Plasmon-Induced Suppression of Exciton Self-Trapping in Polymer-Bound Pseudoisocyanine J‑Aggregates

Features of plasmon-enhanced fluorescence in pseudoisocyanine (PIC) J-aggregates formed in polyelectrolyte films at liquid nitrogen temperature have been studied. Due to efficient exciton self-trapping in polymer-bound PIC J-aggregates, their fluorescence spectra consist of two well-separated bands: a narrow near-resonant band belonging to free excitons and a wide red-shifted band assigned to self-trapped excitons. It has been found that in hybrid complexes composed of polymer-bound J-aggregates and gold nanoparticles placed on some optimal distance from J-aggregates, the interaction with plasmon resonance of gold nanoparticles leads to an increase in free-exciton fluorescence, whereas self-trapped exciton emission slightly decreases. Suppression of exciton self-trapping due to plasmon-induced enhancement of the exciton coherence length has been supposed and confirmed by a 2-fold decrease in the exciton–phonon coupling constant.