Preparation And Investigation Of New SERS Substrate

Since the first discovery of surface-enhanced Raman scattering (SERS) on electrochemically roughened Ag electrode in 1974, it has been attracting our great attention for its enormous potential application. Previously Raman Scattering (RS) is limited by its inherent weakness, since only a small amount of light is inelastic scattered. In contrast, SERS is provided with greatly increased signal by orders of magnitude in the presence of nano-structured surfaces. At presnt, we have made great progress in SERS detection of many probe molecules with common substrate ("solid substrates" and "liquid substrates"), but there is still some imperfection, which limits practical use. It becomes urgent to develop a bran-new substrate system to gain stable, comprehensive, efficient, high-sensitive, repeatable SERS signal. The main conclusions are listed as follows.1. Firstly, we looked up abundant articles and made use of these methods. By controlling reaction factor and surfactant added, we synthesized various Au and Ag nanoparticles with different surface property, size and shape. UV-Vis absorption spectrophotometry and transmission eleetron microscopy (TEM) are mainly used to check the stability, size and shape of the colloidal sol.2. We introduced treated Graphene Oxide sheets (GO) with special size as suspended micro-platform to study the loading capacity to different nanoparticles. Then such aggregates/GO multiple substrates could suspend well in liquid phase. Moreover, it's feasible to regulate the size of aggregates and loading density by varying aggregating factor.3. Three kinds of different silver colloidal sol are prepared to aggregate on such platform to obtain substrates. And 4-Mpy was selected as probe molecule to test SERS spectra on these substrates. In SERS spectra, some change in intensity and shift in frequency can be observed compared to normal Raman spectrum due to interaction between molecules and SERS substrates. The representative band at approximate 1600 cm-1(C=C stretching) is selected to calculate the enhancement factor values, and they are around 105.4. We also tested enhancement capacity to Bovine Serum Albumin (BSA) by such substrates. Upon simple mixture of BSA and substrates, apparent SERS signals were immediately obtained. Above all, the mixture could keep stable at 4℃for long, and SERS signals barely changed. It showed the potential of this aggregate system as a convenient and powerful SERS-active substrate for biological detection.