Self assembly of highly fluorescent semiconductor nanorods into large scale smectic liquid crystal structures by coffee stain evaporation dynamics

TL;DR

This study demonstrates that evaporating droplets of semiconductor nanorods can self-assemble into large-scale, ordered smectic liquid crystal structures with specific optical properties, driven by coffee stain evaporation dynamics.

Contribution

It reveals the formation of highly ordered nanorod assemblies with birefringence, advancing understanding of self-assembly in evaporative processes.

Findings

Nanorods form dense, ordered structures within coffee stain fringes.

The nanorods' long axes align parallel to the contact line.

Birefringence indicates anisotropic optical properties of the assembled structures.

Abstract

We deposit droplets of nanorods dispersed in solvents on substrate surfaces and let the solvent evaporate. We find that strong contact line pinning leads to dense nanorod deposition inside coffee stain fringes, where we observe large-scale lateral ordering of the nanorods with the long axis of the rods oriented parallel to the contact line. We observe birefringence of these coffee stain fringes by polarized microscopy and we find the direction of the extraordinary refractive index parallel to the long axis of the nanorods.