Near-field Probing of Optical Superchirality for Enhanced Bio-detection

TL;DR

This paper introduces a near-field optical probing method using plasmonic circularly polarised luminescence to detect ultra-thin layers of chiral molecules with higher sensitivity than traditional far-field techniques.

Contribution

It demonstrates the use of PCPL as a local probe for near-field chirality, enabling detection of monolayer quantities of chiral biomolecules, surpassing previous far-field based methods.

Findings

Successful detection of monolayer chiral peptides

Enhanced sensitivity over traditional far-field methods

Potential for improved nanometrology applications

Abstract

Nanophotonic platforms in theory uniquely enable < femtomoles of chiral biological and pharmaceutical molecules to be detected, through the highly localised changes in the chiral asymmetries of the near-fields that they induce. However, current chiral nanophotonic based strategies are intrinsically limited because they rely on far-field optical measurements that are sensitive to a much larger near-field volume, than that influenced by the chiral molecules. Consequently, they depend on detecting small changes in far-field optical response restricting detection sensitivities. Here we exploit an intriguing phenomenon, plasmonic circularly polarised luminescence (PCPL), which is an incisive local probe of near-field chirality. This allows chiral detection of monolayer quantities of a de novo designed peptide, which is not achieved with a far-field response. Our work demonstrates that by leveraging the capabilities of nanophotonic platforms with the near-field sensitivity of PCPL, optimal biomolecular detection performance can be achieved, opening new avenues for nanometrology.