Amplification of Surface Plasmon Coupled Emission from Graphene-Ag Hybrid Films

Surface plasmon coupled emission (SPCE) is a novel analytical technique in which the isotropic emission of a fluorophore is combined with the surface plasmon resonance of a Ag (or Au) thin film to yield highly directional emission from the so-called plasmaphore and thus greatly increased sensitivity. Here we report a 40-fold amplification of rhodamine B (RhB) fluorophore when graphene is used as the spacer layer in a conventional Ag-based SPCE setup. In addition to protecting the Ag thin film from oxidation, the highly impermeable graphene facilitated pi-pi stacking interactions with the RhB molecules that resulted in an efficient radiated emission from the plasmaphore. In addition, we found that the plasmaphore emission was more sensitively dependent on the in-plane crystallinity (measured by coherence length L-a) of the graphene spacer layer than its thickness. This study describes the unique features of graphene as a spacer layer for SPCE-based analytical platforms and its potential applications in chem-bio sensing and detection.