Preparation Of Prothioconazole Nanoparticles And Their Absorption,Migration And Distribution In Soybean Plants

The amount of prothioconazole is increasing year by year,and improving the utilization rate of pesticides is the basis for reducing pesticide residues and ensuring environmental safety.Using nanomaterials as a carrier to load pesticides,controlling the slow release of pesticides,and making them continuously and effectively act on the target for a long time is an effective way to improve the utilization rate.In this paper,carbon quantum dot-modified prothioconazole drug-loaded nanoparticles(Pro@FL-MSNs)were prepared by sol-gel method and high temperature calcination.The release efficiency of nanoparticles was studied by the dialysis bag method.The growth rate method was employed to study the biological activity of Pro@FL-MSNs.The absorption,migration and distribution behavior of Pro@FL-MSNs in soybean plants were investigated by fluorescence microscopy combined with UPLC-MS/MS.The purpose of this study is to improve the persistence period of prothioconazole,reduce its use risk,and provide theoretical and technical guidance for pesticide reduction.The main research results are as follows:1.It was observed by scanning electron microscope and transmission electron microscope that the prepared nano-silica exhibits monodisperse spherical shape and highly ordered mesoporous structure.After loading prothioconazole,the surface of the nanoparticles became relatively smooth and the mesoporous structure tended to disappear.2.When the mass ratio of carrier material to pesticide was 4:3,the loading reached the maximum,which was 28.09 ± 2.15 %.Pro@FL-MSNs have sustained release properties,and the release mechanism is diffusion and erosion,while the release of prothioconazole technical drug is mainly diffusion.Pro@FL-MSNs have excellent fluorescence properties and have different emission wavelengths under different excitation wavelengths.3.When the concentration of active components was 20 mg/L,the antibacterial activities of Pro@FL-MSNs against Fusarium graminearum schw,Phomopsis longicolla Hobbs,Fusarium solani and Phytophthora sojae were 91.25%,82.50%,84.61% and 40.91%,respectively,which were superior to that of prothioconazole technical(72.95%,77.50%,65.52% and 32.58%).4.Based on Qu ECh ERS pretreatment method combined with UPLC-MS/MS,a residue analysis method of prothioconazole and its metabolite prothioconazole-desthio in soybean plants was established.The addition recovery(72.26-94.56%)and relative standard deviation(1.50-12.55%)of each sample were within the allowable range,indicating that the method had good accuracy and stability.The limit of quantification(LOQ)of the method was 0.05 mg/kg.5.Under root application,Pro@FL-MSNs adsorbed or aggregated on the outer epidermis of roots by electrostatic force,then diffused into root cells through pore size,and then transported to stems and leaves above ground through xylem vessels with transpiration pulling force.Under foliar spray,Pro@FL-MSNs deposited on leaves and then diffused into the cuticle or penetrated into leaf tissue through stomata,and then transported down long distances through the sieve tube of the phloem.6.Compared with 30% prothioconazole dispersible oil suspension,the degradation rate of prothioconazole in Pro@FL-MSNs was slower,which could make it produce fewer degradation products on soybean plants.In addition,after treatment with 30%prothioconazole dispersible oil suspension for 10 days,the residual amount of prothioconazole in soybean tissues was lower than the limit of quantification(LOQ = 0.05mg/kg)of the method and was not detected.However,after 14 days of Pro@FL-MSNs treatment,the residues of prothioconazole were not detected in all soybean tissues,which was far lower than the national maximum residue limit(1 mg/kg)of prothioconazole in soybeans,and the use risk was low,which helped to improve the persistent period of prothioconazole and reduce the application dose,thereby reducing environmental pollution.