Synthesis And Characterization Of Metal Sulfides Nanomaterials From Single-source Molecular Precursors

The present thesis explored a new class of methods to synthesize the semiconducting nanoparticle of binary or ternary metal sulfides. Using the self-prepared single-source molecular precursors, the phase, shape and size-controlled synthesis of metal sulfides nanomaterials can be achieved by subsequent solvothermal treatment or just thermolysis in air under suitable conditions. And the corresponding formation mechanisms of the products were also discussed. Many modern analysis techniques, such as X–ray powder diffraction (XRD), X–ray photoelectron spectroscopy (XPS), Raman spectroscopy (Raman), Fourier transform infrared spectroscopy (FTIR), transmission electron microscope (TEM), scanning electron microscope (SEM), UV–vis absorption and photoluminescence (PL) spectra, were used to characterize the as–obtained products. The main works achieved are summed up as following:1. The controllable synthesis of hexagonal Zn-doped CdS(Cd1-xZnxS, x=0–0.3) nanorods from a class of solid air-stable single-source molecular precursors (cadmium zinc bis(N,N-diethyldithiocarbamate), Cd1-xZnx-(DDTC)2) has been achieved by two simple steps: first, Cd1-xZnx-(DDTC)2(x=0–0.3) were prepared directly through the precipitation reaction of stoichiometric cadmium sulfate, zinc acetate, and sodium diethyldithiocarbamate in distilled water under the ambient condition; second, pure hexagonal phase Cd1-xZnxS(x=0–0.3) nanorods with different aspect ratios were produced via solvothermal treatment of the precursor compounds in ethylenediamine or 50 vol % ethylenediamine aqueous solution at 180 oC for 12 h. It was observed that the concentration of solvent and the value of x played important roles in the shape, size and optical properties of the products. The possible formation mechanisms were also discussed. The as-obtained products were characterized by XRD, TEM, Raman, FTIR, UV–vis absorption and photoluminescence spectra.2. The controllable synthesis of hexagonal phase Cd1-xZnxS(x=0–1) nanostructures from a class of solid air-stable single-source molecular precursors (cadmium zinc bis(N,N-diethyldithiocarbamate), Cd1-xZnx-(DDTC)2) has been achieved by two simple steps: first, Cd1-xZnx-(DDTC)2(x=0–1) were prepared directly through the precipitation reactions of stoichiometric cadmium sulfate, zinc acetate, and sodium diethyldithiocarbamate in distilled water under the ambient condition; second, pure hexagonal phase Cd1-xZnxS(x=0–1) nanorods with different aspect ratios were produced via solvothermal treatment of the Cd1-xZnx-(DDTC)2 in 80 vol.% hydrate hydrazine aqueous solution at 180 oC for 12 h, while hexagonal phase Cd1-xZnxS nanoparticles were prepared just by thermolysis of the single-source molecular precursors in air at 300 oC for 3 h. It was observed that the value of x affected the shape, size and optical properties of the products. The possible formation mechanism was also discussed. The as-obtained products were characterized by XRD, TEM, Raman and UV–vis absorption spectra.3. The shape-controlled synthesis ofα-MnS and Ag2S microcrystallites from a class of air-stable single-source molecular precursors under mild conditions had been achieved by two simple steps: firstly, Mn-(DDTC)x and Ag-DDTC were prepared directly through the precipitation reaction of manganese acetate or silver nitrate and sodium diethyldithiocarbamate in distilled water under the ambient condition; secondly, pure cubic phasesα-MnS microcrystallites could be obtained via solvothermal decomposition of the Mn-(DDTC)x in 80 vol.% hydrazine hydrate aqueous solution at 90–120 oC for 24 h; and pure monoclinic phase Ag2S could be obtained by solvothermal decomposition of the Ag-DDTC in 80 vol.% hydrate hydrazine at 150–180 oC for 6–24 h. The as-obtained microcrystallites were characterized by XRD, SEM, XPS and UV–vis absorption spectra.4. The in-air synthesis of Ag2S, PbS, NiS and Bi2S3 microcrystallites from a class of air-stable single-source molecular precursors under mild conditions had been achieved by two simple steps: firstly, Ag-DDTC, Pb-DDTC, Ni-(DDTC)2 and Bi-(DDTC)x were prepared directly through the precipitation reactions of the corresponding metal salts and sodium diethyldithiocarbamate in distilled water under the ambient condition; secondly, monoclinic phase Ag2S, cubic phase PbS, a mixture of hexagonal and Rhombohedral phases of NiS and orthorhombic phase Bi2S3 could be obtained by direct thermolysis of the corresponding single-source molecular precursors in air at 200–300 oC for 3 h. The as-obtained microcrystallites were characterized preminarily by XRD, TEM and SEM.The above synthesis routes proposed by us are simple, mild, cheap, high yields and purity; and also important, they are capable of preparing the target products with different morphologies and sizes in a controllable manner, which provides us a good chance for study of the relationship between the structure and property of the nanomaterials with different morphologies and sizes.