Synthesis And Characterization Of Inorganic Nanomaterials In 12-Tungstosilicate Acid System With Keggin Structure

In this dissertation, soluti0n-based routes were developed to realize the chemical synthesis inorganic nanomaterials. Shape and size controlled synthesis of inorganic materials were demonstrated by ray radiation approach, hydrothermal treated method and soft template approach. Utilizing Tungstosilicate acid ion to synthesize nanoparticles was an important method. Tungstosilicate acid could be as photocatalyst, stabilizer, oxidation agent, reducing agent and template. This route provided a new approach to growing noble metals, semiconductors simple substance, core-shell structures and inorganic compounds. Applications, characters, mechanisms of some substrates were been discussed. The main results are summarized as follows:1. A size-controlled synthesis of silver nanoparticles based on the reduction of silver nitrate by UV-irradiated tungstosilicate acid solution was described. The method allowed synthesis of spherical particles with average size tunable by varying molar ratio of silver nitrate to TSA, pH value of reaction solution and reaction temperature. The silver nanorods were formed from spherical nanoparticles by controlling aging time. The formation of the Arg complexed with TSA ions was demonstrated. The experimental results showed that Arg-TSA colloidal particles were a new kind of organic-inorganic templates for the synthesis of organized assemblies of silver nanocomplex, wherein the Arg-TSA complex acted as a UV-switchable reducing agent for silver ion. Synthesis of spherical particles of any diameters between several nanometers and several hundreds of nanometers could gain by varying molar ratio of silver nitrate to TSA, pH value of reaction solution, and reaction temperature. The formation mechanism of spherical particles was also discussed.2. In this study, we described a size-controlled synthesis of selenium nanoparticles based on the reduction of selenious acid by UV-irradiated tungstosilicate acid solution. The characteristic catalytic behavior of the Se nanoparticles was established by studying the decolorization of cango red in the presence of UV light. It had been authenticated from the study that the nanoparticles afforded a complete mineralization process and the rate of dye decolorization variedlinearly with the Se nanoparticles concentration. The size of the Se nanoparticles affected the rate of dye decolorization also. The formation of Se microwire networks by hydrothermal treated method in tungstosilicate acid solution was described. The kinetics of crystallization of Se assembly was studied as a function of reaction time. During the reaction process, single-crystal Se rods could direct the self-aggregation of the amorphous nanoparticles and promoted the crystallization and transformation process of the amorphous nanoparticles derived from a supersaturation precipitation reaction under mild hydrothermal conditions. The obvious rod-direct epitaxial aggregation process of Se was clearly observed besides the traditional Ostwald ripening process.3. The monodisperse Se core-Au shell and Se core-Ag shell nanoparticles using photochemically reduced tungstosilicate Keggin ions had been synthsized. The Se core structures served as both chemical and physical templates for the coating of Au and Ag were also discussed. The method allowed synthesis of core-shell structure with controllable size of core and thick of shell by varying conditions, such as pH value of reaction solution, and reaction temperature.4. PbSO₄ single-crystal micro-polyhedrons were successfully prepared by reaction of UV-irradiated or hydrothermal treated the mixture of PbO₂ with TSA and Na₂SO₄ solutions. The pH of the reaction solution, the kind of surfactants, the concentrations of surfactants had a significant influence on the growth of PbSO₄. The kinetics of crystallization of PbSO₄ assembly was studied as a. function of aging time and reaction time. The possible mechanism was also discussed. We also studied the room temperature photoluminescent properties of as-prepared PbSO₄ polyhedrons.5. Selective synthesis of uniform single crystalline silver molybdate nanowires in large scale can be easily realized by a facile soft template approach. The synthesis is strongly dependent on the pH conditions, temperature, reaction time and the concentration of TSA. The phase transformation was examined in details. Pure Ag₂MoO₄ and Ag₆Mo₁₀O₃₃ can be easily obtained under no TSA and higher concentration of TSA condition, respectively, Ag₆Mo₁₀O₃₃ nanowires with uniform diameter about 50 nm and length up to several hundred micrometers were synthesized in large scale for the first time at room temperature. The results demonstrated that this route could be a potential mild way to selectively synthesize various molybdate nanowires with various phases in large scale.