Porous Core/Shell CoOOH Nanozymes-Enabled Glow-Type Chemiluminescence Coupled with ZIF-8@Fluorescein for Ratiometric Detection of Organophosphorus Pesticides

Classical luminol-H₂O₂ chemiluminescence (CL) systems exhibit notable limitations for point-of-care (POC) detection, including weak luminescence intensity and short emission duration as well as insufficient selectivity for the detection of non-redox-active analytes. In the work described herein, we employed porous core/shell cobalt oxyhydroxide nanozymes to develop a novel glow-type CL system (porous core/shell CoOOH nanozyme-luminol-H₂O₂) with strong and long-lasting visual luminescence. Featuring highly exposed active sites, the nanozyme's porous core/shell structure regulates reactive oxygen species generation kinetics, enabling stable and continuous conversion of H₂O₂ to singlet oxygen (¹O₂), hydroxyl radical (^{^•}OH), and superoxide radical (^•O₂^-). The stably released ¹O₂ reacts with luminol to yield a strong visible CL signal, with sustained luminescence persisting for 5 to 30 min (signal decay <5.0%) and the visible signal enduring for a total of 50 min. Meanwhile, by utilizing ZIF-8 for efficient encapsulation of fluorescein, the selective release triggered by the organophosphorus pesticide glyphosate (Glyp) enables energy transfer from excited 3-aminophthalate, thereby inducing an emission shift from 425 nm (blue) to 530 nm (yellow-green) to construct a visual ratiometric CL system. The ratiometric CL response is expansively linear in the 0.34-67.6 ppm range with a limit of detection of 0.03 ppm toward Glyp. Furthermore, a self-designed portable smartphone sensing platform was successfully used for quantitative result outputs, validating this novel strategy for POC pesticide monitoring.