Aggregation control of hydrophilic maghemite (gamma-Fe2O3) nanoparticles by surface doping using cerium atoms.

The high-power ultrasonic irradiation of preformed magnetite (Fe(3)O(4)) nanoparticles in the presence of monoelectronic Ce-containing ceric ammonium nitrate [Ce(IV)(NH(4))(2)(NO(3))(6)] oxidant in MeCOMe afforded hydrophilic 50 nm-sized colloidal, highly stable maghemite (gamma-Fe(2)O(3)) nanoparticles. An "inorganic" Ce atom doping of the NP surface has been proposed in order to rationalize the observed nanoparticle antiaggregation phenomenon. Quite importantly, this method did not require the use of any organic ligand and/or polymer for the passivation of the nanoparticle surface.