Understanding the Coupling Mechanism of Gold Nanostructures by Finite-Difference Time-Domain Method

TL;DR

This paper uses FDTD simulations to analyze how gold nanorods interact electromagnetically in different configurations, revealing exponential coupling behaviors and field enhancements useful for tuning plasmonic properties.

Contribution

It provides a detailed computational study of plasmonic coupling in gold nanorods, highlighting exponential behavior and field enhancement effects in specific assembly configurations.

Findings

Exponential coupling behavior in nanorod dimers.

Enhanced electric fields in end-to-end configurations.

Simulation results align with experimental growth dynamics.

Abstract

Gold nanoparticle assemblies show a strong plasmonic response due to the combined effects of the individual nanoparticles' plasmon modes. Increasing the number of nanoparticles in structured assemblies leads to significant shifts in the optical and physical properties. We use Finite-Difference Time-Domain (FDTD) simulations to analyze the electromagnetic response of structurally ordered gold nanorods in monomer and dimer configurations. The plasmonic coupling between nanorods in monomers or dimers configurations provides a unique technique for tuning the spectrum intensity, spatial distribution, and polarisation of local electric fields within and surrounding nanostructures. Our study shows an exponential coupling behavior when two gold nanorods are assembled in end-to-end and side-by-side dimer configurations with a small separation distance. The maximum electric field in the gaps between adjacent nanorods in end-to-end dimer configuration describes a more significant enhancement factor than the individual gold nanorod. Our FDTD simulation on dimer in end-to-end assembly for small separation distance up to ~ 40 nm can well explain the observed experimental growth dynamics of gold nanorods.