Controllable Synthesis And Characterization Of Nanoscale Semiconductor Metal Selenides And Tellurides

Nanoscale semiconductor metal selenides and tellurides have attracted substantial research interests during the past years. It has been demonstrated that the optical, electrical and magnetic properties of them could be tailored in a controllable way by altering their structure, morphology, dimension, or composition. In this dissertation, valuable researches have been carried out to the exploration of new synthetic methods in solution phase, and controlled syntheses of metal selenides and tellurides. The main point can be summarized as follows:A low-temperature elemental-direct-reaction route to nanocrystalline CdSe and ZnSe, and further more, by using the newly produced Se with high reactivity as reactant, a controllable synthetic route named "selenite reduction hydrothermal method" have been developed. Various chemical strategies have been introduced to the system to affect the dynamics of reaction, and thus, to adjust the nucleation and growth process. By using appropriate complexing agents as controlling reagents and adjusting the reaction temperature, both morphologies (nanorods and fractals) and structural phases (zinc blende or wurtzite structures) of CdSe nanocrystals can be easily controlled.A precipitate slow-release controlled method was designed in the synthesis of manganese selenides. High quality cube-like MnSe2 and sphere-like (-MnSe micro-crystals have been obtained in aqueous solution at low temperatures (100(C~180(C). By using tellurite as reactant, uniform CoTe and NiTe nanocluster wires were successfully synthesized through a co-reduction process. Through the competition of ionization equilibrium of ZnO22- and precipitation reaction, the nucleation and growth process of ZnSe have been adjusted, and monodispersed ZnSe semiconductor hollow microspheres are obtained. These microspheres were found to form through aggregation of small ZnSe nanocrystals sizes of which could be finely tuned by temperature control. A novel gas-liquid interface aggregation mechanism was proposed and this idea might be generalized in other systems. Optical characterization showed interesting photonic properties and attempts to assemble them into 2D and 3D arrays were carried out. The core/shell structures of ZnSe/MSe (M=Ag, Cu, Pb, Cd) microspheres were also synthesized by a simple substitution reaction.