Preparation And Property Study Of Micro-/nano-structured Materials For Semiconductor And Composite Nanomaterial

With the rapid development of science and technology,nanomaterials have drawn much attention and been the hot topic because of their many unusual properties and potential applications. However, semiconductor nanomaterials have potential applications in LBD, non-linear material, light-sensitive materials, and photocatalyst materials, due to their lots of terrific properties deriving from their novel effects such as quantum size, small size, and surface. In the future, the manufacture of semiconductor will go into a nano age. In this thesis, we designed some new reaction routes and selected hydrothermal and solvothermal methods, and successfully synthesized Bi₂S₃、Sb₂Se₃、Bi₂Te₃、Zn₂SnO₄ and CdS_0.5Se_0.5 five very important semiconductor nanomaterials, by adjusting type and amount of reactants, solvent type and concentration, reaction time, temperature and other experiment parameters. Meanwhile, we have achieved the control of size and morphology during the synthesis process and studied their hydrophobic, gas sensing properties and photoconductive properties. Hydrothermal/solvent thermal technique has become a common method of preparation of nanomaterials because of its simple process, low investment and low pollution etc. The primary content of this paper is as following:1. Novel Bi₂S₃ hierarchical nanostructures self-assembled by nanorods are successfully synthesized in mild benzyl alcohol system under hydrothermal conditions. The hierarchical nanostructures exhibit a flower-like shape. X-ray diffraction （XRD）, X-ray photoelectron spectra （XPS）, scanning electron microscopy （SEM）, transmission electron microscopy （TEM）, high-resolution transmission electron microscopy （HRTEM）, and selected area electron diffraction （SAED） were used to characterize the as-synthesized samples. Meanwhile, the effect of various experimental parameters including the concentration of reagents and reaction time on final product has been investigated. In our experiment, PVP plays an important role for the formation of the hierarchical nanostructures and the possible mechanism was proposed. In addition, Bi₂S₃ film prepared from the flower-like hierarchical nanostructures exhibits good hydrophobic properties, which may bring nontrivial functionalities and may have some promising applications in the future.2. Synthesis of the metal chalcogenide nanostructures by solvothermal methods: we have successfully prepared Sb₂Se₃ nanowires and sawtooth-like shape Bi₂Te₃ nanorods by solvothermal methods. Firstly, Sb₂Se₃ nanowires have been synthesized by using benzyl alcohol as solvent at 160°C. Secondly, ethylene glycol solution was used as reaction medium and we have successfully synthesized monodisperse sawtooth-like shape Bi₂Te₃ nanorods with uniform size in the presence of nitric acid and surfactant PVP （K90）. Thirdly, the reactant concentration, and reaction time and other factors impact on the morphology have been discussed in details and achieved synthesized for wire-like Sb₂Se₃ and sawtooth-like Bi₂Te₃ under the best conditions. Finally, Sb₂Se₃ nanowire exhibits good photoconductives properties, all these results imply that the Sb₂Se₃ nanowire are promising candidates for applications in high-sensitivity and high-speed nanoscale photodetectors, and photoelectronic switches in the future.3. In this work, highly ordered Zn₂SnO₄ 3D flower-like superstructures assembled with nanorods have been synthesized via a facile one-step hydrothermal route under controlled conditions at 180°C. The products were characterized by X-ray diffraction, field emission scanning electron microscopy, transmission electron microscopy, and selected-area electron diffraction. The morphologies of the samples were found to depend strongly on the concentration of EDA and surfactant. A possible mechanism for the formation of self-assembled Zn₂SnO₄ flower-type super structures is proposed. In addition, the performance of Zn₂SnO₄ gas sensing was studied in detail.4. Synthesis of CdS0.05Se0.05 nanospheres by solvothermal methods: CdS_0.5Se_0.5 nanospheres aggregated from nanoparticles has been successfully synthesized via a simple PVP-assisted solvothermal route. XRD, TEM, SEM and XPS were carried out to characterize the composition and morphologies. In addition, to understand the formation mechanism of the CdS_0.5Se_0.5 nanospheres, time-dependent experiments were carried out through a series of experiments.