Chiral multinary quantum dots through composition control: Toward next-generation semiconductor nanomaterials.

Chirality is a fundamental property of matter with far-reaching implications in chemistry, biology, and materials science. The emergence of chirality in inorganic nanomaterials has attracted growing attention due to both its fundamental significance for the design of novel nanostructures with unprecedented control on morphology and properties, as well as for its intrinsic potential in advanced applications. Herein, we report a novel strategy for the design of chiral nanomaterials by exploiting the precise tuning of the chemical composition of the nanocrystal. In this way, we successfully optimized the chiroptical activity in a broad compositional space of ternary and quaternary I-III-VI quantum dots (QDs) based on silver, copper, and indium sulfides. Our research reveals a clear threshold for chirality in relation to the chemical composition of the luminescent multinary nanocrystals. In particular, the magnitude of the chiroptical activity is directly related to the trivalent indium content, and only QDs produced in the compositional space of the indium-rich MIn₅S₈ phases M = Ag, Cu exhibit chiroptical activity, whereas the indium-poor MInS₂ counterparts remain consistently achiral. This compositional control of chirality arises from the distinct surface coordination environments, which govern the binding affinity and orientation of the chiral ligands on the QDs' surface, as demonstrated by computational studies. These findings establish a detailed mechanism for chirality induction in excitonic semiconductor nanomaterials and offer new design strategies for engineering chiral QDs through targeted control of their composition and surface chemistry.