| As one of the important member of the nano family, semiconductor nanomaterials exhibit potential applications in various functional devices in future, due to their unique properties in optics, electronics, and heat. Numerous reports have indicated that the microstructure of semiconductor nanomaterials, such as particle size, particle morphology, special surface and crystal structure, size distribution and particle dispersion etc., affect their optical, electronic, mechanical and catalytic properties largely. Semiconductor nanomaterials with controllable morphology and structure not only have excellent optical, electrical, magnetic and mechanical properties, but also show attractive prospect in the development of new functional semiconductor nanomaterials, such as molecular recognition, elective catalysis, biological sensors, material processing, ultra-high density storage and stealth materials etc. Thus, how to controllable synthesis of semiconductor nanomaterials with various morphologies for exploring their peculiar physical and chemical properties and finding the appropriate applications have become a relentless pursuit of the goal of domestic and foreign researchers.In this dissertation, we reported a new class of liquid-phase synthesis methods to successfully controllable synthesis of semiconductor nanomaterials of ZnO, ZnS and CdS with various morphologies, and improve the properties of ZnS by doping transition metal. By choosing different solvents, adding additives in the reaction solution, changing the solvent ratio and some other experimental conditions, we have precisely controlled the morphology and structure of these semiconductor nanomaterials, and discussed their corresponding growth mechanism. A lots of characterization techniques, including X-ray powder diffraction (XRD), field-emission scanning electron microscopy (FE-SEM), high resolution transmission electron microscopy (HRTEM), near-field scanning optical microscope system (NSOM), micromeritics ASAP2020instrument, surface photovoltaic spectra (SPS) etc. were employed to analyze the composition, structure, morphologies, surface area and optoelectronic properties of the as-prepared products. The detailed contents of this dissertation were summarized as follows:1、A versatile one-step hydrothermal approach for the fabrication of ZnO architectures with controllable morphologies and phase structures was developed by using hydrothermal reaction via ethanolamine assistance. Herein, ethanolamine was introduced as assembling and structure-directing agents to controllable synthesis of ZnO architectures without any other long-chain organic molecules assisted in the one-step hydrothermal process. By adjusting reaction conditions such as the molar ratio between Zn(OAc)2and NaOH and the volume ratio of the ethanolamine/water, the flowerlike, spindlelike, swordlike, and umbellarlike ZnO architectures of hexagonal phase have been obtained. Their morphologies, structures, properties and growth mechanism have been discussed in detail. As a simple, low-cost and short chain organic molecule, ethanolamine plays important roles in the formation and self-assembly of ZnO architectures. The flowerlike ZnO displayed an enhanced photocatalytic performance as compared with the other ZnO architectures under UV-light irradiation in the methylene blue photodegradation experiments at ambient temperature, which may be found application. The facile ethanolamine-assisted hydrothermal route for varied ZnO morphologies could also shed a new light on the preparation of other metal-oxide materials with novel morphologies.2、CdS and ZnS nanostructures with complex urchinlike morphology were synthesized by a facile solvothermal approach in a mixed solvent made of ethylenediamine, ethanolamine and distilled water. The structure, morphologies and optical properties of these nanostructures were characterized by many analysis techniques. The possible formation mechanism for this urchinlike architecture was discussed. The as-synthesized urchinlike architectures were composed of nanorods with hexagonal wurtzite structure. The preferred growth direction of nanorods was found to be the [001] direction, and their size and shape were related to the solution composition. By adjusting the volume ratio of solution, low-dimensional ZnS nanostructures with striplike, rodike, granularike and ZnS microspheres with networklike were obtained. The synergetic effects of ethylenediamine and ethanolamine play an important role in determining the product morphology. The crystal structure and photoluminescence of the products were depended on the solution components. This facile and economical mixed solvothermal approach may hve promise for extension to fabrication of other metal sulfide.3、ZnO nanomaterials with pyramidal structure were synthesized in ternary solution used zinc as reaction substrate and zinc source. By adjusting the volume ratio of solution or selecting different solvent, hexagonal flakelike and rodlike ZnO nanostructure were also obtained. A possible mechanism for the controllable fabrication of this ZnO nanostructure was discussed. Room temperature photoluminescence measurements showed only one UV emission at382nm for ZnO hexagonal flakelike structure, which is the band edge emission emission of ZnO. In addition, a large number of uniforms distributed ZnO nanoneedles with a hexagonal wurtzite structure were synthesized by a SDBS-assisted hydrothermal method. The composition, structure, and morphologies of ZnO nanoneedles were characterized, and the possible formation mechanism was also discussed.4> Transition metals (Mn, Cu, Co) doped ZnS complex nanostructures were successfully synthesized by the mixed solvothermal route made of ethylenediamine, ethanolamine and distilled water. The Mn doped ZnS product was synthesized in the same ternary solutions as undoped ZnS used. The phase and the morphology of the product were characterized by XRD and FE-SEM. The Mn-doped ZnS product exhibits a more regular urchin-like morphology than that of ZnS with crystal structure unchanged. The as-prepared products have good crystallinity with hexagonal wurtzite phase. Further microstructure and composition analysis of the product was performed by the TEM and EDS, which reveals that the product is composed of Mn, Zn, and S, and the ratios of them are in accord with stoichiometric composition of ZnxMn1-xS. No trace of any other secondary phase was observed. The PL spectra of the Mn-doped ZnS urchin-like structures show a strong orange emission at587nm, indicating the successful doping of Mn2+ions into ZnS host. The doped Mn2+ions were the major luminescent component in ZnS nanorods, which have an optimal doping concentration of Mn at3%. The SPV shows that Mn-doped ZnS has a strong photovoltaic response in the range of300～500nm. Subsequently, Cu-doped ZnS dandelion-like structure and Co-doped ZnS flower-like structure were obtained by adjusting the volume ratio of solution. The EDS test and SPVcurves show that the Cu2+or Co2+have doped into ZnS host. |
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