【作者】 宋彩霞；

【导师】 胡正水；

【作者基本信息】 青岛科技大学 ， 应用化学， 2010， 博士

【摘要】 不同形状纳米(微米)晶及其复杂结构组装体的控制合成与性质研究是无机合成化学和无机材料化学的研究热点。本文旨在探索利用简单的水热法实现不同形状微纳米晶的可控合成以及多级结构的组装,发展了对无机微纳米材料形态和结构进行控制的新合成路线,并对所合成的无机微纳米晶及其组装体的结构、形态与性能之间的相关性进行了初步探讨。本文的主要内容归纳如下：1.本文简化了含硫前驱物热分解法制备金属硫化物过程中的分离和提纯步骤,利用新生成的N,N二乙基二硫代氨基甲酸盐在母液中直接水热(溶剂热)分解,控制合成了ZnS、PbS、Bi2S3、CdS等一系列金属硫化物微纳米结构。首次利用单源前驱物分解和Ostwald熟化法相结合的路线制备了ZnS空心球。ZnS空心微球的粒径在220-350 nm,粒径和球壳厚度可以通过调节反应温度和反应时间来加以控制,依据化学反应诱导的Ostwald熟化机制分析了ZnS空心微球的形成过程。PL光谱表明其发光性质非常复杂,除了470 nm的主发光峰外,还有一些弱的可见光区的发光。UV-vis光谱表明所制备的ZnS空心球表现一定的“空心效应”。首次利用该路线控制合成出折纸花状的Bi2S3纳米片和多枝Bi2S3纳米带。折纸花结构的Bi2S3是由褶皱的纳米片自组装而成的,HRTEM图像表明单根纳米带是由多层单晶纳米薄片组成。利用循环伏安实验分析了Bi2S3样品的电化学储氢性能,结果表明Bi2S3样品的储氢能力与其纳米结构的形貌和结构有关,折纸花结构Bi2S3纳米片的电化学储氢能力优于Bi2S3多枝纳米带。初步讨论了Bi2S3纳米结构由纳米片到纳米带的转化过程。提出了纳米带的形成经历了杂化胶体粒子的生成、组装和晶体生长三个过程,并根据“折叠-撕裂”机理分析了由纳米片到纳米带的转化过程。同样方法制备了立方、十四面体等不同形状的PbS微晶,考察了不同实验条件对PbS微晶形貌的影响,简单讨论了两种形态PbS微晶的生长机理,发现PVP的添加量、反应时间、前驱体浓度等对PbS微晶的生长都有很大影响。通过控制结构导向剂PVP的浓度,可以有选择的制备PbS十四面体和立方体微晶以及二者之间的不同形状过渡状态的PbS微晶。同样方法用于CdS纳米结构的制备,得到了一系列由CdS纳米粒子或纳米棒构筑成的星形的纳米结构,讨论了CdS纳米结构的形成机理并且考察了不同CdS纳米结构的光学性质。2.本文采用一步水热法,制备了不同结构和形态的矫顽力可控的α-Fe203铁磁材料,考察各种实验条件对α-Fe2O3微纳米晶结构和形态的调控。所制备的α-Fe2O3鸡蛋形、方块状、桃子状、冬瓜状等一系列实心微球和空心结构微球都有好的单分散性、均匀的尺寸和规则的形状。通过此方法也可以制备单分散的Fe3O4微球。通过样品的磁滞回线探讨了不同α-Fe2O3样品的磁性能与其微结构之间关系,样品的矫顽力、饱和磁化强度和剩余磁化强度均与其形态结构有关,如鸡蛋状α-Fe2O3微球的矫顽力室温下达到3800 Oe,方形α-Fe2O3空心微球的矫顽力室温下达到7800 Oe,这是目前文献报道液相法制备的α-Fe2O3矫顽力的最高值。简单讨论了不同形态α-Fe2O3微球的形成过程,经历了中间相Fe8O8(OH)8Cl1.35纳米棒的生成转化以及α-Fe2O3纳米棒的组装和Ostwald熟化等过程,得到不同结构和形态的α-Fe2O3微球。在CTAB体系中得到了α-Fe2O3菱形纳米晶,该体系中α-Fe2O3具有不同的生长方式,其磁性能与球形聚集体也大不相同,矫顽力为920 Oe,剩余磁化强度为0.17emu/g,饱和磁化强度为0.44emu/g。3.本文采用80℃的低温液相反应制备了ZnO六棱柱构成的花状微结构,并在低温水溶液中很方便地在ZnO棱柱表面沉积了纳米金属Ag,得到花状的Ag-ZnO微结构。该结构具有微米尺度的结构,又有负载于微结构表面的Ag纳米粒子。根据室温PL光谱比较了负载Ag对ZnO花状微结构发光性能的影响,以甲基橙的光催化降解为例比较了两种微结构的光催化性能,实验发现,该复合结构能在较低的Ag负载量时大大提高其光催化活性。采用水热法首次在表面活性剂存在下制备了Ag-TiO2空心结构,以大肠杆菌为例考察其抗菌性能。实验结果表明,该空心结构具有很好的抗菌活性。分析了CTAB胶束模板法制备Ag-TiO2空心结构的基本过程。4.采用水热法,通过改变反应温度选择性地制备了普鲁士蓝纳米立方块和球形组装体,水热反应温度是控制普鲁士蓝纳米晶的主要因素。所得纳米立方块和球形组装体的粒径分布窄,分散性好。通过UV-vis光谱、N2吸附-脱附等温线以及循环伏安曲线比较了普鲁士蓝纳米晶形状与性能之间的关系。普鲁士蓝纳米晶修饰碳电极的循环伏安结果表明该电极对H2O2的电还原具有十分明显的催化作用,可用于制备电化学生物传感器。分别讨论了不同形貌的普鲁士蓝纳米粒子的形成机理。更多还原

【Abstract】 In this thesis, novel synthetic methodologies have been developed to prepare inorganic micro (nano) crystals with specific shapes, for that morphology controlled synthesis and the large-scale self-assembly of the nanoscale building blocks into complex structures have been the focus of significant interests in materials chemistry and device fabrications. Morphology controllable synthesis and assembly of several inorganic micro (nano) crystals have been carried out, and their morphology and shape dependent properties have been investigated. The main points are summarized as follows:1. A simple route has been explored to synthesize sulfides micro (nano) structures through directly hydrothermal decomposition of the as-formed diethyldithiocarbamate precursor