Stable ultra-concentrated and ultra-dilute colloids of CsPbX3 (X=Cl, Br) nanocrystals using natural lecithin as a capping ligand

Krieg F, Ong QK, Burian M, Rainò G, Naumenko D, Amenitsch H, Süess A, Grotevent MJ, Krumeich F, Bodnarchuk MI, Shorubalko I, Stellacci F & Kovalenko MV

Journal of the American Chemical Society, 141(50), 19839-19849.

https://doi.org/10.1021/jacs.9b09969

Abstract

Attaining thermodynamic stability of colloids in a broad range of concentrations had long been a major thrust in the field of colloidal ligand-capped semiconductor nanocrystals (NCs). This challenge is particularly pressing for the novel NCs of cesium lead halide perovskites (CsPbX3; X=Cl, Br) owing to their highly dynamic and labile surfaces. Herein we demonstrate that soy-lecithin, a mass-produced natural phospholipid, serves as a tightly-binding surface capping ligand, suited for a high-reaction yield synthesis of CsPbX3 NCs (6-10 nm) and allowing for the long-term retention of colloidal and structural integrity of CsPbX3 NCs in a broad range of concentrations – from a few ng/mL to >400 mg/mL (inorganic core mass). The high colloidal stability achieved with this long-chain zwitterionic ligand can be rationalized with the Alexander-De Gennes model that considers the increased particle-particle repulsion due to branched chains and ligand polydispersity. The versatility and immense practical utility of such colloids is showcased by the single NC spectroscopy on ultra-dilute samples and, conversely, by obtaining micron-thick, optically homogeneous dense NC films in a single spin-coating step from ultra-concentrated colloids.