Alignment of Carbon Nanotubes under Low Magnetic Fields through Attachment of Magnetic Nanoparticles

Miguel A. Correa-Duarte, Marek Grzelczak, Verónica Salgueiriño-Maceira, Michael Giersig, Luis M. Liz-Marzán, Michael Farle, Karl Sierazdki, and Rodolfo Diaz

J. Phys. Chem. B, 2005, 109, 19060–19063

The alignment of multiwalled carbon nanotubes (MWNTs) has been accomplished through deposition of uniform layers of magnetite/maghemite nanoparticles (diameter = 6−10 nm) and use of an external magnetic field. The coating of CNTs with magnetic nanoparticles was performed by combining the polymer wrapping and layer-by-layer (LbL) assembly techniques. The particle-coated MWNTs are superparamagnetic and can be aligned at room temperature on any substrate by deposition from an aqueous solution in an external field B = 0.2 T. The volume magnetization of the particle coated MWNTs is found to be enhanced by 17% compared to the pure particles in a powder indicating that either the adsorption process onto the CNTs changes the particle magnetization, or the MWNTs carry an intrinsic magnetization due to remaining Ni used as a catalyst for the growth process.