Construction Of Metal Organic Framework Loaded Fe Nanozyme And Its Application In Chlorpyrifos Detectio

Nanozyme is a kind of nanomaterial with catalytic function similar to natural enzyme,which has the advantages of low cost and high stability.Among them,nanozymes based on metal-organic framework（MOFs）have attracted much attention.This is not only due to its large specific surface area,adjustable pore structure and good biocompatibility,but also because its inorganic-organic hybrid structure can be designed to have different simulated enzyme activities.In addition,MOFs can be used to construct multi-enzyme cascades to better simulate natural enzymes.Multifunctional nanozyme are widely used in analytical chemistry,environmental treatment and disease treatment.However,compared with natural enzymes,nanozymes have unique advantages in preparation,storage and application,but still face the problem of low catalytic activity.In this paper,two kinds of metal-organic framework supported Fe nanozyme with high simulated enzyme activities were constructed,the relationship between their structure and performance was systematically studied,and their excellent catalytic performance was used for the highly sensitive detection of acetylcholinesterase（ACh E）and chlorpyrifos,as shown below:（1）Efficient detection of chlorpyrifos by simple preparation of single-atom iron nanozyme:In this study,a novel Ui O-66-NH₂-Fe³⁺single-atom nanozyme with good peroxidase activity was simply prepared by non-pyrolytic method for the detection of acetylcholinesterase and chlorpyrifos.Firstly,a metal-organic framework Ui O-66-NH₂ was synthesized.Secondly,Ui O-66-NH₂-Fe³⁺single-atom nanozyme were simply prepared by loading Ui O-66-NH₂ with Fe³⁺.Based on the interaction between Fe and N,Fe is in monatomic dispersion state in the material and has good peroxidase activity.Ui O-66-NH₂-Fe³⁺single-atom nanozyme catalyzes H₂O₂ to produce hydroxyl radical（·OH）,oxidizes substrate 3,3’,5,5’-tetramethylbenzidine（TMB）to ox TMB,thus producing colorimetric and ultraviolet absorption signals.When there is acetylcholinesterase in the system,acetylcholinesterase will catalyze the hydrolysis of thioacetylcholine to produce sulfhydryl choline,inhibit the peroxidase activity of Ui O-66-NH₂-Fe³⁺,and cause the decrease of ultraviolet absorbance.When chlorpyrifos is present,chlorpyrifos will inhibit the hydrolysis catalysis of acetylcholinesterase and maintain the high peroxidase activity of Ui O-66-NH₂-Fe³⁺,so as to realize the efficient detection of acetylcholinesterase and chlorpyrifos.The sensor platform has a wide linear range（ACh E:0.0013～5.3 m U/m L）and a low detection limit（ACh E:0.00044m U/m L;chlorpyrifos:0.67 ng/m L）.This study provides a simple and reliable method for the preparation of single-atom nanozyme which can simulate enzyme activity efficiently.（2）Construction of His@ZIF-8/Fe³⁺nanoenzyme sensor and highly sensitive detection of chlorpyrifos:In this work,a histidine（His）functionalized MOF supported Fe nanozyme(His@ZIF-8/Fe³⁺)was designed and synthesized.His functionalized His@ZIF-8 was rich in carboxyl and amino groups,which were combined with the Fe³⁺coordination to form stable iron-doped nanomaterials(His@ZIF-8/Fe³⁺).His functional design refers to the structure of natural enzymes,and the synthetic His@ZIF-8/Fe³⁺has excellent peroxidase activity.The nanozyme sensing platform based on His@ZIF-8/Fe³⁺can efficiently and sensitively detect AC h E and chlorpyrifos in actual samples（same principle as above）.The sensor has the advantages of wide linear range（0.00067～2 m U/m L）,low detection limit（0.00022 m U/m L）for ACh E and low detection limit（0.67 ng/m L）for chlorpyrifos.This design provides a reference for the preparation of high activity nano enzyme.