On the synthesis and magnetic properties of multiwall carbon nanotube–superparamagneticiron oxide nanoparticle nanocomposites

Abstract

Multiwall carbon nanotubes (MWCNTs) possessing an average inner diameter of 150 nmwere synthesized by template assisted chemical vapor deposition over an aluminatemplate. Aqueous ferrofluid based on superparamagnetic iron oxide nanoparticles(SPIONs) was prepared by a controlled co-precipitation technique, and this ferrofluidwas used to fill the MWCNTs by nanocapillarity. The filling of nanotubes withiron oxide nanoparticles was confirmed by electron microscopy. Selected areaelectron diffraction indicated the presence of iron oxide and graphitic carbon fromMWCNTs. The magnetic phase transition during cooling of the MWCNT–SPIONcomposite was investigated by low temperature magnetization studies and zero fieldcooled (ZFC) and field cooled experiments. The ZFC curve exhibited a blocking at∼110 K. A peculiar ferromagnetic ordering exhibited by the MWCNT–SPION composite aboveroom temperature is because of the ferromagnetic interaction emanating from theclustering of superparamagnetic particles in the constrained volume of an MWCNT. Thiskind of MWCNT–SPION composite can be envisaged as a good agent for variousbiomedical applications.