A ratiometric fluorescence sensor for detection of organophosphorus pesticides based on enzyme-regulated multifunctional Fe-based metal-organic framework

The residues of organophosphorus pesticides (OPs) are increasing environmental pollution and public health concerns. Thus, the development of simple, convenient and sensitive method for detection of OPs is crucial. Herein, a multifunctional Fe-based MOF with fluorescence, catalytic and adsorption, is synthesized by a simple one-pot hydrothermal method. The ratiometric fluorescence sensor for detection of OPs is constructed by using only one multifunctional sensing material. The NH2-MIL-101(Fe) is able catalyze the o-phenylenediamine (OPD) into 2,3-diaminophenazine (DAP) in the presence of H2O2. The generated DAP can significantly quench the intrinsic fluorescence of NH2-MIL-101(Fe) by the fluorescence resonance energy transfer (FRET) and internal filtration effect (IFE), while producing a new measurable fluorescence. Without immobilization or molecular imprinting, pyrophosphate ion (PPi) can inhibit the peroxidase-like activity of the NH2-MIL-101(Fe) by chelating with Fe3+/Fe2+ redox couple. Moreover, PPi can also be hydrolyzed by alkaline phosphatase (ALP), the presence of OPs inhibits the activity of ALP, resulting in the increase of extra PPi preservation and signal changes of ratiometric fluorescence, the interactions of ALP with different OPs are explored by molecular docking, the OPs (e.g., glyphosate) interact with crucial amino acid residues (Asp, Ser, Ala, Lys and Arg) are indicated. The proposed sensor exhibits excellent detection performance for OPs with the detection limit of 18.7 nM, which provides a promising strategy for detection of OPs.