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Direct optical excitation of dark plasmons for hot electron generation

Abstract

An ideal plasmonic system for hot-electron generation allows the optical excitation of plasmons, limits radiation losses, shows strong non-radiative electron damping, and is made from scalable and cost effective materials. Here we demonstrate the optical excitation of dark interlayer plasmons in bilayers of colloidal gold nanoparticles. This excitation is created by an antiparallel orientation of the dipole moments in the nanoparticle layers; it is expected to have a strongly reduced radiative damping. Despite the vanishing dipole moment, an incoming electromagnetic wave that is propagating normal to the surface will excite the dark mode due to field retardation. We measure a strong peak in the absorption spectrum of a colloidal gold bilayer (nanoparticle diameter = 46 nm); the peak is absent for a nanoparticle monolayer. The full width at half maximum of the dark mode is 230 meV for an ideal nanoparticle crystal and 320 meV for the structure produced by self-assembly out of solution. Position and width of the dark plasmon are efficiently tailored by the interparticle distance within the layer, nanoparticle size, and layer number. We present time-resolved pump and probe experiments of hot-electron generation by the bright and the dark bilayer nanoparticle mode.

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Publication details

The article was accepted on 12 Nov 2018 and first published on 12 Nov 2018


Article type: Paper
DOI: 10.1039/C8FD00149A
Citation: Faraday Discuss., 2018, Accepted Manuscript
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    Direct optical excitation of dark plasmons for hot electron generation

    N. S. Mueller, B. G. M. Vieira, D. Höing, F. Schulz, E. B. Barros, H. Lange and S. Reich, Faraday Discuss., 2018, Accepted Manuscript , DOI: 10.1039/C8FD00149A

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