An unusually sharp localized surface plasmon resonance (sLSPR) is observed for a monolayer of glass-supported silver nanocubes coated with a thin, 5-20 nm, Al2O3 film. The resonance becomes significantly narrower and stronger while losing optical anisotropy and sensitivity to the surroundings with increasing overlayer thickness. Surface-enhanced Raman scattering excitation profiles indicate an additional enhancement to the electric field brought in by the sLSPR. The resonance is thought to originate from a Fano-like constructive interference between the quadrupolar and dipolar LSPR modes in supported silver nanocubes leading to enhanced light extinction. This phenomenon is of significance for plasmon-induced charge-transfer processes in photovoltaics and catalysis.

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Journal Journal of Physical Chemistry Letters
Prezgot, D. (Daniel), Bottomley, A. (Adam), Coyle, J.P, & Ianoul, A.I. (2017). Unusually Sharp Localized Surface Plasmon Resonance in Supported Silver Nanocrystals with a Thin Dielectric Coating. Journal of Physical Chemistry Letters, 8(22), 5555–5558. doi:10.1021/acs.jpclett.7b02499