Magnetic core–shell nanoparticles coated with a molecularly imprinted organogel for organophosphate hydrolysis

Catalytic core–shell nanoparticles were obtained by coating an iron oxide core with a hybrid organic–inorganic silica shell using vinyl-triethoxy-silane and amino-propyl-triethoxy-silane. The amino group was further functionalised with arginine, used as catalytic moiety for the inactivation of organophosphate pesticides through hydrolysis. By exploiting the vinyl groups of the organosilica as anchorage, an additional outer layer made by molecularly imprinted organogel was built up through high-dilution radical polymerisation. The resulting organogel contains the imprinting complex, which derives from the guanidinium groups of the arginine and the organophosphate used as molecular template. The removal of the organophosphate from the imprinted cavities allowed obtaining core–shell magnetic nanoparticles with a molecularly imprinted acrylamide-based outer layer. These nanoparticles are capable of hydrolysing the commercial pesticide Paraoxon with a reaction rate 50 % faster than the corresponding background hydrolysis.