Plasmon–Exciton Coupling in Flexible Ag/Fluorescein Hybrid Nanostructures for Enhanced Fluorescence Applications

In this work, the fabrication and optical characterization of flexible hybrid plasmonic-excitonic films were made, which included a PDMS substrate covered by a dispersed Ag layer and a fluorescein/PVP top layer. The coupling of localized surface plasmon modes (SPPs) in the Ag layer with the excitonic transition of fluorescein molecules resulted in a strong enhancement of the fluorescence emission intensity. This effect is largely attributed to the good overlap of the spectral response of the silver plasmon, around 420 nm, with the fluorescein absorption band around 490 nm, providing the necessary conditions for an effective plasmon-exciton interaction. In addition, the laser-induced fluorescence (LIF) spectrum for an excitation wavelength of 532 nm evidenced the presence of a strong emission peak around 530 nm, whose intensity linearly depends on the excitation irradiance, indicating that the stability of the coupling process is guaranteed with in the system Hybrid architectures based on the PDMS/Ag/fluorescein-PVP guarantee brilliant future prospects regarding their implementation in biosensing and nanophotonic systems due to their flexibility, low cost, and scalability.