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 (XRPD) analysis, N2-sorption measurements, and
thermogravimetric (TG) 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.