DOI: 10.5061/dryad.79cnp5ht5
title: pH-sensitive thiamethoxam nanoparticles based on bimodal mesoporous silica for improving insecticidal efficiency

description: 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.
description: Particle size distributions of BMMs, NN-BMMs, P/NN-BMMs and
 P/Thi-NN-BMMs were displayed in Fig. 3. We determined particle size,
 polymer dispersity index (PDI), and zeta potential of BMMs, NN-BMMs,
 P/NN-BMMs,and P/Thi-NN-BMMs according to dynamic light scattering (DLS)
 using the Zetasizer Nano ZS (Malvern Instruments Ltd., Malvern,
 UK). XRPD patterns, TG curves,
 N<sub>2</sub> adsorption/desorption isotherms, and BET surface
 areas and pore volumes of P/Thi-NN-BMMs and the control samples were
 displayed in Fig 4. We performed X-ray powder diffraction on an X-ray
 powder diffractometer (D8 ADVANCE X, Bruker/AXS, Karlsruhe, Germany) using
 nickel-filtered Cu Kα radiation (λ = 0.154 nm). The tube voltage and tube
 current were 35 kV and 35 mA, respectively, and the scan speed was 0.5
 min<sup>-1  </sup>(Fig 4A). We conducted TG analysis using a
 thermal analyzer (PerkinElmer, Waltham, MA, USA), under the following
 conditions: nitrogen atmosphere, a flow rate of 20
 mLmin<sup>-1</sup>, and a heating rate of 10 °C
 min<sup>-1</sup>; the highest temperature was 800 °C. The
 pesticide loading content of the P/Thi-NN-BMMs nano-pesticide was
 calculated according to the TG curve(Fig 4B). We obtained nitrogen
 adsorption-desorption isotherms on an Autosorb-iQ pore analyzer
 (Quantachrome, Boynton Beach, FL, USA) at 77 K under continuous adsorption
 conditions. Brunauer-Emmett-Teller (BET) and used Barrett-Joyner-Halenda
 analyses to calculate the surface area, pore size, and pore volume(Fig 4C,
 4D). Photodegradation curves of
 P/Thi-NN-BMMs Nps and technical Thi under UV irradiation were displayed in
 Fig. 5. We tested the photolytic properties of P/Thi-NN-BMMs
 NPs with technical Thi as the control. The samples were divided equally
 into culture dishes and irradiated under a UV lamp (500 W) at a distance
 of 20 cm in a UV-light incubator (WFH-203B, Shanghai Precision Instrument
 Co., Ltd., Shanghai, China). At a given irradiation time (12, 24, 36, 48,
 60, 72, and 96 h), we separately collected the culture dishes and analyzed
 the Thi contents in the samples by high-performance liquid chromatography
 (HPLC). A gradient of methanol–water(40:60) was programmed over 30 min at
 a flow rate of 1 mL min<sup>-1</sup> with detection at 240 nm.
 We performed all experiments in triplicate. Stability of P/Thi-NN-BMMs NPs at
 different storage temperatures after 14 days were displayed in Fig. 6. We
 determined the stability of the P/Thi-NN-BMMs NPs according to CIPAC MT 46
 (Miscellaneous Techniques and Impurities: MT 46 Accelerated Storage
 Procedure, Collaborative International Pesticides Analytical Council) and
 GB/T 19136–2003 (Determination of Heat Storage Stability of Pesticides,
 Chinese National Standard). We stored the samples at 4 ± 2 °C and 25 ± 2
 °C for 7 d and 54 ± 2 °C for 14 d, and analyzed the Thi content using
 HPLC. Cumulative
 release profiles of P/Thi-NN-BMMs with pH of 3.0, 7.4, and
 10.0 were displayed in Fig. 7. we suspended 30 mg of
 P/Thi-NN-BMMs  in 100 mL of an ethanol:water mixture (30:70, v/v), which
 was used as the release medium. Then, we collected 2 mL of the sample for
 testing at fixed time intervals, and the system was replenished with an
 equal amount of fresh medium. We measured Thi concentrations using HPLC
 and calculated the release rate of Thi from the nano-delivery sample. The
 liquid-phase detection conditions included a mobile phase of
 methanol:water (volume ratio 40:60), injection volume of 10 μL, wavelength
 of 240 nm, and retention time of 4 min.
description: Someone can use this dataset directly, and there are no missing
 values.