The Synthesis Of Silver-silica Nanocomposites And Their Applications In Surface-enhanced Raman Spectroscopy

Nanocomposites can be combined with different nanoparticles by integrating all their advantages and forming newly unique structural properties. These hybrids are widely used in the field of biological, chemical and food. Based on the Surface-enhanced Raman Scattering（SERS） enhancement effect of Ag nanoparticles and the good uniformity and stability of silica nanospheres, this paper mainly focused on the study of Ag-SiO₂ nanocomposites. First, we developed a new method to prepare Ag-SiO₂ nanocomposites, and then discussed the different effects on their structure and property. Subsequently, the core-shell Ag-SiO₂ and the supported Ag-SiO₂ nanocomposites were characterized and further applied in analysis, respectively. On the basis of their SERS enhancement effect, it was successfully to complete the analysis of acrylamide and bisphenol. Main research and results are as follows:1. The preparation of core-shell Ag-SiO₂ nanocompositeStober method was first adopted to synthesize different size of silica nanospheres with uniformity and stability, and then we investigated the effects of reductant and stabilizer on the core-shell Ag-SiO₂ nanocomposite. In the process of preparation, silica shell possessed a strong negative charge, and the silver ions and reductant was adsorbed on the surface of the spheres and then reacted in the microenviroment. Thus, there is no need to do any other modification with the silica nanospheres. Based on what has been discussed above, the size of the silica nanometer microspheres was finally chosen as 200 nm. Moreover, PVP was acted as reducing agent and stabilizer at the same time in the synthesis of core-shell Ag-SiO₂ nanocomposite.2. The preparation of loaded Ag-SiO₂ nanocompositeWe explored the preparation of loaded Ag-SiO₂ nanocomposite with good SERS enhancement as well as excellent performance of catalytic oxidation, which is very suitable for the research on the catalytic oxidation process towards molecule. The nanocomposite were hybrided by in situ growth of Ag nanoparticles on the surface of 100 nm silica nanospheres with PVP reducing [Ag（NH3）2]+,resulting with a granular structure of nano islands. Furthermore, we studied their catalytic oxidation and the results revealed that this kind of nanocomposite have the potential to be used as SERS substrates and applied in the catalytic oxidation research in dye.3. Ag-SiO₂ nanocomposites used as SERS substrate in analysisAfter preparing the Ag-SiO₂ nanocomposites, we studied their SERS enhancement effect, respectively. The results exhibited that both of the two nanocomposites showed a strong SERS signals and excellent stability as well as good solubility in water.The core-shell Ag-SiO₂ nanocomposite was further realized the SERS detection for acrylamide through thehydrogen bonding interaction between PVP and acrylamide. The proposed method was simple, sensitive and rapid with a lower limit of detection of 0.1 nmol/L towards acrylamide. Moreover, the loaded Ag-SiO₂ nanocomposite was applied to analyze bisphenol A. The results revealed that nanocomposites can be used to rapidly and sensitively determine non-labeled bisphenol A with a lower limit of detection of 5.0μg/L.