Fabrication of "tadpole"-like magnetite/multiwalled carbon nanotube heterojunctions and their self-assembly under external magnetic field.

Novel "tadpole"-like Fe3O4/multiwalled carbon nanotube (MWCNT) heterojunctions were successfully synthesized by position-selectively attaching Fe3O4 sphere on the tips of MWCNTs through a straightforward and effective polyol-medium solvothermal method. Transmission and scanning electron microscopy (TEM and SEM) and X-ray diffraction (XRD) investigations show these Fe3O4 spheres are constructed with tiny nanocrystallites (approximately 5 nm in average diameter), which were preferentially aggregated in an oriented pattern on the open ends of the MWCNT template. Magnetic investigation indicates this novel Fe3O4/MWCNT hybrid presents superparamagnetic behavior. The size and corresponding magnetic performance of these magnetite/MWCNT hybrids can be adjustable to some extent for specific applications through altering the reaction parameters. Furthermore, these tadpolelike nanocomposites can orient and self-assemble into one-dimensional structure under external magnetic field, displaying great potential in precise manipulation and organization of carbon nanotube-based structures into integrated functional system.