Preparation Of Mesoporous Silica Nanoparticles And Their Insecticidal Effect On Three Grain Storage Pests After Loading With Biopesticides

Mesoporous silica nanoparticles(MSN)can not only be used as nanoparticles with a direct insecticidal effect on grain storage pests,but also have the advantages of large specific surface area,high pore capacity and good biocompatibility,making them ideal carriers for loading pesticides.Methoprene(Met)and allicin(Alli)have good control effects on grain storage pests,but the shortcomings such as easy oxidative degradation,expensive cost and poor water solubility limit their application and development in grain storage pest control.In this study,the preparation method of MSN was investigated and optimized by template method;the lethal effect of MSN with different particle sizes and doses on three grain storage pests was investigated;subsequently,MSN loaded with alliin and allicin and their performance were investigated,and the insecticidal effect and biological activity of the two types of nanoparticles were measured using Tribolium castaneum(Herbst)larvae and three grain storage pests as test pests,respectively.The insecticidal effects and bioactivity of the two nanoparticles were determined.The results showed that:Under the condition of deionized water,the three factors of methanol,ethyl orthosilicate(TEOS)and sodium hydroxide(Na OH)solution had significant effects on the particle size of the prepared MSN.Under the premise that the particle size distribution index(PDI)was less than 0.7,the particle size of the prepared MSN was influenced by the amount of methanol,and the particle size decreased with the decrease of methanol;the increase of the amount of TEOS and Na OH both increased the particle size of MSN;the particle size of the prepared MSN was not influenced by the amount of Hexadecyl trimethyl ammonium bromide(CTAB),but it would affect the particle size distribution of MSN.By comparing the particle size of MSN,the best conditions for the preparation of MSN were selected as 8 m L of methanol,0.5m L of TEOS,0.1 m L of Na OH solution and 0.3 g of CTAB.The MSN prepared under these conditions had a regular spherical shape with a smooth surface and a particle size of about 40nm;the particles were well dispersed with a normal and concentrated particle size distribution;the particles had a good mesoporous structure.With reference to the recommended dosage of diatomaceous earth in the national standard,the MSN was bioassayed by the grain mixing method with the test insects of T.castaneum,Sitophilus oryzae(Linnaeus)and Rhyzopertha dominica(Coleoptera)were effective in controlling all three grain storage pests.The smaller the particle size,the better the control effect of MSN on T.castaneum,S.oryzae and R.dominica at the same dose,the mortality rate of T.castaneum,S.oryzae and R.dominica treated with 147 nm at the 14th day was 62.22%,86.67%and 36.67,respectively;the higher the dose of MSN,the better the control effect,at the same particle size(147 nm),the mortality rate of T.castaneum,S.oryzae and R.dominica treated with 1.2 g/kg The mortality rates of T.castaneum,S.oryzae and R.dominica at the14th day were:94.44%,100%and 72%,respectively.Mesoporous and Alliin were loaded onto MSN modified with silane coupling agent 3-aminopropyltriethoxysilane(APTES)to prepare drug-loaded nanoparticles.The modified MSN and MSN loaded with two pesticides were characterized,and the results showed that the particle size of MSN-APTES was about 45 nm,Met@MSN-APTES and Alli@MSN-APTES were about 50 nm,and the three particles were well dispersed with concentrated particle size distribution;the specific surface area of Met@MSN-APTES was 268.948 m~2/g,with a pore volume of 1.22 cm~3/g and a pore diameter of 0.638 nm and the specific surface area of Alli@MSN-APTES was 188.8873 m~2/g,with a pore volume of 1.11 cm~3/g and a pore diameter of 0.871 nm,proving that both allylene and alliin are present in the surface and mesoporous structures of MSN,and by the analysis of the FTTR results,the The physicochemical properties of the loaded enamectin and allicin were not changed,and the loading rate was 62.1%and 51.2%,respectively,and the good slow-release effect for enamectin and allicin at different p H values,with the release rate of about 60%and 55%at 72h,respectively.The insecticidal activity of Met@MSN-APTES and Alli@MSN-APTES was investigated using T.castaneum larvae as the test insects of Met@MSN-APTES and adults of three grain storage pests,T.castaneum,S.oryzae and R.dominica,as the test insects of Alli@MSN-APTES.The results of Met@MSN-APTES related experiments show that:Met@MSN-APTES had the highest insecticidal effect on T.castaneum larvae with 63.33%mortality at 14 days of treatment at a dose of 10 mg/kg,which was significantly higher than the insecticidal effect of 35.33%for Methoprene and 33.33%for MSN(P<0.05).Compared with Alliin,the fumigant and touch-killing effects of Alli@MSN-APTES on T.castaneum,S.oryzae and R.dominica decreased with increasing release time.At a fumigation dose of 32μg/L,the fumigation mortality rates were 93.33%,66.67%and 80.00%for T.castaneum,S.oryzae and R.dominica,respectively,after 24 h of release;and at a touch kill dose of 208μg/cm2,the touch kill mortality rates were 96.67%,95.56%and 96.67%for T.castaneum,S.oryzae and R.dominica,respectively,after 24 h of release.In summary,the MSN prepared in this thesis has good morphology,good specific surface area and pore capacity,and is effective against T.castaneum,S.oryzae and R.dominica;MSN has high loading rate and good slow release performance for two biopesticides,Methoprene and Allicin,and can improve the insecticidal effect of biopesticides,which can provide theoretical basis and application reference for the integrated control of grain storage pests and the development of new scientific grain storage and green grain storage.