Preparation And Application Of Light-responsive Controlled-Release Pesticides

Pesticides play a key role in improving the quality and yield of agricultural products in agricultural production.However,traditional pesticides are easily affected by environmental factors during the spraying process,causing it to be lost to the atmosphere,water,and soil environments through volatilization,runoff and degradation,which not only cause agricultural non-point source pollution,but also endanger human health by the cumulative effect of the food chain.Therefore,this paper is based on the research and development of new pesticide formulations,which can regulate the release of pesticide active ingredients in carriers according to external environmental stimuli,avoiding premature pesticides leakage and improving the utilization efficiency.Among them,light-responsive controlled-release pesticides are widely accepted because of their convenient operation and less negative impact on the environment and plants.This work not only provides a solution for successful implementation of the "double reduction" project,but also has important reference value for the sustainable development of green agriculture.The results of this paper include the following parts:(1)A controlled release glyphosate granule pesticide(ONCHP)was successfully prepared by wet granulation and coating process using biochar,attapulgite,glyphosate,amino silicone oil,ethyl cellulose and NH4HCO3 as raw materials.The effect of ingredient ratio on the release of pesticides from the granules was studied to obtian optimal preparation conditions.We also studied the effects of pH and different coexisting ions on their release.At the same time,we focused on the mechanism of the release of the granule pesticide in response to infrared light.Through the morphology analysis,the determination of the photothermal conversion efficiency of the biochar,and the study of the release kinetics,we found when the granule pesticide was excited by infrared light,due to the photothermal effect of biochar,the temperature of the system rises rapidly,which causes the decomposition of NH4HCO3 to generate a large amount of CO2 and NH3.It would destroy the composite membrane on the surface of ONCHP by forming a large number of pores,thereby promoting the release of glyphosate from ONCHP.Therefore,the pesticide preparation has excellent infrared light controlled release performance,and the control effect on weeds is also more significant than glyphosate alone,and the prepared materials have a wide range of sources from nature,which makes this technology have potential application prospects.(2)Using CaCO3 synthesized by co-precipitation method as template and dopamine hydrochloride as C source,hollow carbon microspheres(HCM)were prepared by template etching as pesticide carriers,and then HCM was modified by polyethylene glycol and α-cyclodextrin successively.The two formed a gel coated on the surface of HCM through host-guest inclusion,thereby preparing a controlled-release imidacloprid with infrared light response.The experimental results show that the encapsulation of polyethylene glycol/α-cyclodextrin gel can effectively inhibit the leakage of imidacloprid,and it has good heat-sensitive properties,which plays a key role in the controlled release performance of nano-pesticide.This is because HCM has excellent photothermal conversion performance for infrared light.When the temperature of the system increases to the gel-sol transition temperature of polyethylene glycol/αcyclodextrin,α-cyclodextrin will slips out from polyethylene glycol chain,resulting in a gel-to-sol phase transition,which would facilitate the release of imidacloprid.Therefore,this work provides a potential solution for reducing the loss of pesticides and improving the utilization efficiency of pesticides,showing a broad application prospect.(3)Chitosan was successfully modified with the photosensitive molecule 2nitrobenzaldehyde by Schiff base reaction,and then a chitosan-based UV lightcontrolled smart pH-responsive pesticide was prepared by further physicochemical modification.We systematically studied the formation mechanism of 2nitrobenzaldehyde/chitosan and its photolysis reaction by 1H NMR spectrum,FTIR and UV-Vis absorption spectroscopy,laying a solid foundation for studying the mechanism of the pesticide release in response to ultraviolet light.In addition,the method of in situ photoacid generation proposed in this work can not only precisely regulate the release of pesticides,but also avoid the problem that the traditional chitosan-based pesticide controlled release system must rely on an external acid solution,which may cause environmental pollution.At the same time,the controlled-release pesticide can also be combined with the existing black light trapping technology to realize the functions of attracting and killing insects.Thus,it is expected to control insect pests more efficiently,economically and safely,displaying great significance for reducing dose and increasing efficiency of pesticides and promoting the sustainable development of green agriculture.