Single Molecule SERS in a Single Gold Nanoparticle-driven Thermoplasmonic Tweezer

TL;DR

This paper demonstrates single molecule SERS detection using a thermoplasmonic tweezer driven by a single gold nanoparticle, enabling sensitive, low-power trapping and manipulation of nanoparticles with potential biomedical applications.

Contribution

It introduces a novel low-power thermoplasmonic tweezer platform based on a single gold nanoparticle for single molecule detection and nanoparticle manipulation.

Findings

Achieved single molecule SERS signatures with low laser power (~0.1 mW/μm²).

Demonstrated trapping and transport of single gold nanoparticles and assemblies.

Identified critical parameters for thermoplasmonic sensitivity.

Abstract

Surface enhanced Raman scattering (SERS) is optically sensitive and chemically specific to detect single molecule spectroscopic signatures. Facilitating this capability in optically-trapped nanoparticles at low laser power remains a significant challenge. In this letter, we show single molecule SERS signatures in reversible assemblies of trapped plasmonic nanoparticles using a single laser excitation (633 nm). Importantly, this trap is facilitated by the thermoplasmonic field of a single gold nanoparticle dropcasted on a glass surface. We employ bi-analyte SERS technique to ascertain the single molecule statistical signatures, and identify the critical parameters of the thermoplasmonic tweezer that provide this sensitivity. Furthermore, we show the utility of this low power ($\approx$0.1 mW/$\mu$m^2) tweezer platform to trap single gold nanoparticle and transport assembly of nanoparticles. Given that our configuration is based on a dropcasted gold nanoparticle, we envisage its utility to create reconfigurable plasmonic metafluids in physiological and catalytic environments, and can be potentially adapted as an in-vivo plasmonic tweezer.