Optical Research And Preparation Of SiO₂Nanospheres And Ag/SiO₂Composites

Silica nanoparticles and its composites have distinctive properties, such as high tenacity, high temperature resistance, corrosion resistance, infrared absorption, etc. Owing to their meritorious properties, silica and its composites have a wide range of application, for example, catalyst, drug delivery carrier, antibacterial agent and biochemical detection, and so on. On account of these characteristics, silver/silica composites has become a research highlights in the field of material science. Therefore, how to prepare Ag/SiO2nanocomposites with controllable size, morphology and structure using a simple and economical method tends to be an urgent problem.Currently, different approaches have been proposed to form Ag/SiO2composites. These include electroless plating, layer-by-layer deposition process, thermal decomposition method and sonochemical deposition, etc. Some of these methods have relatively high requirements on equipment and operator. Or the operations are cockamamie. These limits the batch production, industrial application and scientific research of Ag/SiO2. In this paper, we improved the sol-gel method aiming at the shortcomings of the existing technology. First, we summarized the influence law of the temperature and PH on the morphology and size of SiO2and Ag/SiO2composites by varying the experimental parameters. Then, Ag/SiO2and SiO2-N-Ag composites were prepared using the silica nanoparticles, combining with the current research hotspot about the catalytic and antibacterial properties of silver nanoparticles. The light absorption performance of the composites were studied. This work has an important guiding role for the preparation of photocatalyst and antibacterial materials. The detailed contents are as follows:(1)Through the improved stober method, using tetraethoxysilane (TEOS) as silicon source, ammonia as catalyst, we obtained the silica spheres with controllable particle size in alcohol aqueous solution by changing the experimental parameters. The surface of the silica is abundant with hydroxyl, which is conductive to further modification and actual production application. Furthermore, we made a analysis on the formation mechanism of mesoporous silica, which provides theoretical basis for its application in adsorption, catalysis, and drug delivery.(2) We prepared the Ag/SiO2composites by sol-gel method, using sodium citrate as reducing agent and discussed its visible light absorption performance. The results show that the structure of this kind of composites is stable and the Ag nanoparticles on the surface of SiO2is not easy to be oxidation, which can maintain the activity and physicochemical properties for a long time. The thickness and roughness of the Ag particles are affected by the solution temperature and the PH value. The optical performance of the sample can be adjusted by changing the thickness of the silver and the size of the silica. When the PH is9,10,11, the Ag/SiO2composites shows good visible light activity. Among them, the optimization condition is PH=9, T=85℃.(3) The structure, morphology and properties of SiO2-N-Ag composites were researched. The silica spheres were modified by APTES before the synthesis of SiO2-N-Ag composites. From the FESEM figures, the reduction of a small amount of Ag+by NaBH4is the key step to generating nucleus of metallic silver. This step is crucial to the dispersibility of Ag particles on the surface of silica spheres and the optical property of the SiO2-N-Ag composites. Though the EDS did not detect the presence of N elements, the-NH2stretching vibration peak can be found in the FTIR spectrum, which indicates the-NH2were connected to the surface of SiO2successfully. The UV-vis analysis shows that the content and dispersibility of Ag particles are the key factors which affect the optical performance of SiO2-N-Ag composites.The method of preparation of SiO2and Ag/SiO2involved in this paper is completely feasible. This work plays an important guiding role in the preparation of catalyst and antibacterial materials. This method can be used for preparation of the materials that used for biochemistry detection by optimization and improvement.