The Spectroscopy Property Study Of Pyridine-Metal Nanoparticle System

Since Fleimann et al have founded the enhanced Raman signal of pyridine molecules on the silver electrode in1974, the study of surface-enhanced Raman scattering (SERS) have made a great progress. It’s emerged as a very powerful and highly sensitive technique for in situ studying of molecules adsorbed on metal surfaces. For its enhancement, the two primary enhancing mechanisms are generally accepted, One is the electromagnetic mechanism, which is due to the increase of the electric field at rough surfaces or regions in the small gaps between nanoparticles or nanostructures used as the substrates. The other is chemical enhancement which may favor strong resonant Raman scattering via charge transfer (CT) between the metal and the molecule. Pyridine is a good candidate molecule for SERS theoretical studies, because of its good adsorption properties and structural simplicity which belongs to the C2v symmetry. Especially the system of pyridine adsorbed on silver or gold sol particles of nanosize, where the new band appeared in infrared region attracted people much attention for long time. This band can be associated with chemisorption of molecules on colloidal silver and probably to the charge-transfer transition band between silver particles and adsorbed molecules. It is very important to study surface-enhanced spectroscopy that understanding the relationship of between this new absorption band and the SERS enhancement mechanism. However, the mechanism of this new absorption bands have been no exact theoretical evidence that it is closely related to the charge transfer. So it is very essential to carry out the experimental and theoretical research on the occurrence mechanism of the new adsorption band which caused by the interaction of adsorbed molecule and noble metal nanoparticles. In this dissertation, my research work is reported as following:1. I successfully synthesized gold and silver colloidal nanoparticles, studied the absorption spectrum characteristics of them and time resolved absorption and Raman spectrum property after drop pyridine.2. Analyzed and propose contradiction which the new absorption band should belong to, and further illustrated this contradiction through SERS spectra, presented the importance of the adscription of the absorption band.3. Through theoretically simulate the process of molecular adsorption onto the metal nanoparticles, confirmed the mechanism of a new absorption band appearance, so that the experimental results with theoretical calculations have been mutually confirmed.4. As this While, I successfully fabricated a micro-nano array structure of silver by using polystyrene microspheres as template, and studied the property of the surface plasmon of silver micro-nano arrays structure.