Preparation And Adhesion Properties Of Silica Based Nanopesticide System

Pesticides play an important role in preventing major biological disasters and ensuring the increase and stability of national grain production.However,traditional pesticide preparations still have some disadvantages such as poor dispersibility,dust drift,large use of organic solvents and low effective utilization rate.In the actual application process,the loss ratio of pesticide is high and the loss of pesticide droplet causes different degrees of pollution to the surrounding environment.Therefore,it is a good solution to reduce the loss of pesticides during the application process by increasing the adhesion rate and deposition amount of the active ingredients of the pesticides on the target foliage.In this paper,starting from the perspective of improving the wetting effect and adhesion ability of nanopesticides on the target foliage,using mesoporous silica as the substrate material for shape design,and modification of affinity chemical substances,and the basic research of nanopesticide system with high adhesion was carried out.The effects of the morphology of the carrier and its surface modifiers on the wettability and adhesion of the nanopesticide system were studied in detail and the anti-photolysis ability and response release capacity were also evaluated.The specific research results are as follows:(1)Preparation of Janus hollow mesoporous silica nanospheres and construction of pH-responsive release systemHollow mesoporous silica nanospheres(HMS)were synthesized by sol-gel and selective etching.The average diameter of the HMS was 350 nm,and the thickness of the shell was about 50 nm.Then,the Janus hollow mesoporous silica nanospheres(J-HMS)with amphiphilic surface were prepared by the paraffin shielding method.Using Janus hollow mesoporous silica nanospheres as the carrier to load abamectin(the drug loading efficiency is 12%),the abamectin/Janus nanopesticide loading system(Aba@J-HMS)was constructed.The wetting and adhesion properties of J-HMS carriers on hydrophobic leaves and hydrophilic leaves were studied by using the contact angle and the retention amount of suspension as evaluation indexes,respectively.The results showed that Aba@J-HMS system showed better wetting and adhesion properties on both hydrophilic and hydrophobic leaves.The Aba@J-HMS system showed good photostability and pH-responsive stimulus release characteristics.(2)Preparation of cap-like mesoporous silica nanocarriers and construction of NIR/pH-responsive release systemCap-like mesoporous silica nanocarriers were synthesized by sol-gel method in a solution containing n-amyl alcohol.The carrier has a diameter of 300 nm,a thickness of 80 nm,the center is concave,and there is an obvious mesoporous structure,and a large specific surface area(728.7 m~2/g).After the surface modification of amino group,the carrier is loaded with dinotefuran(the drug loading efficiency is 24.7%),and polydopamine were introduced to block pesticides through dopamine self-polymerization.The nano-pesticide system has the ability to release the drug in response to NIR/pH stimulation.The cap-like structure is conducive to deposition on the leaf surface,and the polydopamine modification layer is conducive to the foliar adhesion of the carrier.The synergistic effect of the two makes the nanopesticide system have excellent wetting and adhesion properties,and the retention amount of samples on the leaves of cucumber and cabbage reaches 35.3 mg/cm~2 and 15.2 mg/cm~2,respectively,and the adhesion rates reached 80.1%and 71.9%,respectively.In addition,the nanopesticide system showed excellent photostability under UV irradiation.(3)Preparation of mesoporous silica nanosheets and construction of redox/pH-responsive release systemMesoporous silica nanosheets(H-MSN)were synthesized by double template method.The nanosheets had obvious hexagonal flat structure,with a specific surface area of 759.9 m~2/g,a transverse diameter of about 340 nm,a thickness of about 80 nm,as well as regular channels being perpendicular to the plane.The surface of H-MSN was coated with polyethylene glycol diacrylate methyl ester(PEGDA)and sulfhydryl modified polyethylene imine(PEI-SH).The introduction of hydrophilic polymer chain PEI-SH/PEGDA improved the leaf wettability and adhesion ability of H-MSN,and the retention amount of IMI@H-MSN@PEI-SH/PEGDA on cucumber and cabbage leaves was up to 46.0 mg/cm~2 and 19.0 mg/cm~2,respectively.The adhesion rates on the leaves of cucumber and cabbage by fluorescence imaging method were 87.9%and 82.4%respectively,which were consistent with those measured by the UV absorption method.The system can realize the response release of drugs under redox/pH conditions and has good photolysis resistance.