Chromium(VI) contamination poses severe threats to ecosystems and human health. Therefore, it is urgently needed to develop efficient, sensitive, and reliable detection methods. In this work, a nanozyme-based ratiometric fluorescence platform was developed for high-performance Cr(VI) sensing by using an engineered composite (A@FeTImp@ZIF-8). This composite, classified as a molecule@support material, was fabricated by grafting 5, 10, 15, 20-Tetrakis(4-(imidazol-1-yl) phenyl) iron porphyrin (FeTImp) onto zeolitic imidazolate framework-8 (ZIF-8) surfaces via a simple ligand exchange reaction. The resulting A@FeTImp@ZIF-8 composite exhibited enhanced peroxidase-mimicking activity alongside intrinsic fluorescence properties. Under H 2 O 2 activation, A@FeTImp@ZIF-8 catalyzes the oxidation of o-phenylenediamine (OPD) to fluorescent 2,3-diaminophenazine (DAP, emission at 565 nm). The generated DAP subsequently quenches acridine (A) fluorescence signal (435 nm) via an inner filter effect (IFE). The addition of 8-hydroxyquinoline (8-HQ) competitively inhibits OPD oxidation, leading to a decrease in the DAP signal (565 nm) and a recovery of the A fluorescence (435 nm). Upon introduction of Cr(VI), it complexes with 8-HQ, reactivating the OPD oxidation process. By utilizing these synergistic effects, a highly sensitive and selective detection of Cr(VI) was achieved over a wide linear range (0.01–180 μM), with an ultra-low detection limit of 3.74 nM (S/N = 3). The sensor was also successfully applied to monitor Cr(VI) in environmental water samples. • An IFE-based ratiometric fluorescent biosensor was developed for sensitive Cr(VI) detection. • A@FeTImp@ZIF-8 was fabricated via ligand exchange, ensuring precise catalyst immobilization. • The composite integrates FeTImp as a peroxidase mimic and acridine as a fluorophore. • A stable dual-emission signal enables reliable and sensitive sensing.
Duan et al. (Mon,) studied this question.