| In recent years, with the development of nanotechnology, the Au nanocatalysts have attracted great attention due to their importance for catalytic applications in a variety of fields. Numerous studies show that dispersed gold nanoparticles on some supporting materials have been used to avoid nanoparticles aggregation, and make the material has better stability of structure and performance. Recently, SiO2 nanospheres are extensively used as a supporting material for Au NPs which are active center because they are inert in character and provide higher active surface area for accommodating metal NPs on their surfaces. In summary, Au-SiO2 composite nanoparticles or core-shell nanoparticles are widely used in industry, due to the dispersed gold nanoparticles on various carriers for catalytic combustion, selective oxidation-reduction reaction, and many different types of reactions have shown extraordinarily catalytic properties. Moreover, the Au-SiO2 composite nanospheres have a potential application in many interdisciplinary the concern has broad application prospects. Therefore, the performance of composite and multifunctional nanostructures (such as magnetic, optical, electrical, catalytic, etc.) will be the focus of future research and application.In this work, we developed an in situ growth method to prepare Au-SiO2 composite nanospheres with good catalytic activity and simple synthetic process for liquid-phase catalysis. The crystal structure, chemical elements, morphology and catalytic property of Au-SiO2 composite nanospheres were analyzed with transmission electron microscopy (TEM), X-Ray powder diffraction (XRD), UV-vis-spectrophotometer (UV-vis), and X-ray photoelectron spectroscopy (XPS). Study its catalytic degradation of organic dyes features. This thesis is divided into about three parts:The first part, monodisperse SiO2 nanospheres were synthesized through an improved Stober method. To study the effects on SiO2 nanometer microspheres particle size through changes the dosage of ammonia and silicon source, respectively. Experiments show that, with the amount of ammonia and silicon source increase, the corresponding size of SiO2 nanoparticles increased. Finally get the desired particle size of SiO2 nanospheres of 130-160nm.The second part, amine functionalized SiO2 nanospheres were prepared with KH-550, then tunable amounts of Au nanoparticles were absorbed on the surface of nanospheres by reduction of tetrachloroauric acid. The advantages of the method include not only simple operation and effective control agglomeration of Au nanoparticles, but also high metal loadings on the surface of SiO2 nanospheres resulting in a high surface area. Analytical results demonstrate that Au nanoparticles (4-9 nm) are homogeneously distributed on the surface of SiO2 nanospheres, which have good FCC crystal structure, and Au species mainly exist in zero-valent metallic state. In addition, these Au-SiO2 composite nanospheres (130-160 nm) can be used as catalyst for the reduction of organic dyes and exhibit a high efficiency in catalysis.The third part, with Rhodamine 6G and Rhodamine B as a probe detects the catalytic activity of Au-SiO2 composite nanocatalysts for organic dyes degradation. Research shows that with the increase of Au loadings nanospheres in Au-SiO2, the catalytic performance was increased and then decreased after the first trend. Au loadings for different catalysts, wherein the catalyst for most of the concentration of the catalytic effect of Rhodamine 6G, Rhodamine B for a few catalytic effect, while increasing the amount of catalyst the catalytic effect is increased accordingly. Au-SiO2 composite nanocatalysts provide a useful reference to further effective degradation of organic dyes on wastewater treatment. Moreover, these Au-SiO2 composite nanospheres exhibit good catalytic properties for the reduction of organic dyes, which may have promising applications in catalysts and wastewater treatment. |
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