Battling absorptive losses by plasmon–exciton coupling in multimeric nanostructures

Abstract

The strong inherent optical losses present in plasmonic nanostructures significantly limit their technological applications at optical frequencies. Here, we report on the interplay between plasmons and excitons as a potential approach to selectively reduce ohmic losses. Samples were prepared by functionalizing plasmonic core–shell nanostructures with excitonic molecules embedded in silica shells and interlocked by silica spacers to investigate the role played by the plasmon–exciton elements separation. Results obtained for different silica spacer thicknesses are evaluated by comparing dispersions of plasmonic multimers with respect to the corresponding monomers. We have observed fluorophore emission quenching by means of steady-state fluorescence spectroscopy, as well as a significant shortening of the corresponding fluorescence lifetime using TCSPC data. These results are accompanied by the simultaneous enhancement of Rayleigh scattering and transmittance, revealing more effective absorptive loss mitigation for multimeric systems. Moreover, upon decreasing the thickness of the intermediate silica layer between gold cores and the external gain functionalized silica shell, the efficiency of exciton–plasmon resonant energy transfer (EPRET) was significantly enhanced in both multimeric and monomeric samples. Simulation data along with experimental results confirm that the hybridized plasmon fields of multimers lead to more efficient optical loss compensation with respect to the corresponding monomers.