in its mother solution. A series of microstructures have been obtained, including ZnS hollow spheres, Bi2S3 microstructures, and PbS polyhedra.A facile one-pot synthesis of ZnS hollow spheres has been carried out, for the first time, via a chemical transformation induced inside-out Ostwald ripening process from a single source precursor. The as-obtained ZnS hollow spheres have sizes in the range of 220-350 nm, and the size and shell thickness can be controlled by adjusting the reaction temperature and reaction time, respectively. Photoluminescence spectra show a dominant emission peak at 470 nm accompanied by several weaker peaks. UV-vis measurement reveals that the obtained ZnS hollow spheres exhibit "hollow effect". The formation process of ZnS hollow spheres has been discussed.For the first time, Bi2S3 nanostructures from paper folding flower-like structures to nanobelts/multibranches were obtained through similar procedure. The synthesized Bi2S3 flower-like structures are constructed with folding of self-assembled nanosheets. HRTEM investigation shows that an individual nanobranch is composed of multiple nanosheets with single crystalline nature. Cyclic voltammograms of the Bi2S3 nanostructures are measured to investigate their electrochemical hydrogen storage behaviors. It was found the capacity of electrochemical hydrogen storage is susceptible to the morphology and structure of Bi2S3 nanostructures, and Bi2S3 roses have superior capacity than that of Bi2S3 nanobelts. The morphology evolution from flower-like nanosheets to multibranched nanobelts has been investigated. It may be determined by both the instinct crystal structures of Bi2S3 and the folding-splitting crystal growth mechanism.When extent this procedure to the synthesis of PbS, cubes and truncated octahedra have been obtained selectively. The influence of experimental parameters on the shapes of the PbS micro-crystals have been investigated and it was found that the concentration of PVP and the precursor and the reaction time are key factors for shape controlled synthesis of PbS microcrystals. PbS cubes and truncated octahedral can be selectively obtained by using different amount of PVP. The growth mechanism and the shape evolution progress have been discussed briefly.2. Monodisperse a-Fe2O3 microspheres and hollow spheres of different shapes have been selectively synthesized through the hydrothermal process. The a-Fe2O3 microspheres exhibit egg-like, cube-like, peach-like and white-gourd-like shapes, as well as hollow structures, all of them have good dispersibility, uniform size, and well-defined shapes. Monodisperse Fe3O4 microspheres have also been prepared. The relationship between the magnetic properties and the shapes and structures of theα-Fe2O3 microspheres has been studied. Ferromagnetic investigation shows that the coercivity and the magnetization