Single-Particle Investigation of Plexcitons in Bimetallic Nanorods

Coupling between plasmons and excitons results in theemergenceof novel spectroscopic features directed by the interaction energy,e.g., strong coupling results in the formation of new bands, whereasweak coupling leads to the enhancement of spectroscopic signals. Theplasmon-exciton interaction energies are often determined at the ensemblelevel studies in solution by tuning and detuning the plasmonic resonancefrequency. Herein, we present an efficient method for determiningthe dispersion curves and the Rabi splitting energy of chromophore-boundbimetallic core-shell Au-Ag nanorods by recording their single-particlescattering spectra using dark-field scattering spectroscopy/microscopyin two ways: by placing them on a glass slide and a micron-referencetransmission electron microscope grid. The resonance frequency ofthe plasmonic system is varied by changing the thickness of the silvershell and investigating the coupling with the J-aggregatesof 1,1 & PRIME;-diethyl-2,2 & PRIME;-cyanine iodide. The single-particlescattering spectra of bare Au@Ag NRs are conveniently recorded byremoving the bound chromophore using methanol. The ensemble-levelinvestigations provided similar dispersion curves and interactionenergy, further confirming the reliability of the present method.Moreover, the DFM-TEM method presented herein provides a good correlationbetween the experimental scattering spectra and the theoretical scatteringspectra obtained using finite-difference time-domain simulations.