Enhanced Nonlinear Radiations in Plexcitonic Hybrids of Cyanine Dyes and Silver Nanostructured Films for Advanced Photonic Applications

A quasi-particle named plexciton emerges from the hybridization between plasmons and molecular excitons which exhibits characteristic spectral features, such as Fano resonance and Rabi splitting in extinction, scattering, and reflection spectroscopy. However, the understanding of the fluorescence properties in plexcitonic hybrids remains unclear, especially for nonlinear upconverted emissions. In this Letter, we prepared three-component plexcitonic hybrids with two cyanine dyes (Cy3 and Cy5) coupled to Ag nanostructured films and investigated their enhanced nonlinear radiation, including two-photon luminescence (TPL), second-harmonic generation (SHG), and surface-enhanced Raman scattering (SERS). The plexcitonic hybrids showed a splitting extinction spectrum with five peaks induced by the hybrid of the monomer and dimer excitons in the two cyanine dyes with surface plasmon resonance of the Ag films. Under the laser excitation at 1260 nm, the (Cy3–Cy5)/Ag hybrid had a 6.3-fold enhancement of TPL and a 5.1-fold enhancement of SHG compared to a two-component hybrid of Cy5/Ag. Our experimental results provide valuable insights for designing and manufacturing multicomponent plexcitonic devices with highly efficient nonlinear radiation. The plexcitonic hybrids, characterized by their featured extinction properties and largely enhanced upconverted emission, have great promise for applications in nonlinear optics, quantum information processing, biomedical sensing, and photochemistry.