Wet Chemical Synthesis And Morphology Control Of Sulfide And Oxide Nanomaterials

Nanomaterials and relatived composites have many interesting properties relating size and morphology. Novel electrons, photons and sensors can be designed by their especial structure. Most of the developed synthetic routes to nanomaterials are complicated in process, expensive in cost, this work of the dissertation has explored a series of new wet chemical methods, which present low requirements in equipment and strong adaptability, to synthesize some typical semiconductor nanocrystals with controllable sizes and morphologies under relatively mild and simple conditions by carefully selecting the reaction media, structure-directing agents and processes. Relatived mechanisms were discussed. The main points can be summarized as follows:1. Mn²⁺ doped MS(M=Zn, Cd) nanorods were successfully synthesized through hydrothermal route. With the increase of Mn²⁺ in the samples, the morphology of products become disorder accompanying some nanoparticles. The diameter of nanorods retains almost the same, but the length becomes shorter. Mn²⁺ enters the position of M2+(M=Zn, Cd) by substitution. Both the absorption band edge and the PL emission spectroscopy of MS nanorods shifted gradually to longer wavelength with the increase of Mn²⁺. The results confirm that the doped Mn²⁺ is the major luminescent component and can effectively adjust the optical properties of ZnS nanorods.Indium-tin oxide (ITO) precursor powderswere synthesized by hydrothermal method. The effects of temperature on the preferred orientation morphologies of the precursor powders were studied. Thereby their preferred orientation growth mechanisms were deduced. The effects of temperature on the phase structures and morphologies of the precursors were remarkable. ITO precursors synthesized at 113℃had the most obvious preferred orientation and grew mainly along the [100] direction and exhibited the best morphology of intersecting-rods.2. CuS hollow spheres with a wall thickness about 20 nm and a pore diameter about 150 nm have been successfully prepared using the PSA latex template approach by a layer-by-layer self-assembly technique. Growth mechanism of CuS hollow spheres was discussed.Bi2S3 nanorods has successfully fabricated by sonochemical aqueous solution using PEG as structure-directing agent. The Bi2S3 nuclei show an obvious tendency to arrange themselves in rod-like arrays over extended length scales under soft template. The growth mode of particle?to?particle by self-assembly under soft template is proposed. The band gap energy of Bi₂S₃ nanorods was estimated at about 1.36 eV by UV-Vis absorption spectroscopy.3. Novel twelve-fold symmetrical Cu2-xS single crystals were synthesized by En/H2O solvothermal process,, and they were built up by two layers of about 80–100 nm in thickness. The possible growth process had been discussed. In(OH)3 with cotton-like, bur-like and pod-like morphologies were synthesized at different temperatures by diglycol-mediated solvothermal processes. The effect of temperature on morphology was discussed and growth mechanism was proposed.4. CeO2 nanocrystals with different morphologies were synthesized by adjusting the pH value of the starting solution in water-in-oil microemulsion. Results show that the morphologies of CeO₂ were transformed from granular, to spherical, and to rod-like with the pH of the starting solution varying from 5, to 8, and to11. All samples were indexed to the phase of CeO₂ and Ce(OH)₄, and the molar ratio of CeO₂ to Ce(OH)₄ could be deduced about 0.25. The morphologies of CeO₂ nanocrystals had a little influence on the specific surface area, UV-Vis spectra and PL spectra. The band gap energies of different morphological samples were estimated by UV-Vis spectroscopic method.5. ZnO nanorods modified by PVP were obtained by hydrothermal technique. Comparison of the amount of ZnO nanorods synthesized in the presence or absence of PVP reveals that PVP plays an important role in the preparation ZnO nanorods, but doesn't alter the crystalline structure of ZnO. The optical property of the ZnO nanomaterials could be modified by PVP. ZnO nanorods increase in absorption at UV region, and don't influence the UV-shielding ability and transparency in the visible light region of ZnO. A weak UV emission at 353 nm of PL spectra exhibits the surface of ZnO is passivated and oxygen-related defects were supplied by PVP.