Plasmonic Manipulation of Sodium Chlorate Chiral Crystallization: Directed Chirality Transfer via Contact-Induced Polymorphic Transformation and Formation of Liquid Precursor

Abstract

The control of crystallization not only impacts the production of functional crystalline materials or pharmaceuticals but also provides profit to investigate the fundamental mechanism of crystallization. Recently, we have revealed that plasmonic optical tweezers (POT) can "manipulate" the crystallization of a pharmaceutical compound from its aqueous solution by optically trapping molecular clusters, offering a novel strategy to control crystallization. Here we report a variety of unique crystallization phenomena by applying POT to sodium chlorate (NaClO3) chiral crystallization from an aqueous microdroplet loaded on a plasmonic substrate. Plasmon excitation significantly promotes crystallization intermediated by an achiral metastable crystal as a precursor. Also, the direction of the creeping of the resulting chiral crystal can be controlled. By utilizing this phenomenon, we achieved the directed chirality transfer from the chiral crystal to the achiral crystal via a forced contact-induced polymorphic transformation by intentionally making creeping chiral crystal contact with an achiral crystal. Moreover, we captured, by in situ optical microscopic observation, a liquid precursor that intermediates the NaClO3 achiral crystallization for the first time. Our results highlight the plasmonic manipulation of crystallization opening a new door not only to control crystallization but also to investigate the unprecedented fundamental process of crystallization.