Synthesis Of Highly Crystalline Semiconductor Nanomaterials By Hydrothermal Methods

Recently, semiconductor nano-materials have been investigated extensively due to their unique chemical/physical properties. TiO₂ and WO₃, as important semiconductor materials, become the research hotspot. It is well known that titanium dioxide exists in three crystalline polymorphs, namely anatase, rutile, and brookite, and that different type of TiO₂ crystals has different application prospects. Anatase phase exhibits a wide range of application areas such as the photocatalytic decomposition of organic matter, dyes, industrial catalysis, lithium ion secondary battery materials, photosensitive cells in the future, while the rutile phase has many great application prospects in advanced coatings, cosmetics, polymer materials, protection of cultural relics due to its high stability. WO₃, as an important direct band gap semiconductor material, has potential applications prospects in optical information storage, electronic sensor, LED display and single-electron transmission. Therefore, the synthesis of highly crystalline TiO₂, WO₃ has become a hot research topic.In this thesis, the main work carried out and the main results obtained are as following:1: Highly crystalline titanium dioxide nanostructures were prepared from the different concentrations of HCl, H2SO4, HNO₃ solutions as reaction solvents by hydrothermal treatments of the Hex-ncCTAB/TiO₂ Nanoskeleton as a starting material. Nanostructured TiO₂ with different crystalline phase, crystallinity and morphologies were obtained, the morphology, structure, optical properties and catalytic activity of the obtained TiO₂ materials were characterized using TEM, SEM, XRD, SPS techniques. The influence of different reaction time and reaction temperature on crystalline phase and morphology was studied in details.2: TiO₂ crystals with different morphologies were synthesized using the CTAB/TiO₂ composite structure as the precursor, and ethanol, PEG-200, PEG-400, glycerol and their mixed solutions with different proportions of water as reaction solvents. The morphologies and structures of TiO₂ nanocrystals were characterized using TEM, SEM and XRD. The influence of different reaction time and reaction temperature on crystalline phase and morphology was studied in details.3: Highly crystalline of WO₃ crystals with different structures were synthesized using the CTAB/WO₃ composite structure as precursor, and HCl solution of different concentrations as reaction solvents. The morphologies and structures of the WO₃products were characterized by TEM, SEM and XRD. The influence of different reaction time and reaction temperature on crystalline phase and morphology was studied in details.