Plasmon-Enhanced Luminescence of Gold Nanoclusters by Using Silver and Gold Metal Nanostructures

Plasmonic materials can be utilized as effective platforms to enhance luminescent signals of luminescent metal nanoclusters (LMNCs). Both surface enhanced fluorescence (SEF) and shell-isolated nanoparticle-enhanced fluorescence (SHINEF) strategies take advantage of the localized and increased external electric field created around the plasmonic metal surface when excited at or near their characteristic plasmonic resonance. In this context, we present an experimental and computational study of different plasmonic composites, (Ag) Ag@SiO₂ and (Au) Au@SiO₂ nanoparticles, which were used to enhance the luminescent signal of Au nanoclusters coated with glutathione (GSH) molecule (Au₂₅GSH NCs). This specific LMNC has recently attracted particular interest due to its luminescent response and characteristic photostability. Our study presents a wide characterization of the optical and morphologic features of the synthetized particles: plasmonic metal nanostructures and Au₂₅GSH NCs through different experimental techniques including UV-Visible, IR, luminescent spectroscopies, along with TEM and AFM microscopies. Additionally, we have carried out computational simulations based on time-dependent density functional theory (TD-DFT) and classical electrodynamics simulation based on Mie Theory to support our experimental findings. In this study, we report up to 3-fold luminescence enhancement of Au₂₅GSH NCs which is mainly attributed to slow dynamic SEF.