pH-sensitive thiamethoxam nanoparticles based on bimodal mesoporous silica for improving insecticidal efficiency

In this study, we synthesized pH-sensitive thiamethoxam-3-(2-aminoethylamino) propyl-bimodal mesoporous silica (P/Thi-NN-BMMs) nanoparticles (NPs). We used this bimodal mesoporous silica (BMMs) mesoporous material as a carrier based on the principle of free radical polymerization. The size of the P/Thi-NN-BMMs NPs was about 891.7 ± 4.9 nm, with a zeta potential of about −25.7 ± 2.5 mV. X-ray powder diffraction analysis, N(2)-sorption measurements and thermogravimetric analysis indicated that thiamethoxam (Thi) was loaded into the pores of the mesoporous structure and that the mesopore surface was coated with polyacrylic acid (PAA). The loading rate of P/Thi-NN-BMMs was about 25.2%. The controlled-release NPs had excellent anti-photolysis performance and storage stability. The NPs showed significant pH sensitivity, and the Thi release rate in pH 10.0 phosphate buffer was higher than those in pH 7.4 and pH 3.0 phosphate buffers. We described the sustained-release curves according to the Weibull model. The relative toxicity of P/Thi-NN-BMMs against peach aphid was 1.44 times that of commercial Thi. This provides a promising instrument for effective insect control and environment protection.