Impact of particle-size polydispersity on the quality of thin-film colloidal crystals

TL;DR

This study experimentally investigates how increasing size polydispersity in colloidal particles affects the structural order of thin-film colloidal crystals, revealing critical limits for maintaining crystalline quality.

Contribution

It provides systematic experimental data on the impact of polydispersity on colloidal crystal order, complementing prior computational studies.

Findings

Order deteriorates significantly at 8% and 12% polydispersity.

Results support models of epitaxial-like growth during assembly.

Insights into limits for sustainable colloidal crystal synthesis.

Abstract

Size polydispersity in colloidal particles can disrupt order in their self-assembly, ultimately leading to a complete suppression of crystallization. In contrast to various computational studies, few experimental studies systematically address the effects of size polydispersity on the quality of colloidal crystals. We present an experimental study of structural order in thin films of crystals vertically dried from colloidal dispersions with a systematically varying polydispersity. As expected, an increase in polydispersity leads to a deterioration in order with significant drops in the local bond-orientational order at 8% and 12% polydispersity. Our results align with previously suggested models of epitaxial-like growth of 2D layers during convective assembly. Our results can offer critical insights into the permissible limits for achieving colloidal crystals from more polydisperse systems such as those synthesized through more sustainable methods.