Synthesis, Characterization And Properties Of Low-Dimensional Bismuth-Related Nanomaterials

Low-dimensional nanostructures have been the focus of extensive studies worldwide due to their unique applications in mesoscopic physics and fabrication of nanoscale devices. Bismuth provides a very attractive model system for studying low-dimensional physical phenomena owing to the light effective masses, long mean free path and high carrier mobility. In this dissertation, the synthesis of bismuth nanotubes and wires and low-dimensional nanosturctures of bismuth-related materials, such as ternary bismuth oxybromide and bismuth sulfide has been explored. A newly rational low-temperature synthetic route has been presented for the synthesis of metallic bismuth nanotubes and a controlled hydrothermal or solvothermal method has been demonstrated for the synthesis of bismuth-related low-dimensional nanostructures. And, magnetoresistance (MR) effect of bismuth, bismuth telluride, and so forth, has been studied. Bismuth nanotubes, a new member of nanotube family, have been prepared through a low-temperature hydrothermal reduction route, whose formation is believed to be associated with the layered structure of bismuth. The structure details of bismuth nanotubes were studied by X-ray powder diffraction, high-resolution transmission electron microscopy and composition analysis. It is observed that bismuth nanotubes melt upon beam irradiation and transform into polycrystalline nanowires.A template-free, solution-phase method has also been demonstrated for the production of single-crystalline Bi nanowires in large-scale by reducing sodium bismuthate with ethylene glycol in the presence of poly (vinyl pyrrolidone). Other than, nanobelts, nanospheres and nanocables of bismuth have been prepared by adjusting reaction parameters.Single-crystalline nanobelts or nanodisks of ternary bismuthe oxybromide have been synthesized by a facile solution-based hydrothermal method using the cationic surfactant cetyltrimethylammonium bromide (CTAB) as the bromine source. The phase and anisotropic growth of crystals are monitored by simply changing the reaction parameters, such as reagents concentration, temperature, pressure and time, on the basis of thermodynamic or kinetic factors. CTAB also plays a unique role in controlling the phases and morphologies of bismuth oxybromide.A comparative study was placed on the methods of hydrothermal or high-temperature vapor phase processes for the synthesis of bismuth chalcogenides nanowires. Single-crystalline nanowires of Bi2S3 and Sb2S3 can be prepared through a high-temperature route by using bismuth oxide and sulfur as the raw materials. And, their bulk prismatic single crystals were synthesized via a novel hydrothermal process, using SbCl3 or BiCl3 and sulfur as the raw materials at 180oC for over 7 days in the presence of diethylammonium chloride (DEACl) or tetraethylammonium chloride (TEACl).The MR of bismuth nanoparticles with different average diameters, bismuth telluride and nanocomposites of bismuth sulfide and bismuth was shown. The quantum confinement and finite-size effects in bismuth have been addressed. The MR effect of these non-magnetic materials is believed to be relevant to the nature of their layered structures and may provide an opportunity for the exploitation of nonvolatile memories and magnetic-field sensors.