Research On Surface-enhanced Raman Scattering On Several Ordered Substrates And Their Enhanced Effect

The technique of surface-enhanced Raman spectroscopy (SERS) is able to overcome the disadvantages of conventional Raman spectroscopy. It can provide important information of surface molecular structure and kinetic process directly. SERS-active substrates play the key role in SERS research. The ordered SERS substrates obtained much more attention recently, due to their properties of highly enhanced, reproducibility, uniform roughness.The conventional SERS substrates mainly include metal island films, chemical etched metal films, metal colloids and so on. These films have the disadvantages of poor reproducibility and arranged random, which limit the further research of SERS theory and the application of SERS technique. Therefore, it is important to fabricate the ordered surface substrates.In this paper, we fabricated several ordered substrates and obtained highly quality of Raman spectra. Our study is outlined as follows:1.We prepared the two-dimensional Ag nanoparticles (NPs) monolayers by the method of template.We investigated the SERS effect of two Schiff bases on the surfaces.The classical citrate reduction method was employed to prepare the well monodispersed Ag colloids.Based on the principle of templates, the functionalized organosilane was used to modify the glass or quartz. After that, the highly active Ag NPs were distributed on the substrate uniformly. We can use this self-assemble method to obtain highly enhanced, reproducibility, uniform roughed substrate.2.We prepared three size and three shape a-Fe2O3 NPs thin films respectively, and obtained highly quality SERS spectra from 4-Mpy molecules on the films.Based on the principle of templates, hexamethylene diisocyanate (HDI) was used as bridge to link between quartz surface andα-Fe203 NPs. We obtained the highly ordered a-Fe2O3 NPs films. The maximum enhancement factor of 4-Mpy on the films could be reach to 104 compared to that of 4-Mpy in solution. We compared these three size and three shape a-Fe2O3 NPs films respectively, and investigated their effect. These studies revealed the particular features of semiconductor substrates which different from metals, and extended the applicability of Raman spectroscopy. The charge transfer is most likely responsible for the observed enhancement form the surface ofα-Fe2O3 NPs films.3.We prepared a sandwich structure by graphene oxide (GO), Ag piece and Ag NPs.GO was intercalated by 3-mercaptopropyltrimethoxyliane (MPTS).After that, the GO sheets were adducted to Ag piece assembly. At last, colloidal Ag were connected to GO sheets. We investigated this sandwich by Raman spectroscopy, and found that the Raman signal of the large molecular of graphene could be enhanced in this system. This supported the chance to investigate some large molecules.4.We prepared the graphene-metal composites in a water-ethylene glycol mixture system, and used this model to investigate the enhancement mechanism of graphene.metal ions could be easily reduced to form metallic nanoparticles (NPs) after adding metallic salts to the mixture of graphene oxide (GO) in the water-ethylene glycol solution, and the resulting metallic NPs played a pivotal role in catalytic reduction of GO with ethylene glycol. By varying the excitation wavelength of lasers we obtained the SERS excitation profile of G-Au and G-Pd.