Plasmon-enhanced photoluminescence and SERS in Ag- and Au-based nanohole arrays with Ag nanoparticle decoration

Abstract

We present a comparative investigation of plasmon-enhanced photoluminescence (PL) and surface-enhanced Raman scattering (SERS) in gold and silver nanohole arrays (AuNA and AgNA) integrated within a metal–insulator–metal (MIM) configuration and further decorated with silver nanoparticles (AgNPs). The MIM architecture, composed of an Ag buffer layer, a SiO₂ spacer, and a top Au or Ag nanohole film, supports strong vertical coupling of plasmonic modes confined within the dielectric gap, enabling efficient field localization and exciton–plasmon interaction. The nanostructures were fabricated via colloidal lithography and validated by finite-element simulations. AgNA exhibited stronger near-field confinement, yielding the highest absolute PL enhancement (4.93 × over glass) and pronounced SERS response of rhodamine 6G (R6G). In contrast, AuNA showed weaker absolute signals but achieved a larger relative PL gain (1.96 vs. 1.59 for AgNA) after AgNP growth, attributed to hybridization-induced redshifts improving spectral overlap with the 4-(Dicyanomethylene)-2-t-butyl-6-(1,1,7,7-tetramethyljulolidyl-9-enyl)-4H-pyran (DCJTB) emission. Time-resolved PL measurements revealed shortened fluorophore lifetimes for both arrays, which were further reduced by AgNP decoration, confirming enhanced radiative decay through MIM-assisted plasmon–exciton coupling. These findings elucidate the complementary roles of material damping and MIM hybridization in tuning resonance behavior and provide design insights for plasmonic and optoelectronic applications.