Study On Synthsis, Mechanism And Properties Of Micro-/nano-Materials Tungstate

Due to their novel optical, electronic and magnetic properties, micro- /nano-materials of tungstate have potential applications in many fields, such as photoluminescence, hosts for lanthanide-activated lasers, optical fibers, catalyst, magnetic materials, and antibacterial materials. Therefore, it has attracted much interest to controlled synthesize tungstate nanomaterials with various morphologies, to study the size- or shape-dependent properties, and to find their new applied fields. On the other hand, there are abundant resources of tungsten in our country. It is predominant for us to extend the applications of tungstate nanomaterials in industrial fields. In this thesis, we have successfully synthesized a series of micro- /nano materials of tungstate with uniform size and morphology. The influence on the morphology and structure of the obtained products was studied, such as composition of miceoemusion, reaction time, reaction temperature, or additive. And their related formation mechanism and optical properties were also studied.(1) CaWO4 and SrWO4 nanostructures have been synthesized via a simple microemulsion-mediated route. With careful control of fundamental experimental parameters, including the concentration of reactants, the reaction time and the temperature, products with different morphologies (such as dumbbell, coral, rod and dendrite) have been obtained. The possible formation mechanism of these unique morphologies has been proposed based on surfactant self-assembly under different experimental conditions. The as-synthesized CaWO4 samples with various morphologies exhibit different photoluminescence properties.(2) Three-dimensional (3D) hierarchical Bi2WO6 microspheres were successfully synthesized by a simple inorganic salt-assisted hydrothermal process. Morphology modulation of the obtained products could be easily realized by tuning the concentration of nitrate. It is worthy to note that the obtained hierarchical Bi2WO6 microspheres exhibit powerful visible-light-photocatalytic activity for the degradation of Rhodamine-B (RhB) under 300 W Xe lamp light irradiation. A possible salt-assisted formation mechanism was proposed on the basis of the experimental results. Furthermore, this work might represent a novel synthesis strategy for other photocatalysts with desired photocatalytic activity.