Giant circular dichroism of a molecule in a region of strong plasmon resonances between two neighboring gold nanocrystals

TL;DR

This paper demonstrates theoretically that giant circular dichroism signals can be achieved in molecules placed in plasmonic hot spots between gold nanocrystals, by leveraging enhanced Coulomb interactions in the visible spectrum.

Contribution

It introduces a model showing how plasmonic resonances can significantly enhance molecular CD signals in the visible range, which is novel compared to traditional UV-range CD.

Findings

Giant molecular CD can be created in the visible spectrum.

Plasmonic hot spots amplify Coulomb interactions leading to enhanced CD.

Theoretical demonstration of strong CD enhancement in a plasmonic dimer setup.

Abstract

We report on giant circular dichroism (CD) of a molecule inserted into a plasmonic hot spot. Naturally occurring molecules and biomolecules have typically CD signals in the UV range, whereas plasmonic nanocrystals exhibit strong plasmon resonances in the visible spectral interval. Therefore, excitations of chiral molecules and plasmon resonances are typically off-resonant. Nevertheless, we demonstrate theoretically that it is possible to create strongly-enhanced molecular CD utilizing the plasmons. This task is doubly challenging since it requires both creation and enhancement of the molecular CD in the visible region. We demonstrate this effect within the model which incorporates a chiral molecule and a plasmonic dimer. The associated mechanism of plasmonic CD comes from the Coulomb interaction which is greatly amplified in a plasmonic hot spot.