Preparation Of Nano Silver/Nanofiber Compounded SERS Substrate

For its high sensitivity when using as an analytical method, SERS substrates were made by many ways since SERS had been found for more than 30 years. But most of those SERS substrates were monolayer substrates. To improve the space utilization of SERS substrates, we used electrospin technology to prepare multilayer nano silver compounded nanofibers SERS substrate from in situ synthesized nano silver solution.To research the influence of morphology of nano silver and nanofiber on the SERS effect, in the sencond part of the thesis, by using ethonal/water mixing solution as solvent and poly(vinylpyrrolidone) as both reducing agent and protecting agent, nano silver were prepared when silver nitrate/PVP solution were heated in water bath or irradiated by high voltage mercury lamp. The morphology of nano silver can be controlled by adjusting the ethonal/water mixing ratio, and it turns to irregular nanoplates from nanoparticles when the concentration of ethanol in solvent was reduced. After electrospun the reaction solution, the nano silver compounded nanofiber SERS subtrates were made, and the morphologies of nanofibers were also changed from fibers with high aspect ratio to ball-like shape. It's found that the substrate made from high ethanol concentration solution had the higher SERS effect, and its SERS effect is about 20 times higher than that of monolayer SERS substrate.To solve the promble that the nano silver/PVP nanofiber substrate can not be used in testing aqueous solution, because the PVP is water soluble. In the third part of this thesis, a kind of biomacromolecular which had turnable water solubility, silk fibroin, was used as both reducing agent and protecting agent to prepare silver nanopartcles when silver nitrate/silk fibroin aqueous solution was heated in water bath. It's found that the concentration of silver nitrate influenced the size of silver nanoparticles in heating method, the higher concentration the biger diameter. After turning formation of the silk fibroin from random coil/α-helix toβ-sheet by treating with ethanol, the nanofibers, which was directly electrospun from reaction solution, were water prevented and also SERS activated.