Reactive Silver and Cobalt Nanoparticles Modified with Fatty Acid Ligands Functionalized by Imidazole Derivatives

Novel nucleophilic ligands were synthesized from oleic acid conjugated with 2-mercaptoimidazole via a UV-initiated thiol-ene reaction, and by a condensation of trans-9,10-epoxystcaric acid with 4(5)-imidazoledithiocarboxylic acid. Nanoparticles (NPs) with 10-100 nm Ag(0) or Co(0) cores were obtained by reduction of Ag+ or Co2+ by borohydride in N,N-dimethylformamide or aqueous solutions respectively. The NPs capped with oleic acid or 9,10-epoxystearic acids were further covalently bound to 2-mercaptoimidazole or 4(5)-imidazoledithiocarboxylic acid. The ligands and NPs functionalized with nucleophilic imidazole moieties enabled facile hydrolysis of paraoxon (O,O-diethyl O-(p-nitrophenyl) phosphate) by NPs in their aqueous media. The NPs acted as recoverable semiheterogeneous catalysts. The paraoxon hydrolysis was accelerated 10- to 50-fold by the formation of complexes between the imidazole-containing ligands or NPs with Co2+.