Circular Dichroism of Single Particles

TL;DR

This paper demonstrates the direct measurement of circular dichroism in individual nano-objects using far field extinction microscopy, revealing sensitivity to small structural variations at the nanoscale.

Contribution

It introduces a novel method for observing CD in single nano-objects, overcoming limitations of traditional bulk measurements.

Findings

Successful measurement of CD in chiral nanostructures and nanocrystals

First direct observation of CD in individual nano-objects via far field microscopy

Enhanced understanding of nano-scale chiroptical effects

Abstract

Circular dichroism (CD), induced by chirality, is an important tool for manipulating light or for characterizing morphology of molecules, proteins, crystals and nano-structures. CD is manifested over a wide size-range, from molecules to crystals or large nanostructures. Being a weak phenomenon (small fraction of absorption), CD is routinely measured on macroscopic amount of matter in solution, crystals, or arrays of fabricated meta-particles. These measurements mask the sensitivity of CD to small structural variation in nano-objects. Recently, several groups reported on chiroptical effects in individual nanoscale objects: Some, using near-field microscopy, where the tip-object interaction requires consideration. Some, using dark field scattering on large objects, and others by monitoring the fluorescence of individual chiral molecules. Here, we report on the direct observation of CD in individual nano-objects by far field extinction microscopy. CD measurements of both chiral shaped nanostructures (Gammadions) and nanocrystals (HgS) with chiral lattice structure are reported.