Strong coupling effects in a plexciton system of gold nanostars and J-aggregates

Strong exciton–plasmon interaction enables effective control of the photonic properties of hybrid organic–inorganic nanostructures encompassing light absorption, scattering and luminescence. Whereas the manifestations of light-matter interactions in the absorption and scattering are reasonably well understood their relation to the luminescence as well as luminescence properties themselves in strongly coupled plexcitonic hybrids is still largely underexplored especially for a system with a complex mechanism of hybridisation of states. Here we report on investigation of the interaction between localized and hybridized plasmons in gold nanostars and excitons in J-aggregates under ambient conditions. Our findings demonstrate the quality performance of the formed plexciton system with multiple hybridization channels in terms of the parameters of strong coupling, such as Rabi splitting (230 meV), coupling-strength-to-transition energy ratio (0.07), and cooperativity (2.03). The results of time-resolved experiments elucidate the observed enhanced spontaneous emission rate with regard to the Purcell effect, whose value was estimated from the extinction spectra of the strongly coupled plexciton system. [Display omitted] •Hybrid structures of Au nanostars and J-aggregates of organic dye were prepared by self-assembly.•The interaction between plasmons and excitons is studied using optical spectroscopies and luminescence lifetime imaging.•Large values of Rabi splitting, coupling strength and cooperativity indicate achievement of the strong coupling regime.•Enhanced spontaneous emission rate in hybrid nanostructures is observed and analyzed.