Surface Plasmon Research Based On Metal Nanoplate–Molecules–Metal Film Sandwich System

Surface plasmon polarizations(SPPs) is the coupling mode of collective charge oscillation and propagating electromagnetic waves on interface of metal and dielectric. The metal nanostructure has been extensively studied since its unique surface plasmon resonance characteristics. Plasmon photonics in metal nanostructures and surface-enhanced Raman scattering established the foundation for surface catalysis, optical detection, etc.This paper is divided into two parts. In the first part, we mainly studied the plasmon driven surface catalysis reaction of Au nanoplate-molecule-film sandwich structure. In the second part, we studied that Au nanoparticle assisted optical information selective acquisition of molecules from metal encapsulated sandwich structure on the basis of our first work. In the paper, we have analyzed and discussed the results theoretically and experimentally by combining surface enhanced Raman scattering and finite difference time domain method.The surface plasmon resonance in metal nanostructures can produce a strong local elelectromagnetic field enhancement, the p-aminothiophenol(PATP) or 4-nitrobenzenethiol(4NBT) molecules adsorbed on metal surface can be coupled and generated a new molecule namely p, p'-dimercaptoazobenzene(DMAB) molecule under the strong electromagnetic field effects, which can be detected by surface enhanced Raman scattering.The surface catalytic reaction of Au nanoplate-molecule-film sandwich structure mainly depends on the polarization direction of laser and independent of the molecular species. This is because that different polarization direction of the laser can lead the energy to confine in different areas and surface catalytic reaction is more prone to occur in the region with high energy.In our first work, the results pointed out that the Raman signals of interlayer molecule could not be detected in the center of Au nanoplate due to the weak electromagnetic enhancement. In order to solve this problem, we studied a simple way to acquire the Raman information of metal encapsulated molecule. Because of the presence of metal nanoparticle, the electric field intensity of Au nanoplate-film gap increased several times over, and Raman intensity was significantly increased and the surface catalytic reaction occurs. In addition, the results show that the molecule signal enhancement effect of nanoparticle for Au nanoplate-molecule-film sandwich structure are closely related to nanoplate thickness and the particle radius, and are independent of particle shapes and molecular species.Since the simple fabrication of Au nanoplate-molecule-film sandwich structure, the hybrid nanostructures can be widely used in surface catalytic reaction, SERS, light detection, sensors, information store etc.