Twisted bilayer graphene for enantiomeric sensing of chiral molecules

TL;DR

This paper introduces a novel chiral sensing method using twisted bilayer graphene (TBG) that enhances circular dichroism interactions, enabling highly sensitive, spatially uniform detection of molecular chirality at the single-molecule level.

Contribution

The study presents a new approach employing TBG's tunable chiral properties to improve enantiomeric sensing without molecular functionalization, surpassing previous limitations.

Findings

TBG's CD resonance can be tuned via twist angle.

Resonant energy transfer enhances chiral molecule detection.

Single-molecule sensitivity demonstrated with TBG-based sensing.

Abstract

Selective sensing of chiral molecules is a key aspect in fields spanning biology, chemistry, and pharmacology. However, conventional optical methods, such as circular dichroism (CD), encounter limitations owing to weak chiral light-matter interactions. Several strategies have been investigated to enhance CD or circularly polarised luminescence (CPL), including superchiral light, plasmonic nanoresonators and dielectric nanostructures. However, a compromise between spatial uniformity and high sensitivity, without requiring specific molecular functionalization, remains a challenge. In this work, we propose a novel approach using twisted bilayer graphene (TBG), a chiral 2D material with a strong CD peak which energy is tunable through the twist angle. By matching the CD resonance of TBG with the optical transition energy of the molecule, we achieve a decay rate enhancement mediated by resonant energy transfer that depends on the electric-magnetic interaction, that is, on the chirality of both the molecules and TBG. This leads to an enantioselective quenching of the molecule fluorescence, allowing to retrieve the molecule chirality from time-resolved photoluminescence measurements. This method demonstrates high sensitivity down to single layer of molecules, with the potential to achieve the ultimate goal of single-molecule chirality sensing, while preserving the spatial uniformity and integrability of 2D heterostructures.