Asynchronous Preparation of Host—Guest Structures Enabling In Situ Growth of CsPbBr3: A Key to Forming Confined Perovskite and Its Application in Mercury (II) Ion Detection

A significant challenge persists in the form of poor long-term stability of metal halide perovskites under ambient conditions, which has substantially impeded their practical implementation in the field of sensing applications. Herein, CsPbBr₃ with a good water stability has been successfully synthesized within the confined nanospace of a ZIF-8. The synthesized material, denoted as CsPbBr₃@ZIF-8, was fabricated with ultrafine CsPbBr₃ perovskite particles having an average radius of 5 nm. Benefiting from the outstanding optical properties and remarkable water stability of CsPbBr₃@ZIF-8, a fluorescent quenching-based sensing platform for the detection of Hg²⁺ ions in aqueous solutions has been established. This platform relies on direct chemical reactions and features an impressively low detection limit of 8.25 nM, along with a broad linear quantification range spanning from 10 to 5000 nM. The mechanism underlying the fluorescence quenching of CsPbBr₃@ZIF-8 by Hg²⁺ ions was elucidated as photo-induced electron transfer. This conclusion was drawn by comparing the discrepancies in the fluorescence lifetimes of CsPbBr₃@ZIF-8 before and after the introduction of Hg²⁺ ions. This innovative approach not only enhanced the stability of the CsPbBr₃ nanocrystals but also opened up new possibilities for their application in various sensing scenarios where aqueous environments are involved.