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

TL;DR

This study investigates the localized surface plasmon resonances of trisoctahedral gold nanocrystals and their significant enhancement of Raman scattering, highlighting the importance of nanogaps in SERS applications.

Contribution

The paper provides high-resolution spatial analysis of LSPR modes in TOH gold nanocrystals and demonstrates their superior SERS activity due to nanogap hotspots.

Findings

Pronounced SERS enhancement observed with TOH gold nanocrystals.

Nanogaps between nanoparticles create stronger hot spots for SERS.

Aggregates outperform individual nanoparticles in SERS applications.

Abstract

Trisoctahedral (TOH) shaped Au nanocrystals (NCs) have emerged as a new class of metal nanoparticles (MNP) due to its superior catalystic and SERS activities caused by the presence of high density 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 of the local density of optical states (LDOS) across the visible spectral range. Further we show pronounced enhancement factor 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 hotspots may have crucial role on the substantial SERS enhancement observed in this report. Consequently, the present study indicates that MNPs aggregates are highly desirable than individual plasmonic nanoparticles for possible applications in SERS based biosensing.