Controllable Synthesis And Formation Mechanism Of Micron And Nanoscale Metal Sulphide Via Biomolecule's Assistance

The goal of this dissertation is to explore and study semiconductor metal sulphides micro and nano-scale materials such as PbS, CuS, Ni3S2, NiS, ZnS with special structures and novel morphologies via the assistance of L-methionine, and is to investigate the relationship among their structures, morphologies, sized and capabilities. Based on the experimental results, a possible growth mechanism was proposed to explain the formation of the as-synthesized architectures. And the optical properties of the obtained products were also studied. According to the results, some kinds of rules were drawn to synthesize micro and nano-scale materials which are self-assembled. Taking semiconductor metal sulphides such as PbS, CuS, Ni3S2, NiS, ZnS for example, by adjusting the reaction parameters, such as the molar ratio of the reactants, the volume ratio of the mixed solvents, the reaction temperature, the reaction time, the crystal structure and the morphology of the products can be effectively controlled.The main contents of the dissertation can be summarized as follows:1. PbS fishbone-like architectures were synthesized by using a biomolecule (L-methionine)-assisted approach in a mixture solvent made of ethanolamine (EA) and distilled water. Additionally, other PbS homogeneous morphologies (e.g., hexapod-like, coralloid, dendritic) were obtained through altering the experimental parameters, such as the molar ratio of the reactants, the volume ratio of ethanolamine (EA) and distilled water. Meanwhile, the optical properties of the as-synthesized PbS fishbone-like architectures were characterized by photoluminescence spectrum at room-temperature and a strong blue light peak centered at a wavelength of 423 nm is observed. Simultaneously, according to the experimental results, a possible growth mechanism was proposed to explain the formation of PbS fishbone-like architectures. The present work proves thatâ…£-â…£semiconductor micro-or nanocrystals with controlled phase and morphology can be achieved via solvothermal route by selecting some appropriate biomolecule which acts as not only structure-directing agent but also sulfur source. The above results of research have been published in Journal of Physical Chemistry C.2. A reaction solution made of absolute ethanol and distilled water was developed to synthesize CuS micrometer-sized solid cubes which were composed of close-ordered nanoparticles via a biomolecule (L-methionine)-assisted approach. To our best knowledge, it is for the first time that the morphology of CuS cubes is obtained. Based on the experimental results, the volume ratio of absolute ethanol and distilled water played a key role on the morphology of the products. The optical properties of CuS cubes were investigated by UV-vis absorption and a broad absorption peak centered at a wavelength of 675 nm is observed, and the unusual phenomena may have potential applications in the optical field.3. Nickel sulphides microcrystals and zinc sulphides microcrystals (including wurtzite and zinc blende) with tunable phase and morphology were synthesized by using L-methionine molecule as structure-directing agent and sulfur source in a mixture solvent made of ethanolamine (EA) and distilled water. It was found that the phase and the morphology of nickel sulphides could be controlled by adjusting the Ni/S ratio of the reactants, that the phase and the morphology of zinc sulphides could be controlled by changing the solvent. For instance, with the molar ratio of Zn(Ac)2-2H2O to L-methionine increasing from 1:2 to 1.5:1, Ni3S2 microspheres composed of nanoparticales and NiS microtubes with several edges on the surface and NiS complex microflower-like structures can be successively obtained. By adjusting the volume ratio of ethanolamine (EA) and distilled water, various morphologies of wurtzite ZnS were obtained (microflower-like structure and a chain of semi-spheres). When the mixture solvent was replaced by NH3-H2O and distilled water, microspheres-shaped blende zinc ZnS were obtained. Meanwhile, the optical properties of ZnS with different phase and morphology were investigated by photoluminescence spectrum. According to the experimental results, a possible growth mechanism was proposed to explain the formation of Ni3S2 sphere-like architectures.