Solvothermal Synthesis And Morphology Control Of Titanium Dioxide Nanocrystalline

Titanium dioxide nano-materials have shown a potential value in photocatalysis, photonics, photoelectric conversion, sensors, so it is one of the desired goals to realize precise control of the morphology of semiconductors nanomaterials. In this paper, the research progress of titanium dioxide nanomaterials was summarized and reviewed. Wet chemical synthesis of titanium dioxide nanocrystals had been explored and studied from the experiments. A kind of microemulsion-solvothermal synthesis method of nano-titanium dioxide nanocrystals was proposed on theoretical and experimental grounds. Different shapes of nano-titanium dioxide nanocrystals were also synthesized by controlling the heating rate with two different surfactants. At the same time a preliminary exploration and research ofâ…¡-â…£semiconductor nanocrystal composite technology had also been conducted, which would lay a solid foundation for the control of binary nanocrystalline composite materials.On the basis of traditional high fatty acid synthesis technology for the nano-crystalline preparation, TiO₂ nanocrystals were synthesized at three different conditions including 240℃, 270℃and 300℃for different reaction time under high-temperature solvothermal conditions. The TiO₂ nanocrystals were characterized by transmission electron microscopy (TEM), fourier transform infrared spectroscopy (IR) and X-ray diffraction (XRD) techniques. The shape change and growth pattern of TiO₂ nanocrystals with macro-control condition were further studied. The macro influenced factors to control the morphological changes of nano-structured titanium oxide were found. Control to achieve uniform morphology of nano-titanium dioxide control methods, that is, under the control of low temperature growth rate of nano-crystalline and fully extend the reaction time, lower reaction temperature, and inhibit secondary nucleation, it can tend to be uniform rod-like nano-crystalline titanium dioxide; while controlling the reaction temperature across the low-temperature nucleation zone, to achieve a high temperature or using room temperature control of nucleation, high-temperature limit of-phase growth, and controlling the reaction time, it can tend to get are a bit like titanium dioxide nanocrystal.A new microemulsion-solvothermal method was invented for TiO₂ nano-crystalline synthesis. It had successfully resolved the titania at room temperature controlled nucleation and growth of high-temperature limit of phase problems. The new method had both micro-emulsion technology advantage of better control over the grain size and grain shape and solvothermal characteristics of enthusiasm for a better crystallization. Using tetrabutyl titanate (TBT), oleic acid(OA) and deionized water (H₂O) as the reactant, The homogeneous microemulsion precursor was synthesized at room temperature under stirring. Sphercial TiO₂ nano-crystals with small size distribution were successfully synthesized under solvothermal conditions at 300℃. Several other different shapes including polygon, rhombus and rod were obtained at different temperature and time. Based on an in-depth study of the literature, the formation mechanism and shape change process were systematic and comprehensive studied using fourier transform infrared spectroscopy (IR) and X-ray diffraction (XRD) techniques.Using composite surfactant synthesis, by controlling the heating rate, burn-in time conditions, it had successfully solved the difficulties of the control of the growth rate of titanium dioxide under different temperature. A special solvothermal synthesis method using 1 - dodecanamine (DM) and oleic acid (OA) as the surfactants was proposed for TiO₂ nano-crystalline preparation. Spherical, rod-like, point rods mixed-like, and some irregular-shaped nanocrystals was prepared by controlling the heating rate under solvothermal conditions. On the basis of an in-depth study of the literature, the mechanism of the shape change process under different heating rate was preliminary discussed using X-ray diffraction (XRD) techniques. At the same time, large-size high crystallinity of rhombic titanium oxide nanocrystals was also successfully synthesized with N-N-dimethyl amide (NMF) and oleic acid (OA) which were used as the surfactants. By controlling the precursor processing time, A new kind cube-shaped TiO₂ nanocrystals around 10nm size with narrow size distribution were successfully synthesized in this simple solvothermal way.Using solvothermal synthesis techniques, cadmium nitrate (Cd(NO₃)₂), sodium sulfide (Na₂S) or other sulfur sources such as elemental sulfur, thioacetamide (TAA) as raw materials, CdS nanocrystals were prepared in several different way at different temperatures and reaction time under the effection of different surfactants. The samples prepared were characterized by transmission electron microscopy (TEM). It was found that several different shapes including sphere, rod, triangular cone of CdS nanocrystals with different size distribution were successfully synthesized. We also used solvothermal synthesis process to control the synthesis of rod-like nanocrystals of ZnS. The precursor second hot-injection solvothermal method was used for the preparation CdS, ZnS composite quantum dots. It was a way similar to hot-injection reaction further with a solvothermal process. New microemulsion-solvothermal theoretical model, experimental program and feasibility Analysis for binary core -shell techniques was designed, which would lay a solid foundation for the control of binary nanocrystalline composite materials.