Surface modification of Fe ₃O ₄ and FePt magnetic nanoparticles with organometallic complexes

Hexane solutions of Fe ₃O ₄ and FePt nanoparticles (NPs) having both oleylamine and oleic acid as surfactants were surface modified by treatment with a DMSO solution of [(η ⁶-hydroquinone)Mn(CO) ₃]BF ₄, which is readily deprotonated by the oleylamine to [(η ⁵-semiquinone)Mn(CO) ₃]. The latter complex binds to the NP by replacing the protonated oleylamine, which likely forms a bilayer with the alkyl chains of the oleic acid on the NP surface. The resulting surface-modified assembly is soluble in DMSO. With FePt nanoparticles, [(η ⁵-semiquinone)Mn(CO) ₃] coordinates to the Pt atoms and the IR frequency of the tricarbonyls differs from that obtained with Fe ₃O ₄ nanoparticles, in which coordination is to the iron.