Surface Enhanced Raman Scattering from Silver Nanoparticle Arrays on Silver Mirror Films: Plasmon-Induced Electronic Coupling as the Enhancement Mechanism

Analysis of surface enhanced Raman scattering spectra from 20 different molecules adsorbed on substrates composed of silver nanoparticles immobilized on silver mirror films revealed competitive Raman enhancement from different types of molecules simultaneously present on the surface. The observed SERS behavior could not be explained using local field enhancement or charge-transfer models. A different SERS mechanism is proposed based on plasmon-induced electronic coupling between the oscillating electrons in the metal and the electronic system of adsorbed molecules. It is suggested that this mechanism has general applicability to other SERS-exhibiting systems.