Research On The Chemical Synthesis And Properties Of SnO₂ And ZnS Nanostructures

Micro and nanoscale inorganic structures refer to materials that have relevant dimensions on the nanometer and micrometer length scale. These structures have unique physical properties that are distinctly different from their bulk materials. Self-assembled micro and nanoscale structures provide a systematic coverage of all basic principles of self-assembly science and technology including materials synthesis and assembly, characterization, and application, which balance the chemistry aspects of materials with physical principles. The goal of this dissertation is to explore the chemical synthesis and properties of inorganic materials and their nanostructures. SnO₂ porous structures were synthesized through thermal decomposition; SnO₂ hollow nanospheres and three-dimensional (3D) assembly structures were prepared by facile solution-based route; SnO₂ hollow spheres and rod bundles were obtained by crystallization method at room temperature; size-selective ZnS hierarchical structures were successfully fabricated. The gas sensing and catalytic properties of the products were investigated, which provided the experimental evidence to understand the relationship between morphologies and properties. The details are summarized briefly as follows:1. The author developed a thermal decomposition method to fabricate SnO₂ porous structures. During the process, the organic molecule as precursor decomposed and the gas given off resulted in the formation of porous structures. In this approach, no additional templates were needed to obtain porous structures, while templates were generally required in previous researches. It was found that the as-obtained samples with high surface area showed potential catalytic activity toward methanol decomposition. Furthermore, this simple method should be potentially extended to fabricate other metal oxide porous nanostructures.2. (a) The author employed a template-assisted route to synthesize SnO₂ hollow spheres. In the system, terephthalic acid acted as cosurfactant, and surfactant sodium dodecyl benzenesulfonate tend to self-assemble to form microemulsion, which were used as the soft template. Terephthalic acid without the large steric hindrance facilitate the formation of hollow nanospheres. And their gas sensing properties were investigated, (b) The author brought forward a solution-based route to produce SnO₂ 3D structures. In this process, tin foil was introduced to the solution system, and acted both as reactant and substrate to support 3D nanostructures obtained. This method carried out without any template, apparatus, surfactants or additional heterogeneous substrates etc. This easily conducted route may present an enlightenment to synthesize other 3D nanostructures.3. The author developed a solution-phase approach at room temperature for the morphology controllable synthesis of SnO₂ hollow spheres and rod bundles. In this method, we developed crystallization process and further combined the soft templates strategy to synthesize inorganic functional nanomaterials with controllable morphology at room temperature. The aggregations assembled by the surfactant, which acted as soft templates, played an important role in the reaction. The advantages of this method are obvious because of its simplicity, convenience, low temperature, morphology controllable, and capability of producing large quantities of samples. Thus, it has greatly simplified the preparation of SnO₂ structures. Meanwhile, their electrochemical and catalytic properties were investigated.4. The author chose a suitable coordinating agent to realize the shape and size control of hierarchical ZnS assembled structures via a one-step approach. Thioglycolic acid (TGA) was used as the coordinating reagent to form a Zn-thiol complex, which could control the nucleation and growth rate as well as assembly process, leading to the formation of ZnS hierarchical structures with different sizes. The products were well characterized and the possible formation mechanism was also proposed. In addition, their photocatalytic properties were explored.