Metal-organic frameworks-derived MnO2/Mn3O4 microcuboids with hierarchically ordered nanosheets and Ti3C2 MXene/Au NPs composites for electrochemical pesticide detection.

Transition metal oxides (TMOs) derived from metal - organic frameworks (MOF) combined with two-dimensional (2D) transition metal carbides possibly pave an innovative pathway for designing promising biosensors. Herein, a novel electrochemical sensing platform has been fabricated for ultra-sensitive determination of organophosphorus pesticides (OPs), based on MOF-derived MnO2/Mn3O4 and Ti3C2 MXene/Au NPs composites. Remarkably, the three-dimensional (3D) MnO2/Mn3O4 hierarchical microcuboids derived from Mn-MOF are composed of vertically aligned, highly ordered nanosheets, and further combined with MXene/Au NPs yields synergistic signal amplification effect, with outstanding electrochemical performance, large specific surface area, and good environmental biocompatibility. Under the optimum conditions, the reported sensing platform AChE-Chit/MXene/Au NPs/MnO2/Mn3O4/GCE can be utilized to detect methamidophos in a broad concentration range (10-12-10-6 M), together with a good linearity (R = 0.995). Besides that, the biosensor possesses a low limit of detection (1.34 × 10-13 M), which far exceeds the maximum residue limits (MRLs) for methamidophos (0.01 mg/kg) established by European Union. Additionally, the feasibility of the proposed biosensor for detecting methamidophos in real samples has been demonstrated with excellent recoveries (95.2%-101.3%). Interestingly, the unique structures and remarkable properties of these composites make them attractive materials for various electrochemical sensors for monitoring either pesticide residuals or other environmentally deleterious chemicals.