Stable Core-Shell Structure Nanocrystals of Cs₄PbBr₆-Zn(moi)₂ Achieved by an In Situ Surface Reconstruction Strategy...

Zero-dimensional Cs₄PbBr₆ nanocrystals (NCs) possess attractive photoluminescence (PL) properties and feature facile chemical synthesis, making them promising for application in luminescent materials. However, Cs₄PbBr₆ remains sensitive to polar solvents and thermal stimuli because of soft ionic nature of Cs₄PbBr₆ and dynamic behavior of surface ligands. Herein, a strategy controlled by an in situ surface coordination reaction is developed to fabricate stable NCs with a Cs₄PbBr₆-Zn(moi)₂ core-shell structure. It was found that the Cs₄PbBr₆ surface regulated by the use of 2-mercaptoimidazole (called moi) and the coordination between the -NH group of moi and Zn²⁺ is critical for the formation of Cs₄PbBr₆-Zn(moi)₂ core-shell NCs. Meanwhile, the thickness of the Zn(moi)₂ shell can be facilely controlled by the growth time because of the solubility of moi and Zn(OAc)₂·2H₂O in ethyl acetate. Compared to bare Cs₄PbBr₆, Cs₄PbBr₆-Zn(moi)₂ NCs exhibited highly improved polar solvent resistance and thermal stability. By combining the sensitivity of Cs₄PbBr₆ and the stability of Cs₄PbBr₆-Zn(moi)₂, we used two NCs as PL security inks to fabricate optical anticounterfeiting labels. Thus, the disposable or reusable optical anticounterfeiting label is achieved by changing the external dual-stimuli. This work provides a novel strategy to enhance the stability of Cs₄PbBr₆ and develop its potential interest for application in anticounterfeiting technologies.