An Electron Transfer Regulation Strategy to Enhance the Catalytic Activity of Perovskite Fluorescent Nanozyme by Incorporation of Fe Metal-organic Framework for Biomimetic Cascade Catalysis.

Fluorescent nanozymes allow the use of both fluorescence and catalytic functions for theragnostic and bioanalytical applications. However, few fluorescent nanozymes with both high fluorescence yield and high catalytic activities are available. CsPbX3 perovskite nanocrystals (PNCs) have strong fluorescence but very weak catalytic activities. Here, a microenvironment electron transfer regulation strategy is proposed to enhance the nanozymatic activities and stability of PNCs through the incorporation of Fe metal-organic framework (MOF). By in suit growth of an amphiphilic polymer (octylamine-modified polyacrylic acid) capped PNCs on MOF, the oxidase (OXD)-like activity of PNCs is enhanced sevenfold. X-ray absorption near-edge structure (XANES) and extended X-ray absorption fine structure (EXAFS) characterizations revealed that forming the composition results in valence state shifts of the Fe atoms, indicating an electron transfer from PNCs to MOF enabled by the built-in electric field, which improved the catalytic activities. Moreover, the nanocomposite also displays peroxidase (POD)-like activity, and its dual enzyme-like catalytic mechanism and activities are studied experimentally and theoretically. At last, a nanozyme cascade catalytic system based on the dual mimic enzyme of PNCs@MOF is constructed for ratiometric fluorescence biosensing of ascorbic acid with high sensitivity. This work provides an attractive fluorescent nanozyme, greatly expanding its application in bioanalysis.