Raman Enhancement on Graphene: Adsorbed and Intercalated Molecular Species

Strong Raman scattering is observed from iodine anions adsorbed at ca 3% coverage on single layer graphene In addition, the Raman signal from just one bromine Intercalation layer inside three and four layer, and graphenes is observed We analyze and model Intramolecular electronic, charge-transfer, and multiple electromagnetic mechanisms responsible for this unusual sensitivity Graphene is an excellent Raman substrate for adsorbed species showing intramolecular electronic resonance, because graphene efficiently,, interfering excited state luminescence The Raman sensitivity for adsorbed and intercalated molecular, species is highest for single layer graphene and decreases with increasing These phenomena are compared with,surface enhanced Raman spectroscopy field enhancement and chemical Raman processes in aggregated Ag particles and on flat, reflective metal surfaces The Raman spectra of adsorbed bromine are not observed, despite significant charge transfer to graphene Charge transfer from,adsorbed bromine, Is about one-half of charge transfer from,Intercalated bromine We attribute the large,Raman signal for both evolution with varying graphene thickness is explained by multiple reflection electromagnetic calculations