Synthesis, characterization, and alignment of magnetic carbon nanotubes tethered with maghemite nanoparticles

In this work we describe a novel, facile method for the decoration of multiwalled carbon nanotubes (MWNTs) with nearly monodisperse γ-Fe ₂O₃ magnetic (maghemite) nanoparticles and their alignment in a magnetic field. The tethering of the nanoparticles was achieved by the initial activation of the surface of the MWNTs with carboxylic acid groups, followed by the attachment of the γ--Fe₂O₃ nanoparticles via their synthesis using a modified sol-gel proess. Sodium dodecylbenzenesulfonate (NaDDBS) was introduced into the suspension as a surfactant in order to prevent the formation of an iron oxide 3D network. Various characterization methods were used to confirm the formation of well-defined maghemite nanoparticles and show that they were tethered to the walls of the MWNTs. The tethered γ-Fe₂O₃ nanoparticles imparted magnetic characteristics to the MWNTs and allowed their alignment in the direction of an externally applied magnetic field. This facile alignment of MWNTs could promote the enhancement of various properties, e.g., mechanical or electrical properties, of the resulting composites.