| Pesticides play an irreplaceable role in modern agricultural production, butit always along with the wicked problem of pesticide residue, pollution, low utilization and the toxic side effects.A new formulation,release agent,has become aninterestingresearch direction for its control-released peculiarity. To be specific, Mesoporous materials have been widely used as drug release carriers because of their unique pore size, high specific surface area and pore volume. Compared to disordered macro-mesoporous silica, mesoporous silica has a higher drug loading capacity and a better slow-release performance. What’s more, the ektexine of the mesoporous silica can prevent pesticides from the sun ultraviolet photolysis. However, the research about the effects of mesoporous silica on plant growth and penetration performance of silica on plant leaves were still rare.Thus this thesis was aimed to find put these questions and make sure thatmesoporous silicacan be used as a new slow-release pesticide carrier in the practical application of leaf penetration.In our research, mesoporous silica was firstly preparedvia the template method and we also evaluated the preparation process usingsingle factor experiment. Then the effects of nanosilicon dioxide of threedifferent particle sizes on the cowpea leaves penetration and cowpea growing was observed. Finally theloading capacity of nanosilicon dioxideand drug dispersing performanceon cowpea leaves were studied.The results showed that the factors of alcohol-water ratio, the amount of TEOS and the amount of sodium hydroxide great influenced the particle size of silicon dioxide. In details, as the alcohol-water ratio decreases, the particle size decreases; while the particle size will broaden through increasing the amount of TEOS and sodium hydroxide.And stirring rate has nothing to do with the particle size.At the same time, we prepared three different particle size of silica based on three different alcohol-water ratios and the samples were characterizedby using three instruments including laser particle size analyzer, scanning electron microscope(SEM) and Fourier Transform InfraRed(FTIR).According to the results of laser particle size analyzer and(SEM), all the nanoparticle shape of three different size is a smooth and regular sphere and particle size are120 nm and 100 nm and 40 nm,respectively. Also the results of FTIR chromatogram showed that a strong absorption peakwas observed under the wavelengthof 801.74cm-1, 476.04cm-1 and 967.53cm-1, whichdemonstrated that these samples belong to nanosilicadioxide. Furthermore, the result of nitrogen adsorption specific surface area and pore size analyzer showed that the specific surface area are in the range of242.558m2/gand352.391m2/g among three particle size. The larger specific surface areaproved that the prepared samples are belong to silica hollow spheres.In order to testify the safety of the nano-silica to cowpea, the experiment applied nano silica suspension through two parts of cowpea leaves and roots, and the plant height and fresh weight of cowpea seedlings were observed. The results showed that nano-silica particles had not significantly effect on cowpea seedlings which showed that the silica nanospheres were safety on the plants, and can be used as the environmental friendly pesticide carriers.Based on three different particle diameter silica fluorescent surface modification, the observation of fluorescence microscopy and laser scanning confocal microscope was constructed. The results showed that 40 nm and100 nmparticle diameter silicas can penetrate the cowpea leaves entering into the body of the cowpea,while 120 nm particle was mostly found in the blade surface aggregation. With the increase of particle size, the aggregation of particles on the surface of the leaves increased, and the ability of large particles of silica to penetrate the leaves was decreases. The capability of different particle sizes of nano silicon dioxide to penetrate the leaves of cowpea was different.Studies on the loading efficiency of pesticides in nano-silica showed that the loading efficiency of abamectin in nano-silicais was 28.21% for 40 nmparticles, 33.56% for 100 nm particles and 33.35% for 120 nm particles, respectively. The contact angle measurement results showed that the contact angles were all less than 90°; the contact angle of 40 nm silica particleswas was in range of 52-54°, 100 nm silica particleswith 51-55°, 40 nm silica particleswith 57-60°. The contact angleresults also showed that silica suspension can better wetting the cowpea leaves.Thus the nano silicon dioxide can be used as a good pesticide carrier. |
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