Study On Synthesis Of Nanomaterials Of Nickel Sulfide And Bismuth Sulfide

The dissertation focus on exploring new synthetic methods for nanoscaled semiconducting materials including Bi₂S₃ and NiS₂, on characterzing microstructures and on studying optical properties. Bi₂S₃ and NiS₂ nanotubes were successfully fabricated with controlled morphologies by porous anodic aluminum oxide (AAO) template method. Bi₂S₃ nanoflowers were fabricated via the thermolysis of the single-source precursors and refluxing in the presence of surfactant. Microstructure, growth mechanism and optical properties of all the synthesized nanostructures were studied and discussed.Firstly, porous anodic aluminum oxide (AAO) template was fabricated by two-step anodization. Bi₂S₃ and NiS₂ nanotubes were prepared via a directional infiltration self-assembly route within the nano-holes of the highly ordered AAO template. X-ray powder diffraction (XRD), energy dispersive spectroscopy (EDS), scanning electron microscope (SEM), transmission electron microscope (TEM) and selected area electron diffraction (SAED) were utilized to characterize the structure, compositions and morphology of the samples. The results indicate that the Bi₂S₃ and NiS₂ nanotubes with diameters of 40⁵0 nm and lenghs of 8¹3μm are obtained. The as prepared NiS₂ nanotubes with single crystal structure are cubic phase and Bi₂S₃ nanotubes with polycrystalline structure are orthorhombic phase.Secondly, using Bi(NO₃)₃·5H₂O and C₁₂H₂₅SH as starting materials and NaOOC(CH₂)₆CH₃ as a phase transfer catalyst, Bi₂S₃ nanorods were successfully synthesized by the thermolysis of the single-source precursors bismuth alkylthiolate at 230℃and 250℃. The products were characterized by XRD, TEM, EDS, SAED, SEM, and UV-Vis. The results show that the prepared bismuth sulfide nanorods, with diameters in the range of 50¹10 nm and lengths up of 0.4⁵μm, are orthorhombic phase and single crystal structure. Compared with the nanorods prepared at 230℃, the nanorods prepared at 250℃have higher aspect ratio, larger lengths and almost same diameters. The band gap energy of Bi₂S₃ nanorods are shifted to higher energy of 2.70 and 2.85 eV compared to the typical direct band gap of 1.3 eV of the bulk Bi₂S₃, which exhibits strong quantum size effects. Otherwise, novel flowerlike nanostructures consisting of Bi₂S₃ nanopetals were successfully synthesized by the refluxing with Bi(NO₃)₃·5H₂O and (NH₂)₂CS as reactants and water as solvent in the presence of surfactant including PEG400,OP-10,TX-10,and Triton X-100. Analysis of TEM, SEM, XRD, UV-Vis and SAED shows that the bismuth sulfide nanoflowers are orthorhombic phase and the parameter of crystal cell is a = 0.382 4 nm, b = 1.232 8 nm, c = 1.118 5 nm. The nanoflower is formed by self-assembly of tens of Bi₂S₃ nanopetals with diameters of 50¹50 nm and lengths of 500¹200 nm. It was found that the surfactants plays a key role in determining the morphology of bismuth sulfide nanostuctures.