Green plasmonic mode in AgFON structures: A pathway to enhanced SERS sensitivity

In this work, hybrid plasmonic nanostructures based on metal films deposited on ordered arrays of polystyrene nanospheres were designed and characterized, with the aim of pushing the operation to shorter wavelengths and optimizing the ultrasensitive molecular detection through Surface-Enhanced Raman Spectroscopy (SERS). A key finding was the identification of a high-energy green plasmonic mode in AgFON systems with diameters ranging from 700 to 800 nm, a resonance previously unreported in the literature, which extends the resonant excitation range and enhances SERS sensitivity. Additionally, we demonstrated the ability to tune the plasmonic resonances by precisely modulating the geometry of the nanostructures, in both gold and silver film systems. Experimental results, supported by numerical simulations, confirm the potential of these platforms as highly efficient optical sensors for molecular detection applications. The SERS efficiency was evaluated using mercaptobenzoic acid (4-MBA) as a probe molecule, demonstrating the effectiveness of the nanostructures in amplifying Raman signals.