saturation values of Fe2O3 samples are closely related to their shapes and structures. Egg-like a-Fe2O3 microspheres exhibit high coercivity of 3800 Oe, while cube-like hollow structures show extremely high coercivity of 7800 Oe at room temperature. When CTAB is used as structure directing reagent, a-Fe2O3 rhombohedrons are the main products. The rhombohedron nanocrystals show coercivity of 920 Oe, remanent magnetization of 0.17 emu/g, and saturation magnetization of 0.44 emu/g exhibiting different magnetic properties from a-Fe2O3 microspheres. A hydroxide precursor of Fe8O8(OH)8Cl1.35 have been captured in all the shape evolution process of a-Fe2O3. And the decomposition and assembly of the precursor nanorods toα-Fe2O3 microspheres as well as the Ostwald ripening process are responsible for the shape evolution of Fe2O3 samples.3. Simple solution methods have been explored to synthesize Ag loaded oxides semiconductor hierarchical structures with high photocatalytic activities. Radical-shaped ZnO microprisms were synthesized via a facile low temperature solution route, then, metal silver was facilely deposited on the surface of ZnO to form Ag/ZnO microstructures. The results showed that the deposition of metal Ag nanospecies were achieved successfully by simply aging the solution at 75℃, and the radical-shaped microstructures of ZnO were well maintained. The Ag/ZnO microstructures exhibit much lower PL emission intensity than that of radical-shaped ZnO microprisms, while much higher photocatalytic activity than that of the pure ZnO. Ag-TiO2 composite hollow structures have been obtained via a one-pot surfactant-assisted hydrothermal method. TEM measurement reveals that the sample is composed of hollow spheres and their tube-like aggregates. The surfactant cetyltrimethylammonium bromide plays a key role in the construction of the Ag-TiO2 hollow structures, which involves templating the CTAB micelles. These microstructures are characterized to ascertain their antibacterial activity which was investigated using the disk agar diffusion method, showing potential antibacterial activity against Echerichia Coli bacterium of clinical interest.4. Prussian blue nanocubes and nanoellipsoids have been synthesized selectively with variation of reaction temperature via a hydrothermal process. Both the nanocubes and nanoellipsoids have a narrow size distribution and a good dispersibility. UV-vis spectra showed that the excitonic peaks of the nanocubes and nanoellipsoids are 683 nm and 674 nm, respectively. Cyclic voltammograms of PB nanocubes and nanoellipsoids modified carbon paste electrodes showed two pairs of redox peaks and a dramatic catalysis for the reduction of H2O2. The possible formation mechanism of different shaped Prussian blue nanoparticles has been discussed and their shape related properties are briefly explored.更多还原