Synthesis Of Intelligent Responsive Slow/controlled Release Pesticide-Fertilizer Based On Polydopamine And Its Synergistic Application

In recent decades,food production increases year after year through massive input of fertilizers and pesticides with minimal expansion of arable land.However,hundreds of millions of tons of fertilizers and pesticides have put enormous pressure on the ecological environment,because traditional pesticides and fertilizers fail to reach the target and crops due to volatilization and loss.This greatly reduces their utilization rate and increases the cost of agricultural production.The application of slow/controlled release technology can effectively solve the problem,which is of vital significance to the construction of sustainable agricultural system.At present,fertilizers and pesticides,as important components of agriculture,have many similarities in slow-release behavior although their functions are quite different.Therefore,it is theoretically feasible to design a sustained release system with dual load and environmental response release characteristics,which can not only improve the utilization rate,but also enhance the stress resistance of crops.In this dissertation,dopamine and silica as the basic raw materials were employed,and two kinds of multi-functional systems were prepared loading pesticide and fertilizer.A variety of testing methods were used to explore their performance.Theie biology tests were carried out,comparing with traditional fertilizer and pesticide release agent,to verify their feasibility for modern green agriculture.The main research contents and results of this dissertation are as follows:1.Mesoporous silica(MSNs)was prepared by sol-gel method with cetyl trimethyl ammonium bromide(CTAB)as a template and ethyl orthosilicate(TEOS)as silicon source.N-trimethoxy methylsilyl propyl-N,N,N-trimethylammonium chloride(50% methanol solution)was used for surface modification.The carrier with adhesion characteristics was obtained by coating polydopamine(PDA)with MSNs by oxidative self-polymerization under the condition of alkalinity.The 2,4-D sodium salt(2,4-D)was loaded into the modified mesoporous silica(MSNs-TA),and trace element zinc was chelated by the active groups of PDA.The slow-release pesticide-fertilizers were prepared with the dual functions of weeding activity and promoting plant growth.The results of release kinetics showed that the release period of 2,4-D and zinc fertilizer was significantly increased.At pH = 7,the release amount of 2,4-D in 144 h was 45.35%,while the release amount of zinc fertilizer in 30 days was only 17.36%.The adhesion experiments of silicon wafers showed that the nanomaterials had strong anti-scour ability after spraying and drying,which may effectively imrove the low utilization rate caused by rainwater scour after spraying.Skin tests showed that the pesticide-fertilizers had better biological safety compared with commercial pesticides.The control experiment of broad-leaved weed showed that the fertilizer and 2,4-D agent had inhibitory effect on purslane and had no apparent ill effect on the germination rate of corn.2.Based on the previous system,hollow mesoporous silica(HMS)was prepared by the hard template method with ethyl orthosilicate as silicon source.1-Tetradecanol(TD)and 2,4-D are loaded into the silica cavity by hollow structure,and coated with polydopamine layer by oxidative self-polymerization,which are used for photothermal transformation,pore sealing and as zinc fertilizer carrier.Zinc acetate was used as zinc source,zinc ions were adsorbed on the surface of polydopamine by chelating,and the pesticide dinotefuran(DF)was coated with dimethylimidazole while ZIF-8 was self-assembled in the outer layer.TD is a kind of phase transition material,which can achieve the solid-liquid transition through temperature regulation to control the release of herbicide.Meanwhile,since ZIF-8 is unstable under acidic conditions,the release rates of DF and zinc fertilizer can be regulated by pH.The loading rates of 2,4-D,zinc fertilizer and DF were 32%,16.8% and 20.1%,respectively.The release data showed that the pesticide-fertilizer had good pesticides loading and release characteristics.The results of potted experiments showed that the pesticide-fertilizer had a significant inhibitory effect on germination of weeds,but had no apparent ill effect on the germination rate of the target crops.The root length and trace element zinc content of corn were also significantly higher than that of the control group,which demonstrated that the pesticide-fertilizer had a significant promoting effect on corn growth.The results of pest control showed that the pesticide-fertilizer could quickly kill all the larvae in a short time and control the larvae quickly at pH<7.0,which was due to the accelerated release of dinotefuran from the dissociation of ZIF-8 under acidic regulation.The combination of herbicide,insecticide and nutrient is expected to show multiple synergistic effects,resulting in cost savings,increased efficiency and increased production.