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Light Harvesting and Energy Conversion with Surface Plasmon

Plasmons decay radiatively via scattering or non-radiatively generating an excited electron-hole pair. Unlike in semiconductors, where a large bandgap enables long carrier lifetimes, excited electrons and holes in metals relax much more quickly due to the large density of states. While short hot carrier lifetimes appear counterproductive for photo-initiated chemical reactions on the surface of metal nanoparticles, many reactions have been demonstrated as the enormous absorption cross sections offset short carrier lifetimes. Much new physics and chemistry is however still to be learned about hot carrier generation and subsequent transfer to electron and hole acceptors, possibly revolutionizing how we currently think about photocatalysis. The Link lab has been contributing to this field in several different ways. We have shown how the homogeneous plasmon linewidth obtained from single-particle measurements yields electron transfer times and efficiencies to a strong electron acceptor like graphene. We have developed single particle absorption spectroscopy based on photothermal imaging in order to determine the hot carrier generation efficiency free from background scattering for large nanostructures with bright and dark plasmon modes. We have discovered one-photon photoluminescence in gold nanorods, which presents a direct signature of the hot carrier distribution. Finally, we study the ultrafast relaxation dynamics of hot carriers directly through single particle ultrafast pump-probe spectroscopy. All these studies can furthermore be carried out in an electrochemical cell applying potentials that tune the Fermi level and give mechanistic insight into photo-initiated, electro-catalytic redox reactions for energy harvesting and storage applications.

Selected Publications:

    Y.-Y Cai, J. G. Liu, L. J. Tauzin, D. Huang, E. Sung, H. Zhang, A. Joplin, W.-S. Chang, P. Nordlander, S. Link Photoluminescence of Gold Nanorods: Purcell Effect Enhanced Emission from Hot Carriers. ACS Nano Article, ASAP.  link
    A. Joplin, W.-S. Chang, S. Link Imaging and Spectroscopy of Single Metal Nanostructure Absorption. Langmuir, ASAP. link
    M. Yorulmaz, A. R. Hoggard, H. Zhang, F. Wen, W.-S. Chang, N. J. Halas, P. Nordlander, S. Link Absorption Spectroscopy of an Individual Fano Cluster. Nano Letter, 16 (10), 6497 (2016). link

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