Fluorescence enhancement assisted by the double plasmonic modes of gold nanorods

Metal nanocrystal has attracted extensive interest due to its nanoscale confinement of electromagnetic field near the metal surface far beyond the diffraction limit. Fluorescence enhancement is one of the promising applications based on the interaction between such confined near field and fluorescence molecules. Here we present an interesting method by utilizing double surface plasmon resonance (SPR) modes of gold nanorod (GNR) to efficiently enhance the fluorescence. With the transversal and longitudinal mode separately matched with the excitation and emission of the fluorescence, a 4-time fluorescence enhancement factor has been achieved for the GNR-assisted nanosystem compared to the nanosystem based on gold nanosphere (GNS). Since the single SPR mode of GNS supports only excitation enhancement of the fluorescence, such double-mode enhancement scheme creates a flexible way for the fluorescence enhancement, which is superior to the traditional single-mode assisted enhancement method.