Electrochemical Biosensor Based On Novel Two-Dimensional Composites For Organophosphate Pesticide Detection

Organophosphate pesticides（OPs）,are extensively used worldwide to increase agricultural productivity,whereas the excessive use of pesticides may trigger contamination in ecosystems and pose a great potential human health threat.Hence,it is of significant importance to devise an ultra-sensitive and accurate assay for the rapid screening of pesticide residues.AChE-based biosensors have been developed for rapidly monitoring OPs compounds via enzymatic inhibition pathway,ascribed to their instrumental simplicity,moderate cost,high sensitivity,and selectivity.With the development of nanomaterials,the use of advanced nanotechnology for designing and constructing electrochemical sensing platforms has gradually evolved into a key technology in biochemical analysis.By modifying the surface of the electrode,the conductivity,sensitivity,electrochemical activity,biocompatibility and catalytic properties of the sensing interface will be improved,and the loading of biomolecules is increased to some extent.Recently,two dimensional（2D）nanomaterials have aroused intensive interest in constructing sensors due to their intriguing physicochemical properties and electronic properties.This paper aims to establish an efficient and sensitive electrochemical sensor based on two-dimensional nanocomposites for detecting OPs.Two-dimensional composites have been prepared and employed for fabricating acetylcholinesterase biosensor to improve the sensitivity and stability.The details and results are summarized as follows:（1）A novel electrochemical biosensor was designed for sensitive detection of organophosphate pesticides based on three-dimensional porous bimetallic alloy architecture with ultrathin nanowires（PdCo NWs,PdCu NWs,PdNi NWs）and monolayer MoS₂ nanosheet（m-MoS₂）.The bimetallic alloy NWs/m-MoS₂ nanomaterials were used as a sensing platform for electrochemical analysis of omethoate,a representative organophosphate pesticide,via acetylcholinesterase inhibition pathway.We demonstrated that all three bimetallic alloy NWs enhanced electrochemical responses of enzymatic biosensor,benefited from bimetallic synergistic action and porous structure.In particular,PdNi NWs outperformed other two bimetallic alloy.Moreover,PdNi NWs/m-MoS₂ as an electronic transducer is superior to the corresponding biosensor in the absence of monolayer MoS₂ nanosheet,which arise from synergistic signal amplification effect between different components.Under optimized conditions,the developed biosensor on the basis of PdNi NWs/m-MoS₂ shows outstanding performance for the electrochemical assay of omethoate,such as a wide linear range(10^-13 M¹0^-7 M),a low detection limit of0.05 pM at a signal-to-noise ratio of 3,high sensitivity and long-time stability.The results demonstrate that bimetallic alloy NWs/MoS₂ nanocomposites could be excellent transducers to promote electron transfer for the electrochemical reactions,holding great potentials in the construction of current and future biosensing devices.（2）Two-dimensional（2D）MoS₂ shows great potential in the areas of electrochemical sensors due to their ultrathin structure and predominant physicochemical properties.However,pristine 2D MoS₂ nanostructure exists inherent disadvantages such as the limited electrical conductivity,surface area and easy aggregation or restacking.Here,nitrogen-fluorine co-doped monolayer 2D MoS₂ nanosheet decorated with Ag nanoparticles（Ag NPs-N-F-MoS₂）nanocomposite is prepared and it exhibits superior conductivity,remarkable electron mobility and high electroactive surface area.The obtained Ag NPs-N-F-MoS₂ are employed as a sensing platform for the electrochemical determination of organophosphate pesticide,coupled with enzymatic inhibition.Under optimized conditions,the acetylcholinesterase（AChE）/amino functionalized carbon nanotubes（CNTs-NH₂）/Ag NPs-N-F-MoS₂ bioelectrode is superior in sensing performances for the detection of monocrotophos and chlorpyrifos,with wide linear ranges,low detection limit as low as 0.2 pM and 3 pM at a signal-to-noise ratio of 3,satisfactory selectivity,reproducibility and long-time storage stability.（3）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^-1110^-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^-1)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%）.