Construction Of Heterostructure MOFs Composite Electrochemical Sensor And Its Application In Food Safety Detection

With the improvement of people's living standard,food safety has become the focus of today's society.In order to simply and quickly detect the content of food additives and pesticide residues in agricultural products,it is imperative to establish a fast and highly sensitive analytical method.Electrochemical analysis method has been widely used in the field of analysis and detection because of its advantages of simple,rapid,accurate and sensitive instrument.Metal-organic frameworks(MOFs)are a class of crystalline microporous materials composed of organic ligands and metal ions or clusters self-assembled by coordination bonds.Compared with other porous materials,MOFs have the advantages of topological diversity,high porosity and large specific surface area,so they are ideal materials for the construction of electrochemical sensors.However,MOFs usually have poor electrical conductivity and stability,which can greatly affect sensor performance.The composite of MOFs conductive materials can make up for these defects of MOFs,and their stability and catalytic performance can be further improved through structural design.In this paper,three kinds of heterostructure MOFs matrix composites were prepared and used as an electrochemical sensing platform for the detection of pesticide residues in food additives and agricultural products.The details are as follows:(1)The flower-like graphene/Cu O@Cu-metal-organic framework(GR/Cu O@Cu-MOFs)composite was used to construct a sensing platform for the detection of caffeic acid(CA).The composite was synthesized by self-template method,in which Cu O was not only used as template,but also provided Cu2+ for the growth of Cu-MOFs shell.Graphene as a petal greatly improves the stability and electrical conductivity of Cu O@Cu-BTC.GR/Cu O@Cu-BTC composites have unique structural characteristics,high specific surface area and good electrical conductivity and other advantages,showing superior electrocatalytic activity for the oxidation of CA.Under optimized conditions,the linear range of CA detection by this sensor is 0.020-10.0 ?mol/L,and the detection limit is 7.0nmol/L.In addition,this sensor has been successfully applied to the detection of CA in red wine samples.(2)The core-shell structure of Cu@C@ZIF-8 composite was used to construct a sensing platform for the detection of nitrite.Based on the different thermal stability of Cu-MOFs and ZIF-8,Cu@C@ZIF-8 composite with core-shell structure was prepared by one-step pyrolysis.For the Cu@C@ZIF-8 sensor system,the ZIF-8 has a suitable aperture,which allows nitrites to pass through the ZIF-8 shell,while the macromolecules cannot,thus ensuring the high selectivity of the sensor.On the other hand,Cu@C acts as an electrocatalyst to promote the oxidation of nitrite,thus giving the sensor a high sensitivity.Under the optimized conditions,the linear range of nitrite detection by the sensor is 0.1?mol /L-300 ?mol/L,and the detection limit is 0.033 ?mol/L.(3)The layered MXene/CNH/?-CD-MOFs composite was used to construct a sensing platform for the detection of carbendazim.The host and guest recognition characteristics of?-CD,combined with the porous structure,high porosity and pore volume of MOFs,enable ?-CD-MOFs to have a high adsorption capacity for CBZ.The large specific surface area,large number of active sites and high electrical conductivity of MXene/CNH can provide more mass transfer channels.Under optimized conditions,the linear range of carbendazim detection was 3.0 nmol/L to 10.0 ?mol/L,and the detection limit was 1.0nmol/L.In addition,the sensor can be used for the detection of CBZ in tomato samples.