Plasmon-Enhanced Resonance Energy Transfer from a Conjugated Polymer to Fluorescent Multilayer Core−Shell Nanoparticles: A Photophysical Study

The influence of metallic silver nanoparticles on Förster resonance energy transfer (FRET) between a water-soluble cationic conjugated polymer and fluorescent multilayer Ag@SiO 2 @SiO 2 +FiTC core−shell nanoparticles was characterized using a combination of light scattering and luminescence techniques. Positioning the fluorescent polymer 7 nm away from the surface of a 45 nm silver nanoparticle with a silica spacing layer increases its quantum yield to 77%, as compared to 3% when measured as an isolated emitter. In the presence of the metallic core, the luminescence of the nanoparticle-bound acceptor fluorophore is increased at the expense of the polymer donor luminescence, and time-resolved fluorescence measurements indicate an enhancement of FRET efficiency from 4 to 50%, an increase in the Förster distance from 50 to 85 Å, and a resonant transfer rate between donors and acceptors more than 2 orders of magnitude higher than that measured in the absence of the metal core. The strong influence of plasmonic coupling in these multilayer nanocomposites offers great potential for signal amplification schemes in polymer-based and FRET-based biosensors.