A novel strategy to fabricate γ-Fe2O3-MWCNTs hybrids with selectively ferromagnetic or superparamagnetic properties

Magnetic γ-Fe2O3-MWCNTs hybrids possess a wide range of potential applications. This paper reports a novel and efficient method to fabricate the magnetic γ-Fe2O3-MWCNTs hybrids, via the vacuum thermolysis of Fe(CO)5 confined in/around MWCNTs and subsequent controlled oxidation. It was found that γ-Fe2O3 nanoparticles with controllable sizes could be uniformly nucleated on both the inner and outer surfaces of MWCNTs. The mean sizes of the γ-Fe2O3 nanoparticles here can be varied from 6 to 15 nm by simply modify the experimental process, rendering the hybrids tunable magnetic properties from ferromagnetism to superparamagnetism. It was demonstrated that this method could be used to obtain various metals/oxides-MWCNTs hybrids by simply substituting the metal carbonyl precursors.