Controllable Preparation And Properties Of Chalcogenide Semiconductor Nanomaterials Research

Nanomaterials of metal chaloegenide like In2S3and PbS, etc. are important candidates for next generation photovoltaic devices, light emission devices, light detectors, photocatalyst as well as biosensors. Therefore, it’s of great meaning, either from the fundamental aspect or from the aspect of further developing their real application, to find effective methods for preparing such nanomaterials and also to unravel their formation mechanisms. On the other hand, with the wider acceptance of concept of "Green Chemistry" and "Environment-friendly Synthesis", it has been a challenging project for researchers to develop new facile, fast, cost-effective, and scalable green ways to prepare the needed high-quality nanomaterials. In this thesis, we ultilize hydrothermal and electrochemical deposition methods, which are regarded as simple but effective ways to synthesize nanomaterials, to prepare nanostructured In2S3thin films and PbS nanocrystals, respectively, and try to find out their formatiom mechanism as well as potential applications.In Chapter one, we first gave a general introduction of the basic properties of nanomaterials and also the commonly used synthesis methods for nanomaterials. Then, we introduced the potential applications of metal chaloegenide in different areas. We especially summarized the recent development on the synthesis of In2S3and PbS nanomaterials since these two materials were mainly involved in this thesis.In Chapter two, we discussed the synthesis and formation mechanism of In2S3porous films composing of interconnected ultrathin curved nanoflakes on ITO by a simple and environment-friendly biomolecule-assisted hydrothermal process, using In(NO3)3and glutathione (GSH) as the precursors while using urea as the pH conditioner. The morphology and composition of this porous film were detailed characterized by different measurements.We also found that concentrations of the pH conditioner and the biomolecule GSH significantly affected the morphology and structure of In2S3films. The as-synthesized In2S3porous films exhibit strong absorption in the ultraviolet region and the early visible region of the UV-Vis spectrum, with the absorption threshold around501nm. As compared with its dense film, In2S3porous film shows enhanced photocatalytic properties for the degradation of Methyl Orange due to its porous and curved nanostructures.In Chapter three, we shape-controlled and synthesized uniform PbS crystals with different morphologies on ITO by a green electrochemical deposition route using PbCl2and sulfur powder as precursors in DMSO-H2O system. Without using any surfactant in our electrochemical deposition process, we obtained rich morphologies of PbS crystals in a bulk amount with uniform size, showing continuous shape change from octahedral to star-like, then to football-like, and finally to cubic morphology, by simple control over the PbCl2precursor concentration. We also discussed such a morphology evolution in detail on the basis of the relative contributions of branching growth and capping effects of the Cl" ions by systematically designed experiments, and gave a possible mechanism for the shape transformation.