Construction Of Nanostructures Via Top Down And Bottom Up Strategy And Their Properties

In this dissertation, our goal is to explore to construct higher ordered micro-/nanostructures with specific sizes, shapes, and hierarchies by applying either"top-down"way or "bottom up" way. Moreover, based on understanding the morphology and crystal structural characteristics of the final product, the corresponding structure-dependent properties of the as-obtained inorganic hierarchical micro-/nanomaterials were also investigated in our dissertation. The main parts of the results are summarized briefly as follows:1. Based on the self-modeling of the product's crystal and the "top-down" way on the basis of an etching process, we successfully realized the construction of PbSe hierarchical superstructures. The formation process involve(?) the competition between protection of 1,10-phen and etching of OH" induced etching in crystal facet of PbSe. This facile "top-down" way on the basis of an etching process could also be extended to the preparation of other hierarchical superstructures of functional inorganic materials.2. For the first time, the authors developed a new and convenient route to plant high-quality calcium oxalate dehydrate (COD) tetragonal prisms from the C2O42-source of slow decomposition of L-ascorbic acid. Furthermore, the COD crystals which were obtained in the absence of commonly used polymers or surfactants show impressive higher ordered tetragonal prisms. Subsequently, using COD tetragonal prisms as an important in-situ template, we reasonably design a top-down solid-phase strategy to successfully fabricate macroscaled porous CaCO3 tetragonal prisms with different pore sizes. The as-obtained CaCO3 tetragonal prisms with the different pore sizes are overall safe and environment-friendly, and the application of non-toxic nanoarchitectures as support matrix successfully mitigates the common problems for phase change materials of inorganic salts such as phase separation and supercooling-effect, showing the prospective signs for the application of energy-saving field in the future "smart-house" systems.3. The authors successfully developed the combination of the anisotropic growth of the product's crystal and the "bottom-up" route on the basis of self-assembly process to realize the assembly of one dimensional nanostructures into three dimensional hierarchical flowerlike micro-/nanostructures. Novel flowerlike VO2 (B) micro-/nanostructures were synthesized on a large scale by the perfect combination of both the anisotropic growth of crystal and Ostwald ripening mechanism. Electrochemical measurements predict that flowerlike VO2 (B) possesses favorable discharge capacity, and capacity retention, which suggest its potential applications in cathode materials for aqueous lithium-ion batteries.4. Pure single-crystalline metastable tetragonal VO2 (A) and monoclinic VO2 (B) phase nanostructure have been successfully synthesized via one-step hydrothermal method by hydrolysis of VO(acac)2. It is found that the phase composition (ratio of VO2 (A) to VO2 (B)) of the products increases with increasing the reaction temperature. Therefore, VO2 nanostructure with controlled phase compositions can be obtained in high yields. Both structural analysis and the first-principle calculations reveal the formation from VO2 (B) to VO2 (A) shows a crystallographic shear mechanism. X-ray absorption fine structure spectroscopy (XAFS) has been used as the basic analytic tool. For the first time, X-ray absorption spectroscopy (XAS) of the V L edge and O K edge was performed on the different VO2 phase. Here, we gave the electronic structures of two different kind of VO2.