Study On The Construction Of Imidacloprid Micron And Nanometer Delivery Systems And Their Deposition And Translocation On Cucumber

Pesticides,a kind of chemical substance,are used to prevent and control crop diseases and pests,improving food production and safety.Most pesticide compounds are insoluble in water,and the traditional pesticide formulations have the problems of large particles,poor dispersion,low effective utilization rate and large dosage,which have led resources waste and caused serious damage to the ecological environment.It is an important scientific approach to overcome the functional defects of traditional formulations and improve the bioavailability of pesticides to construct pesticide nanoformulations,based on the characteristics of small size effect,interface effect and high permeability effect of nanomaterials.In recent years,more and more attention has been paid to the research of the constructions of nanopesticides and the evaluation of biological activity.However,there are relatively few studies on the wetting,deposition and transport of nanopesticides on plants.The study on the deposition and translocation of pesticide nanoparticles on plants is helpful to clarify the interaction between nanopesticides and plants,which can lay a theoretical foundation for the optimization design of efficient and green nanometer delivery system.In this paper,imidacloprid nanorods were constructed by wet media grinding combined with orthogonal experimental design,and further were compared with commercial formulation.The preparation process,morphology,particle size distribution,crystal structure,wettability,stability and other aspects were characterized and evaluated.Furthermore,the physicochemical properties of imidacloprid micron and nanometer systems at different concentrations and the differences in wetting behavior on leaves were compared.Based on the nanometer effect,the rainfastness behavior before and after washing and the translocation behavior of imidacloprid micro and nanometer systems were studied.1.Imidacloprid nanorods were prepared by medium grinding method combined with orthogonal experiment.The imidacloprid nanoformulations showed rod-like structure.The average sizes of short and long axis were 289 nm and 600 nm,respectively.The Zeta potential was-39.3 m V.The XRD crystal structure showed that imidacloprid nanorods had obvious crystal characteristic peaks and good stability.The storage stability test showed that imidacloprid nanorods had good stability after cold storage and heat storage.Compared with commercial water dispersible granules,the surface tension of imidacloprid nanorods was significantly lower than that of the other two commercial formulations.The contact angles of imidacloprid nanorods on the cucumber,hydrophobic parafilm and cabbage leaves,respectively were significantly lower than those of the other two commercial formulations.Meanwhile,the retention of imidacloprid nanorods was higher than that of commercial water dispersions,indicating that the wetting and retention properties of imidacloprid nanorods were significantly improved.2.The physicochemical properties and wetting behaviors of imidacloprid micron and nanometer systems at different concentrations were compared.Specifically,the morphology,crystal structure,surface tension,wettability and biological activity of the two imidacloprid delivery systems were compared and evaluated.In terms of morphology characterization,the particle size of imidacloprid micron delivery system were micro-scale when the concentration was 0.3% and 0.1%,while the particle size of the imidacloprid nanometer system had growth as the concentrations changed.The nanometer delivery system was short-like rod at the concentration of 0.3%,whereas in long rod structure at 0.1%.However,when the concentration was 0.05%,no particles was seen under electron microscope whether micron or nanometer system.In the aspect of crystal structure,imidacloprid micron system were more consistent with the crystal structure of the active ingredient,while the peak shape of imidacloprid nanometer system had a little change.In terms of surface tension and contact angles on parafilm and cabbage leaf,imidacloprid nanometer delivery system were significantly smaller than that of micron system.In terms of biological activity,the toxicity of imidacloprid nanometer system was 1.3 times that of micron system.In general,imidacloprid nanometer system had better foliar wettability and bioactivity than micron system.3.The rainfastness characteristics of imidacloprid micron and nanometer system was discussed.The qualitative morphology observation shows that a large number of imidacloprid rodlike structures remained on the cucumber leaves after washing,while most of the micron particles were washed off.The quantitative test results showed that the deposition rate of imidacloprid nanometer system was 24%,while the imidacloprid micron system was 31%.The content of imidacloprid nanometer system was slightly higher than that of micron system.In the study on the translocation of imidacloprid micron and nanometer system in cucumber plants,both of the content of imidacloprid in the treated leaves treated by imidacloprid micron and nanometer delivery system reached the maximum on the 7th day.In the nanometer delivery system,the pesticide content in the upper and lower leaves of treated leaves showed a trend of increasing first and then decreasing,while the content of imidacloprid in the upper and lower leaves showed certain fluctuation with different days.The contents of pesticides translocated into the upper and lower leaves were significantly lower than that of treated leaves,that is,most of the pesticides remained on treated leaves.