Plasmofluidic Single-Molecule Surface Enhanced Raman Scattering from Dynamic Assembly of Plasmonic Nanoparticles

TL;DR

This paper introduces a reversible, optically controlled method for assembling plasmonic nanoparticles at a metal-fluid interface to enhance single-molecule Raman scattering, enabling dynamic and re-dispersible detection platforms.

Contribution

It demonstrates a novel, single-beam, plasmon-polariton assisted assembly technique for SM-SERS, allowing reversible nanoparticle aggregation and dynamic manipulation at an unstructured interface.

Findings

Reversible nanoparticle assembly enhances SM-SERS sensitivity.

Dual excitation creates interacting nanoparticle assemblies.

Method enables optically addressable, dynamic nanostructure lithography.

Abstract

Single-molecule surface enhanced Raman scattering (SM-SERS) is one of the vital applications of plasmonic nanoparticles. The SM-SERS sensitivity critically depends on plasmonic hot-spots created at the vicinity of such nanoparticles. In conventional fluid-phase SM-SERS experiments, plasmonic hot-spots are facilitated by chemical aggregation of nanoparticles. Such aggregation is usually irreversible, and hence, nanoparticles cannot be re-dispersed in the fluid for further use. Here, we show how to combine SM-SERS with plasmon-polariton assisted, reversible assembly of plasmonic nanoparticles at an unstructured metal-fluid interface. One of the unique features of our method is that we use a single evanescent-wave optical excitation for nanoparticle-assembly, manipulation and SM-SERS measurements. Furthermore, by utilizing dual excitation of plasmons at metal-fluid interface, we create interacting assemblies of metal nanoparticles, which may be further harnessed in dynamic lithography of dispersed nanostructures. Our work will have implications in realizing optically addressable, plasmofluidic, single-molecule detection platforms.