Angle-Resolved Fluorescence of a Dye Coupled to a Plasmonic Nanohole Array

Featured Application: Gold nanohole arrays represent a valid platform to realize multiplexed, label-free biosensing devices based on both plasmon-enhanced fluorescence and surface plasmon resonance detection methods. This has to be achieved by properly co-optimizing the gold nanohole array plasmonic response in combination with the fluorophore, or target molecule more in general, features, and also by choosing the optimal measurement configuration for both the sensing methods. Gold nanohole arrays are periodic metasurfaces that are gathering huge interest in biosensing applications. The bi-dimensional grating-like structure defines their plasmonic response, together with the corresponding mode of angular dispersion. These properties can be used to investigate the interaction processes with the fluorescence features of a properly chosen emitting molecule. By employing a custom gold nanohole array alongside a commercial organic dye, we conducted an accurate angle-resolved optical characterization resorting to fluorescence, reflectance, and transmittance spectra. The coupling between the plasmonic modes and the fluorescence features was then identified as a modification of the dye fluorescence signal in terms of both spectral redistribution and enhancement. By carefully analyzing the results, different measurement efficiencies can be identified, depending on the set-up configuration, to be properly engineered for sensitivity maximization in plasmon-enhanced fluorescence-based applications.