magnetite, oximate ion, catalysis, nerve agent decomposition
Organophosphorus pesticides and warfare agents are not readily hydrolyzed in aqueous media without applying extremes of pH, heat, or bleach. We show that suspensions of magnetite (Fe3O4) nanoparticles modified with a common antidote, 2-pralidoxime (PAM), its polymeric analog, poly(4-vinylpyridine-N-phenacyloxime-co-acrylic acid), or poly(N-vinylimidazole-co-acrolein oxime-co-acrylic acid) (PImAA) catalyze the hydrolysis of organophosphate (OP) compounds such as diisopropyl fluorophosphate (DFP) or insecticide diethyl-p-nitrophenyl phosphate (paraoxon) serving as models of the warfare nerve agents, at neutral pH. The oxime-modified magnetite particle serves as a nano-sized particulate carrier with a powerful a-nucleophile, the oximate group, immobilized on its surface. The rates of OP hydrolysis by the PAM- or PImAA-modified magnetite are comparable to those of the most potent copper-based catalysts. The oxime-modified magnetite nanoparticles are colloidally stable at neutral pH and are readily recovered for reuse from the aqueous milieu by high-gradient magnetic separation methods with no loss of catalytic activity.