Preparation And Efficacy Of Self-assembled Mesoporous Silica Slow/Controlled Release Fungicide

Pesticides are considered to be the most effective way to prevent and control pests and plant diseases,ensure food production,and increase grain output agriculture.However,traditional pesticides are currently the mainstay in our country at present.Due to their poor water dispersibility,poor stability,floating dust,volatilization,and loss,they cannot fully act on targets and crops,resulting in the reduction in the effective utilization of pesticides.With the gradual rise of nanotechnology in agriculture,the slow/controlled release pesticides have developed rapidly.The development of pesticides responsive to environmental stimuli has significant advantages in improving the utilization of pesticides and reducing environmental pollution,which is of great significance to the construction of a sustainable agricultural system.To simplify the preparation process of nanomedicine and improve the affinity of pesticide targeting,the fungicides boscalid（Boscalid,Bos）and hexaconazole（Hexaconazole,HEX）were used as model drugs.Based on Bimodal Mesoporous Silicas（BMMs）,sustained-release and light-responsive nano-pesticides were successfully constructed,and their characterization properties and biological activities were tested respectively.This research provides new ideas and theoretical basis for the development of high-efficiency pesticide reagents.The main work are as follows:1.Using the fungicide Bos as the research object,nanopesticides were prepared using one-step and two-step methods based on BMMs.The one-step process was to assemble pesticide molecules,Cetyltrimethyl ammonium bromide（CTAB）and Tetraethyl orthosilicate（TEOS）into silicon dioxide nanospheres（SNSs）simultaneously through a rapid stirring,and then the nano-drug Bos@SNS/t was obtained.The two-step method was also called the solution adsorption method.To prepare the nanopesticide Bos@BMMs,Bos was directly loaded into the pores of BMMs through physical adsorption.The nanopesticides prepared by the two methods are spherical in shape,uniform Ly distributed,and nano-sized in size,with particle sizes of 377.4±3.2nm（Bos@SNS/t）and 323.9±2.9 nm（Bos@BMMs）,respectively.Adhesion ability and thermal stability are significantly improved.The two carriers,SNSs and BMMs,could significantly prolong the sustained-release period of boscalid and accelerate the release of pesticide molecules in alkaline conditions.The antibacterial effects of the two nano-scale sustained-release pesticides were better than those of the original pesticide with the same content.Compared with the two-step method,the one-step method greatly simplifies the traditional complicated preparation method,shortens the time of synthesis and preparation,and improves the preparation efficiency.2.The BMMs carrier was prepared by the sol-gel method.The paminoazobenzene（Azo）was modified and grafted with BMMs,and then the fungicide hexaconazole（HEX）was loaded into the silica pores due to the mesoporous structure characteristics.A strong host-guest complex was formed between the trans m Azo andβ-CD and were used to control drug release from BMMs.The particle of nanopesticide was regular spherical shape.The hydrated particle size was 387.2 nm and the drug loading rate was 27.3%.It is expected to realize the purpose of controlled release of the pesticides and reduction of the number of sprays.