Polarization-resolved extinction and scattering cross-section of individual gold nanoparticles measured by wide-field microscopy on a large ensemble

TL;DR

This paper introduces a rapid, cost-effective wide-field microscopy method to measure optical extinction and scattering cross-sections of individual nanoparticles, enabling statistical analysis of large ensembles.

Contribution

The authors present a novel wide-field technique for simultaneous measurement of extinction and scattering cross-sections of many nanoparticles, including polarization-dependent characterization.

Findings

Measured gold nanoparticle cross-sections consistent with literature

Demonstrated polarization-dependent extinction measurements

Method applicable to various nanoparticle types

Abstract

We report a simple, rapid, and quantitative wide-field technique to measure the optical extinction $\sigma_{\rm ext}$ and scattering $\sigma_{\rm sca}$ cross-section of single nanoparticles using wide-field microscopy enabling simultaneous acquisition of hundreds of nanoparticles for statistical analysis. As a proof of principle, we measured nominally spherical gold nanoparticles of 40\,nm and 100\,nm diameter and found mean values and standard deviations of $\sigma_{\rm ext}$ and $\sigma_{\rm sca}$ consistent with previous literature. Switching from unpolarized to linearly polarized excitation, we measured $\sigma_{\rm ext}$ as a function of the polarization direction, and used it to characterize the asphericity of the nanoparticles. The method can be implemented cost-effectively on any conventional wide-field microscope and is applicable to any nanoparticles.