Research On Preparation And Properties Of Transitional Metal-VIA Compounds Semiconductor Nanomaterials

With special optical, electrical, thermal and magnetic properties, transitional metal - VIA compounds becomes one of the important research directions of chemistry, material and physics. Based on the investigation of abundant related literatures, we focus our research on the synthesis and properties of transitional metal - VIA compounds. A variety of transitional metal - VIA compounds semiconductor nanomaterials with different morphologies are successfully prepared by various strategies including hydrothermal and solvothermal treatment, evaporation-induced crystallization and so on. The as-prepared products are characterized by X-ray diffraction (XRD), field-emission scanning electron microscopy (FESEM), Transmission electron microscopy (TEM), High-resolution transmission electron microscopy (HRTEM), photoluminescence (PL) and electrochemical analysis. The reaction conditions and mechanisms are investigated. In addition, the optical and sensor properties of some products are also studied. The main points are summarized as follows:(1) Based on previous work, more ordered Cu(OH)₂ nanostructure arrays are synthesized by solution - solid reaction; CuO nanostructure arrays with well aligned nanoplates arrays on the wall of the rods and tubes are synthesized by benzene-thermal treatment of the nanostructured Cu(OH)₂ array precursors.(2) When the reaction for synthesizing Cu(0H)2 arrays is carried out under hydrothermal condition, CuO nanoflowers are obtained.(3) Cubic ZnS hollow nanospheres with diameters of about 100nm have been synthesized by solvothermal reaction of Zn powder and the in-situ prepared S₈ with the mixture of water and ethanol as the solvent. The shell of the hollow nanospheres are assembled by ultra-thin nanoparticals; If the reaction is taken at room temperature and the solvent is only water, cubic ZnS solid nanospheres with diameters of about 400nm is obtained. The surface of the solid spheres is composed of wire-like structures.(4) A two-phase system is designed with (S+CS₂) as oil phase and metal salt aqueous solution as water phase. And a series of micro/nano metal sulfides including CdS, PbS and CuS dendrites, ZnS microspheres, Ag₂S peanut-like nanospheres have been synthesized by the reactions at the oil-water Interface. The experimental results show that this two-phase reaction is a general approach to synthesize various micro/nano metal sulfides.(5) Evaporation-induced crystallization is first applied in the synthesis of transitional metal chalcogenides and a series of transitional metal chalcogenides nanowires have been successfully produced, including Cu₇S₄, Cu_2-xSe, FeS₂ and Ag₂Se nanowires. Among them, CU7S4 nanowires have the length up to hundreds of micrometers and the diameters between 50-100nm. It is found that the evaopration of water plays a crucial role in the formation of the nanowires. The experimental results indicate that evaporation-induced crystallization provides a simple and general method for the synthesis of 1-D transitional metal chalcogenide nanomaterials.(6) According to the principles of sensors, two kinds of sensors including resistance-type sensor and photoluminescence-type sensor are built. It is found that the sensors made from ultra-long CU7S4 nanowires synthesized by evaporation method show high sensitivity to both ammonia gas and humidity at room temperature, with short response/recovery time and good reproducibilities.