Synthesis Of Polymer/Metal-Organic Frame(Fe) Composites And Their Applications In Pesticide Controlled Release And Detection

Chemical pesticides are important products in the development of modern agriculture.They are powerful weapons used by people to fight against plant diseases,insects,grass,rats and other harmful organisms.In traditional agriculture,pesticides are often applied in large quantities to ensure the food production.However,only a small part of them could function well,and the rest of them are flowed and remained in the environment,putting a huge burden on the environment and endangering humans and other organisms.In view of the environmental pollution caused by the low utilization rate of pesticides in traditional agriculture,we need to improve the utilization rate of pesticides through new technologies to achieve precise application by reducing application and increasing efficiency.On the other hand,novel technologies need to be integrated to analyze pesticide residues in water,air,soil and food,to ensure that human beings and other organisms are protected from the harm of pesticide pollutants.In this dissertation,we designed and prepared new materials by combining polymers with metal-organic frame materials for controlled release and detection of pesticides,to solve the problem of the low efficiency of pesticides in traditional agriculture.The materials were characterized and their performance were tested by a variety of methods,and their potential practical applications were explored.The main contents and results are as follows:1.Based on the pH responsiveness of MOF,a composite of polydopamine and Fe-MOF（TPDM）was prepared using a simple two-step synthesis strategy for the controlled release of insecticide thiacloprid（THIA）and herbicide 2,4-D Na（2,4-D）to achieve the sustainable pest and weed management.THIA was dispersed evenly in the Tris buffer and then formed polydopamine（PDA）on its surface by oxidative self-polymerization.Then,Fe ions were adsorbed on PDA by double-dentate chelation,and reacted with NH₂BDC to form MIL-101（Fe）.At the same time,2,4-D was encapsulated in situ.Controlled pesticide release was achieved through environmental stimuli.Under alkaline conditions similar to the intestinal microenvironment of pests,the cumulative release of THIA and 2,4-D reached 52.78%and 58.63%after 24 h,respectively.The resistance to UV degradation increased by nearly 4 times and 2times for THIA and 2,4-D,respectively,which was due to the physical barrier effect of the carrier.The composite showed good insecticidal and herbicidal properties,and could effectively remove weeds and control the number of pests.This composite can be prepared by a simple process without organic solvents,and can achieve controlled pesticide release,which will reduce application and increase efficiency of pesticides in practical applications.2.Based on the catalytic oxidation activity of MOF similar to oxidase,a fluorescent biosensor for the detection of organophosphorus pesticides was prepared by the inhibition effect of organophosphorus pesticides on alkaline phosphatase.Then the sensor was combined with sodium alginate hydrogel,and on-site detection of organophosphorus pesticides was realized by using smart phones and chrominance software.Firstly,bimetallic MOF（Fe/Cu）was prepared by one-pot hydrothermal method.Compared with MIL-101（Fe）,MOF（Fe/Cu）showed higher oxidation-like activity,and could catalyze the oxidation of luminol in the absence of H₂O₂to produce oxide luminol with blue fluorescence.As the substrate of alkaline phosphatase（ALP）,L-ascorbate-2-phosphate（AA2P）can be hydrolyzed into ascorbic acid（AA）by ALP,which inhibits the oxidation reaction of luminol and leads to fluorescence quenching,while the addition of organophosphorus pesticides inhibits the activity of ALP and the production of AA,resulting in fluorescence recovery of the mixed solution.Under optimized operating conditions,the fluorescence biosensor had a good linear relationship between fluorescence intensity and logarithmic concentration in the concentration range of 0-2000 nM and 1-1200 nM for Dimethoate and Malathin,and their detection limit was 1.38 nM and 1.25 nM,respectively.A portable sensor was prepared using the fluorescent biosensor and sodium alginate hydrogel,and on-site detection of Dimethoate pesticide was realized with a detection limit of 46.2 nM.This composite portable sensor shows great potential and application value in the detection of organophosphorus pesticides and food safety.