Construction Of Fluorescence Sensing Methods Based On Metal-Organic Framework And The Application To The Detection Of Pesticide Residues In Food

Pesticides are commonly used to meet the growing demand for agricultural production.However,food safety and environmental pollution have made pesticide detection a critical issue.Gas chromatography,high performance liquid chromatography,gas chromatography-mass spectrometry,and liquid chromatography-mass spectrometry are all traditional pesticide detection methods.These methods have the advantages of high accuracy,precision,and low detection limits,but they also have limitations such as high detection costs and complex steps.As a result,their use in field applications and rapid identification is limited.Fluorescence sensors,which have advantages such as high sensitivity and selectivity,have become one of the most important research objects in the field of sensors:Meanwhile,the method based on the combination of metal organic frameworks（MOFs）and fluorescent sensors can effectively improve the sensitivity and selectivity of the detection system.This thesis utilizes of MOF advantages such as large specific surface area,adjustable pore structure,strong adsorption performance,and fluorescence quenching effect to develop two fluorescence sensing methods for the efficient and sensitive detection of chlorpyrifos and acetamiprid pesticides,thus providing new technologies and methods for pesticide residue detection in food.The research mainly includes:（1）A ratiometric fluorescence strategy with high sensitivity and good anti-interference ability is developed for monitoring chlorpyrifos based on Mn O₂-Au NCs@ZIF-8（MAZIF）.The MAZIF composite integrates the fluorescence property of Au NCs,the protection capacity of ZIF-8 and the function of Mn O₂（quencher and inorganic catalyst）,which enhanced sensing sensitivity via boosting the energy transfer and anti-interference ability by avoiding background effect.The fluorescence emission intensity of Au NCs@ZIF-8 at 635 nm and Mn O₂ catalytic products（2,3-diaminophenazine）at 535 nm can form a typical ratiometric with good anti-interference ability.MAZIF composites can recognize the acetylcholinesterase hydrolysis products（thiocholine）owing to the analyte-initiated reduction of Mn O₂.Combined with the inhibition of organophosphorus pesticides（OPs）on acetylcholinesterase,the ratiometric fluorescence platform is constructed for sensitive detection of chlorpyrifos residues with a detection limit of 0.22 ng m L^-1.The ratiometric fluorescence sensing method is effectively applied for precisely monitoring the residue and degradation of chlorpyrifos in pakchoi,endowing the practical application in food safety monitoring.Simultaneously,the ratiometric fluorescence sensing method was successfully applied to the monitoring of chlorpyrifos degradation in pakchoi,confirming the method’s potential application in food safety monitoring.（2）A fluorescence aptamer sensing method based on zeolitic imidazolate framework-8（ZIF-8）was developed for the highly sensitive and selective detection of acetamiprid.ZIF-8 easily adsorbed 6-carboxyfluorescein-labeled complementary DNA（c DNA-FAM）via electrostatic interaction,hydrogen bonding,and Zn²⁺coordination,and caused a decrease in FAM fluorescence intensity via photoinduced electron transfer（PET）.Metal ions could enhance ZIF-8 adsorption on c DNA-FAM,which was difficult with other nanomaterials,so this adsorption could better resist c DNA-FAM displacement by different sequences and biological ligands.Acetamiprid-binding aptamer（ABA）combined with c DNA-FAM to form double-stranded DNA（ds DNA）that showed weak adsorption on the ZIF-8 surface,resulting in poor PET and high fluorescence of the system.In the presence of acetamiprid,the c DNA-FAM was released from the ds DNA,inducing fluorescence quenching due to the specific interaction between c DNA-FAM and ZIF-8.Compared with ABA-FAM/ZIF-8 sensor,ds DNA/ZIF-8-based aptasensor show better sensitivity for the determination of acetamiprid with a linear range of 0.05-100 ng m L^-1 in agricultural and environmental sample.This work provides fundamental insights into the biointerface science of ZIF-8 with DNA,showing promising applications in biosensor design.