Large Enhancement of Circular Dichroism Using an Embossed Chiral Metamaterial

TL;DR

This paper demonstrates a significant enhancement of circular dichroism signals by using an embossed chiral metamaterial, enabling sensitive detection of biomolecules at the molecular level through surface-enhanced chiroptical effects.

Contribution

It introduces a novel embossed chiral nanostructure that achieves on-resonance surface-enhanced circular dichroism, surpassing previous modest enhancements with planar structures.

Findings

Achieved unprecedented large differential CD spectrum from a monolayer

Demonstrated on-resonance enhancement by matching chiral resonances

Measured CD spectra of Chlorophylls A and B at the molecular level

Abstract

In the close vicinity of a chiral nanostructure, the circular dichroism of a biomolecule could be greatly enhanced, due to the interaction with the local superchiral fields. Modest enhancement of optical activity using a planar metamaterial, with some chiral properties, and achiral nanoparticles has been previously reported. A more substantial chirality enhancement can be achieved in the local filed of a chiral nanostructure with a three-dimensional arrangement. Using an embossed chiral nanostructure designed for chiroptical sensing, we measure the circular dichroism spectra of two biomolecules, Chlorophylls A and B, at the molecular level, using a simple polarization resolved reflection measurement. This experiment is the first realization of the on-resonance surface-enhanced circular dichroism, achieved by matching the chiral resonances of a strongly chiral metamaterial with that of a chiral molecule, resulting in an unprecedentedly large differential CD spectrum from a monolayer of a chiral material.