The presence of an excitonic element in close proximity of a plasmonic nanostructure, under certain conditions, may lead to a nonradiative resonant energy transfer known as Exciton Plasmon Resonant Energy Transfer (EPRET) process. The exciton-plasmon coupling and dynamics have been intensely studied in the last decade; still many relevant aspects need more in-depth studies. Understanding such phenomenon is not only important from fundamental viewpoint, but also essential to unlock many promising applications. In this review we investigate the plasmon-exciton resonant energy transfer in different hybrid systems at the nano- and mesoscales, in order to gain further understanding of such processes across scales and pave the way towards active plasmonic devices.
Inherent absorptive losses affect the performance of all plasmonic devices, limiting their fascinating applications in the visible range. Here, we report on the enhanced optical transparency obtained as a result of the broadband mitigation of optical losses in nanocomposite polymeric films, embedding core-shell quantum dots (CdSe@ZnS QDs) and gold nanoparticles (Au-NPs). Exciton-plasmon coupling enables non-radiative energy transfer processes from QDs to metal NPs, resulting in gain induced transparency of the hybrid flexible systems. Experimental evidences, such as fluorescence quenching and modifications of fluorescence lifetimes confirm the presence of this strong coupling between plexcitonic elements. Measures performed by means of an ultra-fast broadband pump-probe setup demonstrate loss compensation of gold NPs dispersed in plastic network in presence of gain. Furthermore, we compare two films containing different concentrations of gold NPs and same amount of QDs, to investigate the role of acceptor concentration (Au-NPs) in order to promote an effective and efficient energy transfer mechanism. Gain induced transparency in bulk systems represents a promising path towards the realization of loss compensated plasmonic devices.
The inherent and strong optical losses present in plasmonic nanostructures, significantly limits their technological applications at optical frequencies. Here, we report about the interplay between plasmons and excitons as a potential approach to selectively reduce ohmic losses. Samples have been 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 corresponding monomers. We have measured fluorophores emission quenching by means of steady-state fluorescence spectroscopy and as well as significant shortening of the corresponding fluorescence lifetime. These results were accompanied by simultaneous enhancement of Rayleigh scattering and transmittance, revealing an effective absorptive loss mitigation of the 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 excitonplasmon resonant energy transfer (EPRET) was significantly enhanced in both multimeric and monomeric samples. Simulations data along with experimental results confirm that the hybridized plasmon fields of multimers lead to more efficient optical loss compensation with respect to corresponding monomers.
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