Generation of energetic (hot) electrons is an intrinsic property of any plasmonic nanostructure under illumination. Simultaneously, a striking advantage of metal nanocrystals over semiconductors lies in their very large absorption cross sections. Therefore, metal nanostructures with strong and tailored plasmonic resonances are very attractive for photocatalytic applications in which excited electrons play an important role. However, the central questions in the problem of plasmonic hot electrons are the number of optically excited energetic electrons in a nanocrystal and how to extract such electrons. Here we develop a theory describing the generation rates and the energy distributions of hot electrons in nanocrystals with various geometries [1-4]. In particular, we show that nanostructures with strong and extended plasmonic hot spots generate unusually large numbers of energetic electrons, which can be observed using the ultra-fast transient spectroscopy [2,4,5] as well as photochemistry. Hot-electron generation together with non-radiative plasmonic transfer [6] represent efficient methods to transfer and localize optical and photo-chemical energies.

1. A.O. Govorov, H. Zhang, V. Demir, and Y. K. Gun’ko, Nano Today, 9, 85 (2014).
2. H. Harutyunyan, A. B. F. Martinson, D. Rosenmann, L.K. Khorashad, L.V.Besteiro, A.O.Govorov, and G.P. Wiederrecht, Nature Nanotechnology 10, 770–774 (2015).
3. L.V. Besteiro, X.-T. Kong, Z. Wang, G. V. Hartland, A.O. Govorov, ACS Photonics, DOI: 10.1021/acsphotonics.7b00751 (2017).
4. M.E. Sykes, J. W. Stewart, G. M. Akselrod, X.-T. Kong, Z. Wang, D. J. Gosztola, A.B.F. Martinson, D. Rosenmann, M. H. Mikkelsen, A. O. Govorov, G. P. Wiederrecht, Nature Communications, 8, 986 (2017).
5. G.V. Hartland, L. Besteiro, P. Johns, A. O. Govorov, What’s so Hot about Electrons in Metal Nanoparticles? (perspective paper), ACS Energy Letters, 2, 1641–1653 (2017).
6. E.-M. Roller, L.V. Besteiro, C. Pupp, L. Khosravi Khorashad, A. O. Govorov, T.Liedl, Nature Physics, 13, 761-765 (2017).