Flickering nanometre-scale disorder in a crystal lattice tracked by plasmonic flare light emission

Abstract

The dynamic restructuring of metal nanoparticle surfaces is known to greatly influence their catalytic, electronic transport, and chemical binding functionalities. Here we show for the first time that non-equilibrium atomic-scale lattice defects can be detected in nanoparticles by purely optical means. These fluctuating states determine interface electronic transport for molecular electronics but because such rearrangements are low energy, measuring their rapid dynamics on single nanostructures by X-rays, electron beams, or tunnelling microscopies, is invasive and damaging. We utilise nano-optics at the sub-5nm scale to reveal rapid (on the millisecond timescale) evolution of defect morphologies on facets of gold nanoparticles on a mirror. Besides dynamic structural information, this highlights fundamental questions about defining bulk plasma frequencies for metals probed at the nanoscale.

Nanoscopy through a plasmonic nanolens

“…4D). Another hypothesis for the revivals is migrating Au adatoms that can trap light into picocavities close to single molecules (10,48) or transient defects in the Au facets that depress the local plasma frequency, resulting in large enhancements of electronic Raman emission (49). Such transient phenomena can also lead to the SERRS peaks observed (SI Appendix, Fig.…”

Cascaded nanooptics to probe microsecond atomic-scale phenomena

“…A second phenomenon observed is the fleeting reconstruction of nanoscale patches on the gold facet surfaces inside the plasmonic hot spot, which are seen as brief local increases in the background SERS signal from free electrons in the metal, which we recently reported (53) and are referred to here as "flares." Even previous high-speed SERS measurements (with 10-ms acquisition times) (18,34,53) have averaged over such dynamics, but these can now be clearly resolved (Fig. 4B).…”

Intrinsic luminescence blinking from plasmonic nanojunctions

“…The generation of photo-excited charge carriers inside the metal can be enhanced by the plasmonic resonance and field enhancement, with potential applications in photo-catalysis 12 – 14 and nanoscale light sources 7 . Despite progress in developing plasmonic nanojunctions as a universal platform to engineer light–matter interaction at the nanoscale, the realization of their full potential is hindered by a limited understanding of physical processes driven by the tightly confined optical fields at the atomic scale 3 , 10 , 15 – 20 . Moreover, the modification of plasmon damping 21 , 22 and charge carrier dynamics 23 , 24 by metal–molecule interfaces and intrinsic grain boundaries 25 can further complicate the understanding of plasmonic nanojunctions.…”