High-speed imaging of surface-enhanced Raman scattering fluctuations from individual nanoparticles

Document Type

Article

Abstract

The concept of plasmonic hotspots is central to the interpretation of the surface-enhanced Raman scattering (SERS) effect. Although plasmonic hotspots are generally portrayed as static features, single-molecule SERS (SM-SERS) is marked by characteristic time-dependent fluctuations in signal intensity. The origin of those fluctuations can be assigned to a variety of dynamic and complex processes, including molecular adsorption or desorption, surface diffusion, molecular reorientation and metal surface reconstruction. Since each of these mechanisms simultaneously contributes to a fluctuating SERS signal, probing their relative impact in SM-SERS remains an experimental challenge. Here, we introduce a super-resolution imaging technique with an acquisition rate of 800,000 frames per second to probe the spatial and temporal features of the SM-SERS fluctuations from single silver nanoshells. The technique has a spatial resolution of ~7 nm. The images reveal short ~10 µs scattering events localized in various regions on a single nanoparticle. Remarkably, even a fully functionalized nanoparticle was ‘dark’ more than 98% of the time. The sporadic SERS emission suggests a transient hotspot formation mechanism driven by a random reconstruction of the metallic surface, an effect that dominates over any plasmonic resonance of the particle itself. Our results provide the SERS community with a high-speed experimental approach to study the fast dynamic properties of SM-SERS hotspots in typical room-temperature experimental conditions, with possible implications in catalysis and sensing.

Department(s)

Physics and Engineering

Publication Title

Nature Nanotechnology

Volume

14

Issue

10

First Page

981

Last Page

987

Publication Date

10-1-2019

DOI

10.1038/s41565-019-0535-6

ISSN

17483387

E-ISSN

17483395

PubMed ID

31527841

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