Chirality Amplification and Detection by Tactoids of Lyotropic Chromonic Liquid Crystals

TL;DR

This paper demonstrates how lyotropic chromonic liquid crystals can amplify and visualize molecular chirality over micrometer scales, enabling easy detection of chiral molecules through tactoid-induced structural handedness.

Contribution

It introduces a novel mechanism of chirality amplification in water solutions of achiral molecules via tactoids in lyotropic chromonic liquid crystals, observable with simple microscopy.

Findings

Chiral molecules induce homochirality in tactoids.

Structural handedness is visually distinguishable under polarized light.

Amplification occurs over micrometer scales, larger than molecular.

Abstract

Detection of chiral molecules requires amplification of chirality to measurable levels. Typically, amplification mechanisms are considered at the microscopic scales of individual molecules and their aggregates. Here we demonstrate chirality amplification and visualization of structural handedness in water solutions of organic molecules that extends over the scale of many micrometers. The mechanism is rooted in the long-range elastic nature of orientational order in lyotropic chromonic liquid crystals (LCLCs) formed in water solutions of achiral disc-like molecules. The nematic LCLC coexists with its isotropic counterpart, forming elongated tactoids; spatial confinement causes structural twist even when the material is nonchiral. Minute quantities of chiral molecules such as amino acid L-alanine and limonene transform the racemic array of left- and right-twisted tactoids into a homochiral set. The left and right chiral enantiomers are readily distinguished from each other as the induced structural handedness is visualized through a simple polarizing microscope observation. The effect is important for developing our understanding of chirality amplification mechanisms; it also might open new possibilities in biosensing.