Study On SERS Activity Of Coupled Metal Nanoparticles And The Fabrication Of A New SERS Substrate

Surface-enhanced Raman scattering (SERS) is a unique surface optical phenomenon for that Raman signals of the molecules adsorbed on some metal surface can be enhanced by the factor of several millions. Surface-enhanced Raman spectroscopy shows high sensitivity for detecting the molecules adsorbed on the surface of the metals in sub- and monomolecular layers, and presents plentiful surface information of the molecular structure. Therefore, the spectroscopy has been widely used in some scientific and technical fields in recent years, such as chemistry, biology, surface science, qualitative and quantitative analysis, etc. With the development of the research, SERS is gradually become one of the research methods for the rising monomolecular science.The appropriate substrate is the premises to obtain favorable surface enhancement. Metal colloids are widely used as substrates for their low cost, simple preparation and favorable enhancement. On the basis of the fact that colloidal aggregation has significant enhancement to SERS activity, we focused on the study of the SERS effect in mixed silver-gold colloidal system. The result shows that silver colloid aggregations induced by basic fuchsine form some kinds of cluster-cluster aggregate patterns, while the gold colloid aggregations net-like patterns. The interactions between different kind particles induce the morphologies of the mixed colloid different from pure silver or gold colloid, which results in effectively enhancing the Raman scattering activity. In this paper, the intensities of the SERS signal were effectively enhanced by optimizing the aggregation morphologies of the mixed colloidal systems by means of changing the relative ratio of silver and gold in mixed colloids, the mixed order of gold and silver colloids as well as adsorbed molecules.Additionally, a new method for preparing SERS-active substrate was reported. After exposed, developed and fixed, the commercially available holographic plate can be used to generate attractive SERS-active silver surface. The obtained silver film was characterized by UV-vis spectroscopy and scanning electron microscope (SEM) observation. Its Raman scattering activity was studied by using crystal violet (CV) as the probing molecules. The result shows that the sizes of the silver particles on theprepared substrate are uniform and such substrate has the features of excellent reproducibility, long term stability and high SERS activity. Forthermore, we studied the effects of exposal and developing time on the formation of the silver film. The silver film has stable SERS activity after sufficiently exposed and developed. Moreover, the optimized silver film with desired particle density and size can be obtained by manipulating the exposal and developing.