Probing Localized Surface Plasmons of Trisoctahedral Gold Nanocrystals for Surface Enhanced Raman Scattering

Trisoctahedral (TOH) shaped gold (Au) nanocrystals (NCs) have emerged as a new class of metal nanoparticles (MNPs) due to their superior catalytic and surface enhanced Raman scattering (SERS) activities caused by the presence of high density of atomic steps and dangling bonds on their high-index facets. We examine the radiative localized surface plasmon resonance (LSPR) modes of an isolated single TOH Au NC using cathodoluminescence (CL), with high resolution spatial information on the local density of optical states (LDOS) across the visible spectral range. Further, we show pronounced enhancement in the Raman scattering by performing Raman spectroscopic measurements on Rhodamine 6G (R6G)-covered TOH Au NPs aggregates on a Si substrate. We believe that the hot spots between two adjacent MNP surfaces (“nanogaps”) can be significantly stronger than single particle LSPRs. Such “nanogaps” hot spots may have crucial role on the substantial SERS enhancement observed in this report. Consequently, the present stu...