Quantitatively linking morphology and optical response of individual silver nanohedra

TL;DR

This study quantitatively links the 3D morphology of individual silver nanohedra to their optical responses by combining electron tomography, micro-spectroscopy, and simulations, revealing surface tarnish effects.

Contribution

It introduces a method integrating electron tomography and optical spectroscopy for precise correlation of nanoparticle morphology and optical properties.

Findings

Measured and simulated spectra match when accounting for surface tarnish.

Surface tarnish significantly affects optical response predictions.

Method enables predictive design of plasmonic nanomaterials.

Abstract

The optical response of metal nanoparticles is governed by plasmonic resonances, which are dictated by the particle morphology. A thorough understanding of the link between morphology and optical response requires quantitatively measuring optical and structural properties of the same particle. Here we present such a study, correlating electron tomography and optical micro-spectroscopy. The optical measurements determine the scattering and absorption cross-section spectra in absolute units, and electron tomography determines the 3D morphology. Numerical simulations of the spectra for the individual particle geometry, and the specific optical setup used, allow for a quantitative comparison including the cross-section magnitude. Silver nanoparticles produced by photochemically driven colloidal synthesis, including decahedra, tetrahedra and bi-tetrahedra are investigated. A mismatch of measured and simulated spectra is found when assuming pure silver particles, which is resolved by the presence of a few atomic layers of tarnish on the surface, not evident in electron tomography. The presented method tightens the link between particle morphology and optical response, supporting the predictive design of plasmonic nanomaterials.