Fluorescence Enhancement Dependence on Refractive Index Variation in a Nanostructured Plasmonic Surface

Nanostructured plasmonic surfaces have been the subject of many biosensing applications exploiting surface-enhanced fluorescence in the last few years. For this reason, we investigated the refractive index dependence of the coupling mechanism between the plasmonic modes and the fluorescence processes. The results show that the fluorescence emission spectral shape is controlled by the plasmonic field distribution, together with the enhancement of its signal. By altering the refractive index at the plasmonic active surface, the resonance conditions of the plasmonic modes change, resulting in a reshaping of fluorescence emission and a different spectral distribution of the largest enhancement regions.