Raman peak enhancement and shift of few-layer graphene induced by plasmonic coupling with silver nanoparticles

Few-layer graphene was transferred directly on top of Ag nanoparticles, and the coupling between graphene and localized surface plasmons (LSPs) of Ag nanoparticles was investigated. We found that the surface enhanced Raman spectroscopy of graphene was increased approximately 7-fold by near-fields of plasmonic Ag nanoparticles and the enhancement factor of graphene G peak increased with the particle size. Meanwhile, the LSP resonances of Ag nanoparticles exhibit a 10 nm redshift and a 13 nm broadening by the presence of graphene, which can be attributed to the coupling between the Ag LSPs and the graphene.