Synthesis, characterization, and partial risk assessment of dimethoate nanoformulations prepared using acrylic acid/polyethylene glycol copolymers and zinc oxide nanoparticles

Abstract

comparative field-scale evaluations linking nanoformulation efficacy, residue dissipation, and soil microbial safety remain limited. This study aims to develop and evaluate novel nanoformulations of dimethoate using biodegradable acrylic acid/ polyethylene glycol (AA–PEG) copolymers, with and without zinc oxide nanoparticles (ZnO-NPs), to enhance efficacy while reducing environmental impact. The nanoformulations (NP-Di and NP-Di/ZnO) were synthesized, characterized, and evaluated in terms of loading efficiency, release kinetics, bio-efficacy, environmental safety, and residue dynamics. Loading efficiency ranged from 59% to 72% across pH levels (5–9), with NP-Di/ZnO exhibiting the most sustained release profile. In field trials against Bemisia tabaci and Thrips tabaci on soybean, both nanoformulations applied at 400 mg/L showed significantly higher and more persistent insecticidal efficacy than the commercial emulsifiable concentrate (EC). Eco-toxicological assessment demonstrated that AA–PEG copolymers and ZnO nanoparticles alone did not adversely affect soil microorganisms, even at elevated concentrations. Although all dimethoate formulations reduced microbial growth, the nanoformulations exhibited a plateau effect at higher concentrations (400–800 mg/L), whereas the commercial EC caused progressively greater inhibition. Residue analysis revealed faster dissipation of dimethoate from nanoformulations on soybean leaves and pods (DT50: 0.39–1.86 days) compared to the EC (DT50: 1.92 days), indicating reduced environmental persistence. Overall, the combination of enhanced bio-efficacy and lower residues reflects a more favorable balance between pest control performance and environmental safety. These findings highlight AA–PEG/ZnObased nanoformulations as promising, eco-friendly candidates for the sustainable management of sucking pests