Controlled Synthesis And Properties Of Multinary Sulfide Nanostructures

The goal of this thesis is to enrich and develop the new controllable syntheticroutes to prepare multinary chalcogenide materials based on solution synthesismethods. In this thesis, ternary and quaternary chalcogenides have been fabricated viavarious routes. The morphology, phase, structure and properties of the products havebeen systematically investigated. The detailed contents including three parts can besummarized as follows:1. A solvothermal technique using spinel In3xS4as the precursor and usingdifferent copper sources and complexing agents have been developed to fabricatezinc-blende CuInS2, wurtzite CuInS2, and spinel CuIn5S8nanocrystals. Experimentsprove that the acidic or basic conditions are critical for the formation of zinc-blendeCuInS2, while the reducibility of DDT is pivotal for wurtzite CuInS2. The decrease ofthe ligand coordination ability due to the formation of the OA OLA complex thenplays a key role in the synthesis of spinel CuIn5S8and results in a larger nanocrystalsize. The UV Vis NIR spectra of the prepared zinc-blende, wurtzite, and spinelCu In S nanocrystals exhibit a broad-band absorption in the entire visible region andshow band gaps of1.55,1.54, and1.51eV, respectively, which would make themparticularly interesting for potential applications in photovoltaic devices.2. The wurtzite CuInS2hollow-sphere films have been successfully prepared oncopper substrate by a self-designed solvothermal detached system, which is a novelsynthesis approach for multinary chalcogenide materials. The films of Cu(OH)2one-dimensional nanostructure arrays and thioacetamide were used as the precursorsand triethylene glycol was used as the solvent. Experiments showed that the amountof indium trichloride played a determinative role in the final morphology of theproducts. Meanwhile, the one-dimensional nanostructure arrays and the detachedsolvothermal system have great influences on the crystal shape as well. Based on theexperimental results, a possible formation mechanism for the CuInS2hollow spheresalso have been proposed. The UV-Vis absorption spectrum shows a broad absorptionover the entire visible light even extending into the near-infrared region and presents the band gap of about1.53eV for the as-prepared wurtzite CuInS2, which indicatesthe potential applications in solar cells.3. The quaternary Ag3Pb2Sb3S8nanorods with a good stoichiometry have beensuccessfully fabricated via a facile solution reflux route. X-ray diffraction patternsshow that the products have the monoclinic diaphorite structure. The X-rayphotoelectron spectroscopy and energy dispersive spectroscopy analyses prove thatthe elemental composition is very close to the stoichiometry of Ag3Pb2Sb3S8phase.The transmission electron microscopy analyses reveal that the product consists ofAg3Pb2Sb3S8single crystalline nanorods with a preferred growth direction along baxis. These rod crystals have a relatively broad size distribution with diameters of100~200nm and lengths of0.5~2m. This preparation method for the artificialmineral nanostructures should be expected to be extendable for the synthesis of othermultinary chalcogenides. Further systematic research on the control of the phase, sizeand shape, and the investigation of the electrical properties of the products, isunderway.