On the origin of chirality in plasmonic meta-molecules

TL;DR

This paper investigates the origin of chirality in plasmonic meta-molecules using DNA origami to assemble and analyze nanostructures, revealing new insights into chiral optical effects and coupling mechanisms.

Contribution

It introduces a method to precisely assemble plasmonic nanostructures with DNA origami, enabling detailed study of their chiral optical properties and uncovering chiral plasmonic-dielectric coupling phenomena.

Findings

Chiral signatures emerge when a third dimension is introduced.

Sign flipping signals are achieved by adding or removing single particles.

Chiral plasmonic-dielectric coupling explains complex electromagnetic interactions.

Abstract

Chirality is a fundamental feature in all domains of nature, ranging from particle physics over electromagnetism to chemistry and biology. Chiral objects lack a mirror plane and inversion symmetry and therefore cannot be spatially aligned with their mirrored counterpart, their enantiomer. Both natural molecules and artificial chiral nanostructures can be characterized by their light-matter interaction, which is reflected in circular dichroism (CD). Using DNA origami, we assemble model meta-molecules from multiple plasmonic nanoparticles, representing meta-atoms accurately positioned in space. This allows us to reconstruct piece by piece the impact of varying macromolecular geometries on their surrounding optical near fields. Next to the emergence of CD signatures in the instance that we architect a third dimension, we design and implement sign flipping signals through addition or removal of single particles in the artificial molecules. Our data and theoretical modelling reveal the hitherto unrecognized phenomenon of chiral plasmonic-dielectric coupling, explaining the intricate electromagnetic interactions within hybrid DNA-based plasmonic nanostructures.