Optically and elastically assembled plasmonic nanoantennae for spatially resolved characterization of chemical composition in soft matter systems using surface enhanced spontaneous and stimulated Raman scattering

TL;DR

This paper introduces a method using optically controlled plasmonic nanoantennae assembled by laser tweezers to spatially resolve chemical composition in soft matter via enhanced Raman scattering techniques.

Contribution

It presents a novel approach for local chemical analysis in soft matter using self-assembled plasmonic nanoantennae manipulated by optical trapping.

Findings

Enhanced Raman signals from nanoantennae enable detection of tiny organic molecules.

Reconfigurable nanoantennae allow spatial mapping of chemical composition.

Demonstrated applications include probing liquid crystal defects and nanoparticle ligands.

Abstract

We present a method to locally probe spatially varying chemical composition of soft matter systems by use of optically controlled and elastically self-assembled plasmonic nanoantennae. Disc-shaped metal particles with sharp irregular edges are optically trapped, manipulated, and assembled into small clusters to provide a strong enhancement of the Raman scattering signal coming from the sample regions around and in-between these particles. As the particles are reassembled and spatially translated by computer-controlled laser tweezers, we probe chemical composition as a function of spatial coordinates. This allows us to reliably detect tiny quantities of organic molecules, such as capping ligands present on various nanoparticles, as well as to probe chemical composition of the interior of liquid crystal defect cores that can be filled with, for example, polymer chains. The strong electromagnetic field enhancement of optically-manipulated nanoparticles rough surfaces is demonstrated in different forms of spectroscopy and microscopy, including enhanced spontaneous Raman scattering, coherent anti-Stokes Raman scattering, and stimulated Raman scattering imaging modes.