Download Design, Synthesis and Characterization of Novel Semiconducting Metal Chalcogenides with Multifunctional Properties Book in PDF, Epub and Kindle
Metal chalcogenides possess a wide range of interesting chemical and physical properties, including low-temperature superconductivity, semiconductivity, ionic conductivity, intercalation, and optical properties. To expand chalcogenides beyond their traditional applications, it is desirable to generate novel chalcogenide materials with multifunctionality for uses in the areas of catalysis, separation, ion exchange, and gas storage by modifying the framework architectures and tuning the chemical components. The primary focus of my Ph. D. study is to design and synthesize chalcogenide materials with new structures and interesting multifunctional properties. The large variety of chemical compositions and structures make it possible to tune the properties, such as band gap, luminescence, pore size, surface area, and thermal stability. Most of the synthesis has been carried out using solvothermal reactions refs in pyrex tube or teflon lined autoclaves. Novel three-dimensional (3D) microporous chalcogenides constructed on building units [M-Sn-Q]n- (M=Zn, Cd, Mn; Q=S, Se) have been obtained. Their structures have been characterized by both single crystal and powder X-ray diffraction methods. Optical diffuse reflectance experiments have indicated that these compounds are semiconductors with intermediate band gaps between 1.5~2.9eV. The successful doping/substitution of 5%~20% Mn and Se in the [Zn-Sn-S]n- structure allows systematic tuning of the band gap and optical properties of this semiconductor compound. All compounds show a high thermal stability over 400°C. Our studies also show that the guest molecules and cations residing in the open frameworks are exchangeable. Another novel two dimentional ion sulfide [Fe(en)3]·[Fe16S20]·en compound was synthesized as well. UV-Vis reflectance spectroscopy showed a very low absorption coefficient and small band gap ~0.5eV. Doping/substitution experiments with Co and Mn replacing Fe were carried out and the properties will be discussed. In summary, this work has provided examples of rational synthesis and property tuning of new functional materials with new structure types, and demonstrated structure-property correlation in metal chalcogenide based compounds. It has provided useful information for the future developments of material synthesis with desired multifunctionality.
