El Ectrochemical Sensors Based On Bimetallic MOFs Derivatives And Detection Of Organophosphorus Pesticides

In order to ensure the effective supply of national agricultural products,solve the problem of food shortage,and prevent and control the major diseases and pests of crops,China’s agricultural production is forced to rely on a large amount of chemical fertilizers and pesticides,resulting in serious problems of food safety and ecological environment pollution.Therefore,pesticide residue detection is very urgent.Electrochemical sensors have become an important means of analysis and detection of agricultural residues because of their low production cost,rapid detection and simple operation.Using advanced nanotechnology to synthesize nanomaterials with excellent conductivity,good biocompatibility and large specific surface area can greatly improve the electrochemical performance of the sensing interface.Therefore,the design and synthesis of advanced nanomaterials is one of the key technologies for the construction of sensing platforms.In recent years,organometallic framework（MOF）and its derived materials（sulfide,nitrides,phosphide and oxides,etc.）have been widely concerned because of their adjustable structure and high porosity.In particular,MOFs-derived bimetallic oxides are attracting much attention in the construction of sensors due to their unique structure and synergies between different metals.In this study,MOFs-derived Mn Co₂O_4.5,Ni Co₂O₄-Co₃O₄/N-F-GDY materials were synthesized.Based on these advanced materials,a series of electrochemical sensors for acetylcholinesterase（ACh E）were constructed.By using the enzyme inhibition principle,rapid and sensitive detection of organophosphorus pesticides such as monocrotomophos and methamidophos was realized.The research contents and conclusions are as follows:（1）Co-Mn-MOF was synthesized in one step by hydrothermal synthesis method,and was used as a template to prepare core-shell cobalt-manganese bimetallic oxides with different layers by high temperature calcination at different temperatures（300-500℃）.They are two layers(Mn Co₂O_4.5 Ho DS-MPs),three layers(Mn Co₂O_4.5 Ho TS-MPs)and four layers(Mn Co₂O_4.5 Ho QS-MPs).The electrochemical properties of different modified electrodes were characterized and compared by cyclic voltammetry,electrochemical impedance spectroscopy and differential pulse voltammetry.The results show that Mn Co₂O_4.5 Ho QS-MPs has the best electrochemical properties.An electrochemical biosensor platform(ACh E-NF/Mn Co₂O_4.5 Ho QS-MPs/GCE)was constructed based on the material to detect and analyze methamidophos and monocrotophos.Under optimal experimental conditions,the linear ranges of monocrotophos and methamidophos detected by the sensor are 4.48×10^-13 M-4.48×10^-7 M and 7.085×10^-13 M-7.085×10^-8 M,respectively.The limits of detection were 1.82×10^-14 M and 1.66×10^-14 M,respectively.The recovery rate of the system is 90.0-115.6%,which proves that the constructed sensor has certain operational reliability.（2）ZIF-67 was synthesized by direct synthesis method,and was used as a precursor to obtain Co-Ni-LDH by chemical etching with Ni²⁺.Then,cobalt-Ni oxide with unique hollow core-shell structure was obtained by high temperature calcination.When nitrogen and fluorine nonmetallic atoms are doped into graphite-alkyne by calcination at high temperature in an inert atmosphere,the introduction of nonmetallic heteroatoms leads to more defects and abundant active sites.Based on the synergistic amplification of the two materials,an electrochemical biosensor platform（ACh E-NF/Ni Co₂O₄-Co₃O₄/N-F-GDY/GCE）was constructed to detect and analyze monocrotophos.The linear range of monocrotophos detected by this sensor is 4.48×10^-13 M-4.48×10^-8 M,and the detection limit（LOD）is 1.66×10^-14 M.The recovery rate of the system is 102-110%,which proves that the constructed sensor has practical operability.