The Construction Of MOFs-based Fluorescence Sensing And Paper-based Electric-field Amplification Device For Glyphosate

Glyphosate is a broad-spectrum and highly effective herbicide commonly used in agriculture for weed control,whose annual global usage is expected to exceed 1,000,000 tons in the coming years.Excessive spraying of glyphosate caused it residue to adsorb in soil particles or leach into surface and groundwater,causing environmental pollution,and eventually accumulating in the human body through the food chain.Therefore,in order to control its residual pollution,there is an urgent need for rapid and simple methods for the determination of glyphosate.Metal-organic frameworks（MOFs）are a class of porous nanomaterials composed of metal ions bound together by organic ligands.Various flexible organic ligands provide MOFs with efficient fluorescence performance.In this thesis,two amino-functionalized MOFs were synthesized,a ratio fluorescence sensing method combined with Rhodamine B was established for glyphosate,and a ratio fluorescent test strip with a fluorescent ring sticker was developed for the rapid visual detection of glyphosate in food and water samples.On this basis,the efficient fluorescent amino-functionalized MOF was combined with electric-field amplification to construct a paper-based analytical device for simultaneous enrichment and determination of glyphosate in soil and water samples.The main research contents and results are as follows:（1）In order to achieve the rapid detection of glyphosate,NH₂-MIL-88（Fe）@Rh B was synthesized,and Cu²⁺was combined as quencher to establish a method based on the ratio fluorescence sensor for the rapid detection of glyphosate.Rh B was incorporated into the MOF,providing a stable fluorescence signal as a built-in reference.Direct fluorescence enhancement caused by hydrogen bond interaction between carboxyl groups from glyphosate and amino groups from NH₂-MIL-88（Fe）@Rh B shortened response time to less than 1 min,and the introduction of Rh B reduced the analysis error caused by the environment and equipment.The method exhibited a linear range of 0.60～45.0μmol/L with limit of detection（LOD）of 0.18μmol/L.Furthermore,glyphosate in four agricultural products（soybean,wheat,cucumber and tea）was quantitatively determined,among which glyphosate was detected in soybean of 5.26μmol/L.（2）In order to further achieve the on-site rapid detection of glyphosate,NH₂-Bi-MOF was synthesized,and combined with Cu²⁺as a quencher to construct a fluorescence sensing system,and based on which,a ratio fluorescent test strip was then designed to establish a visual on-site detection method for glyphosate.With Bi as the central metal,NH₂-Bi-MOF was synthesized with a more efficient fluorescence response to cope with paper-based background interference.A ratio fluorescent test strip has been designed using a ring sticker with a fluorescent signal as a self-calibrating reference to cope with imaging errors.This method provides two analysis modes:visual detection by standard card and gray value quantitative detection through ratio strategy.The method exhibited a LOD of 0.82μmol/L,and the response took only 1 min.Furthermore,glyphosate in soybean,wheat and drinking water was quantitatively determined,among which glyphosate were detected in soybean of 4.40μmol/L.The visual detection results by standard card were also consistent with the quantitative analysis results.（3）To meet the demand for trace target determination,a paper-based electric field amplification device was constructed,and combined with a fluorescent MOF,a paper-based method for online enrichment and fluorescence detection of glyphosate was established.A gourd-shaped paper channel was designed to adjust the electric field strength,and the electroosmotic flow was also controlled to achieve the directional movement and reaction of the target glyphosate and NH₂-Bi-MOF indicator.Compared to conventional test strips without field amplification,the signal intensity was increased by 12500-fold.The method exhibited a linear range of 0.80～200μmol/L with low LOD of 0.20μmol/L.Furthermore,glyphosate in soil and water samples（lake water,tap water,drinking water）was quantitatively determined,among which glyphosate were detected in soil and lake water.