Sensitive fluorescence and visual detection of organophosphorus pesticides with a Ru(bpy)32+–ZIF-90–MnO2 sensing platform

Fluorescence sensing organophosphorus pesticides (OPs) is of great importance for both food safety and global environment; however, the reported fluorescent probes are usually directly exposed to the external environment, resulting in premature leakage or photobleaching and thus limiting their photostability and assay sensitivity. In this work, a fluorescent sensing platform consisting of a novel luminescent metal–organic framework (Ru(bpy)32+–ZIF-90) and manganese dioxide nanosheets (MnO2 NSs) was prepared for sensing OPs. Due to the protection and improvement in the fluorescence of Ru(bpy)32+ by ZIF-90, the Ru(bpy)32+–ZIF-90 probe displayed remarkable photostability and high stability in water. By virtue of the high stability of Ru(bpy)32+–ZIF-90, as well as the outstanding fluorescence quenching and notable recognition ability of the MnO2 NSs, this sensing platform provided excellent detection capability for parathion-methyl, with a wide concentration range of 0.050–60 ng mL−1 and a low detection limit of 0.037 ng mL−1. Additionally, the system exhibited a visual color change with the concentration of the OPs under sunlight. Moreover, satisfactory recoveries ranging from 93.3% to 103.6% were obtained for the real samples. The results indicated that the Ru(bpy)32+–ZIF-90–MnO2-based OP sensing platform is promising for applications in food safety and environmental monitoring.