| Due to their novel optical, electronic and magnetic properties, micro- / nano-materials of molybdate have high potential applications in many fields, such as photoluminescence, hosts for lanthanide-activated lasers, optical fibers, humidity sensors, catalyst, magnetic materials, and antibacterial materials. Therefore, it has attracted many researchers'interests that to controlling synthesize molybdate nanomaterials with different morphologies, to research the size- or shape-dependent properties, and to find their new applied fields. On the other hand, there have abundant resource of molybdenum in our country, which is predominant for us to extend the applications of molybdate nanomaterials in industrial fields, and is beneficial to the economic and social value. In this thesis, we have successfully synthesized a series of micro- /nano materials of molybdate with uniform size and morphology. The influence on the morphology and structure of the obtained products was studied by changing the reaction condition, such as: composition of miceoemusion, reaction time, reaction temperature, or heat treatment. And their related formation mechanism and optical properties were also studied. The concrete research contents are summarized as following:(1) Novel hierarchical 3-D architectures of molybdate mesocrystals (such as CaMoO4, SrMoO4, CaWO4, and SrWO4) have been successfully synthesized via a simple microemulsion route by carefully controlling the fundamental experimental parameters, including the temperature, the concentration of aqueous solutions, and the reaction time. The 3-D mesocrystals constructed with nanoparticles show large porosity and surface area. The oriented aggregation mechanism is suggested for the organization of these mesocrystals. Detailed experiment confirms that the mesocrystals are thermodynamically metastable, which can be formed and stabilized under certain conditions. These results of our experiments validate the mechanism of the mesocrystals.(2) We provided a fast method to preparation of 3-D dentritic crystals of BaMoO4 by using microemulsion as reaction medium. The formation mechanism of the dentritic crystals was revealed by investigating the crystal structure, composition of microemulsion,ωvalue, concentration of solution and temperature. Strictly controlled the reaction condition, a novel shape evolution of these dentritic crystals was observed. The 3-D dentritic crystals could evolve to 1-D nanorods and then to 0-D nanoparticles. Minimization of the lattice distortion energy is assumed to drive the metastable dendrites to divide into stable particles. These peculiar shape evolutions of crystals from 3-D to 1-D and 0-D structures have not been reported by previous researchers. Therefore, studies on the shape control and evolution of BaMoO4 crystals will, to some extent, provide insight into crystallization behavior given that the growth history and shape evolution process have traditionally been poorly understood.(3) We prepared a series of metal molybdates macro- /nano-materials via the microemuslion-mediat route. Octahedral CdMoO4 microparticles and some 1-D nanomaterials of transition metal (cobalt, nickel, zinc, copper) were synthesized by microemulsion combined hydrothermal treatment method. Octahedral PbMoO4 nanoparticles with quasi single crystalline structure were obtained by reaction of microemulsion under ultrasonic treatment.(4) Octahedral CdS hollow microcages were synthesized on the basis of the ion interface reaction process by using CdMoO4 crystals as in situ sacrificial templates. The shells of the obtained octahedral CdS microcages were were constructed with nano- building blocks, which could be easily tailored with nanoparticles or nanoplates by different sulfur source. In this study, metal salt was selected as the template in preparing CdS microcages, which may provide a brand-new strategy to synthesize hollow nonspherical structures due to the abundant morphologies of metal salts.
|
PDF Full Text Request