Study And Application Of Organophosphorus Pesticide Sensor By Using Of Nanomaterials Combined With Molecular Spectrum

In this paper,a series of sensors based on nanomaterials combined with colorimetric and fluorescence methods were established for the analysis and detection of pesticide residues in the food and environment.The proposed analytical method exhibited high sensitivity and selectivity for the detection of organophosphorus pesticides（OPs）,and the constructed biosensing platform was cost-effective and easy to operate.The main contents of this paper were summarized as follows:Chapter 1:The background and significance of analytical methods for OPs were introduced in detail,and the common methods for OPs residue detection and the selection of nanomaterials in this paper were discussed.It briefly described the research content of this study and prospected the application of colorimetric and fluorescence methods in the field of OPs residue detection.Chapter 2:A new fluorescence analysis method was proposed to detect parathion-methyl（PM）based on platinum nanoparticles（Pt NPs）and4-amino-3-hydroxy-1-naphthalenesulfonic acid（AHNSA）as fluorescent probe.AHNSA with high fluorescence could combine with Pt NPs by electrostatic attraction,bringing out fluorescence quenching of AHNSA.Acetylthiocholine（ATCh）was hydrolyzed by acetylcholinesterase（ACh E）to produce thiocholine,which could induce the aggrega-tion of Pt NPs by electrostatic attraction and restore the fluorescence intensity of AHNSA.However,in the presence of PM,the catalytic activity of ACh E is inhibited,leading to the quenching of fluorescence of AHNSA again.Under the optimal conditions,the linear range of PM detection was 0.26-53.3ng/m L（R²=0.994）,and the limit of detection was 0.17 ng/m L（S/N=3）.In addition,this method has been successfully used for the determination of PM in food and water samples.Chapter 3:A sensing platform for the rapid quantitative detection of glyphosate with high sensitivity and selectivity was constructed by enzyme-free ratiometric fluorescence and colorimetric dual read-out assay based on ultrathin g-C₃N₄nanosheets（UCN NS）.Fluorescent diaminophenylazine（DAP）with fluorescence was from the oxidation of o-phenylenediamine（OPD）in the presence of Cu²⁺.DAP could inspire a significant fluorescence quenching of nanosheets due to photo-induced electron transfer（PET）,therefore exhibiting a ratiometric fluorescence response.In the presence of glyphosate,the strong chelation of Cu²⁺by glyphosate inhibited the oxidation of OPD,which reduced the fluorescence intensity of DAP,while the fluorescence of the ultrathin nanosheets was restored.Moreover,the oxidation of OPD（colorless）to DAP（yellow）was a distinctly visible color change process,which provides well-suited conditions for colorimetric analysis.At the optimum experimental conditions,the detection concentration range of glyphosate was 0.001-0.48μg/m L,and the limit of fluorometric detection was 0.49 ng/m L（S/N=3）.This assay was simple and easy to use for the detection of glyphosate in food safety and the environment with satisfactory results.Chapter 4:The quantitative analysis of glyphosate has significant implications for the evaluation of food quality and environmental safety risk.First,copper nanoparticles（Cu NPs）were synthesized using cetyltrimethylammonium bromide（CTAB）as a stabilizing agent,which resolved the limitation associated with atmospheric oxidation of Cu NPs with excellent fluorescent stability.Interestingly,the fluorescence of blue-emission CTAB-Cu NPs was quenched by p H-responsive p-nitrophenol（p-NP）via F?rester resonance energy transfer.Herein,a dual read-out sensor based on CTAB-Cu NPs and p-NP was constructed for glyphosate detection for the first time.Specifically,the synthesis of acetic acid（HAc）from acetylcholine chloride（ACh）via hydrolysis catalyzed by ACh E reduces the p H of the mixed solution and prevents the loss of protons from p-NP,which allows fluorescence emission by CTAB-Cu NPs.The presence of glyphosate inhibited the activity of ACh E and the increased p H resulted in proton loss.The fluorescence intensity of CTAB-Cu NPs was quenched and the solution color changed from colorless to yellow with a UV absorption peak at 400 nm.The sensor can detect ultra-trace levels of glyphosate residues with a limit of detection of 5.43 ng/L.The biosensor has been successfully utilized to monitor the degradation of glyphosate in the roots of cabbage and cultivated soil.Chapter 5:Herein,a ratiometric fluorescence and colorimetric sensing platform was constructed based on ZIF/Cu NCs composite nanomaterials and blue carbon dots（b CDs）for highly sensitive and rapid detection of glyphosate by encapsulating copper nanoclusters（Cu NCs）in a metal organic backbone（MOF）.As we know,the competitive complexation of Cu²⁺between the nanoprobe and glyphosate.When different concentrations of glyphosate were present,the ratiometric fluorescence sensor exhibited a unique fluorescence color change from blue to red,while the colorimetric sensing platform exhibited a gradual change from blue to colorless with detection limits of 0.125 ng/m L.What’s more,the constructed sensing platform has been successfully applied to determine glyphosate in actual samples of lake water and cabbage,with the results showing that the dual-signal sensor was reliable and sensitive in practical applications.The outstanding characteristics of this study work were included as follows:（1）The raw materials required for the preparation of nanomaterials are abundant,inexpensive and available,with simple synthesis process and excellent fluorescence stability;（2）the sensing platform constructed based on nanomaterials combined with fluorescence and colorimetric dual reading method can achieve rapid detection of pesticide residues in food and environment with high reliability and selectivity.