanoparticles, monodispersed hierarchical nanocubes and nanospheres, have been successfully synthesized via a ligand-assisted aqueous process. The shape and size of these as-prepared architectures can be tuned effectively by controlling the reaction conditions, such as the molar ratio of ligand/In3+ and different ligands. Furthermore, In2O3 nanoparticles and monodispersed hierarchical nanocubes and nanospheres with well-defined morphologies of the precursors can be also obtained by annealing the corresponding In(OH)3 samples. Gas sensing properties of the as-prepared In2O3 samples demonstrate that hierarchical In2O3 architectures exhibit a superior response to In2O3 nanoparticles, and the hierarchical In2O3 nanocubes have excellent selectivity and sensitivity to ethanol gas. Further more, XPS spectra and N2 adsorption-desorption isotherms achieve a deeper understanding for the effects of final product morphologies on their gas sensing properties.4. Various architectures of CdS were prepared by a ligand-assisted hydrothermal route, and a series of complexing agents were chosen as organic ligands to controlled synthesize CdS architectures, and some CdS nanostructures with hierarchical morphologies, such as hierarchical jointed microspheres assembled by one-dimensional nanoribbons, hierarchical nanoplates assembled by nanoparticles and hierarchical hollow nanospheres assembled by nanoparticles, were obtained. Furthermore, the crystal phase of the products, including hexagonal wurtzite phase and cubic zinc-blende phase, also can be tuned conveniently by adjusting the reaction conditions, including the sort of ligand, the concentration of ligand and reaction temperature. Finally, the photocatalytic activities of as-prepared CdS architectures with different phases and morphologies demonstrate that biodegradation based on one-dimensional building blocks have a better decolorization than those based on building blocks of nanoparticles, and biodegradation based on based on hierarchical nanoplates with cubic zinc-blende phase have a better response than those based on hierarchical nanoplates with hexagonal wurtzite phase.更多还原