Synthesis and Characterization of Magnetic Nanoparticle-Decorated Multiwalled Carbon Nanotubes

Multiwalled carbon nanotubes find applications in many fields due to their extraordinary properties. However, depending on their synthesis method, they show no or a poor response to the presence of a magnetic field. This limits their usability in magnetic applications. In this study, the maximum induced magnetization of multiwalled carbon nanotubes was increased by deposition of magnetic nanoparticles, which were produced by nanosecond pulsed laser deposition under inert low-pressure conditions using iron (Fe), magnetite (Fe₃O₄), cobalt (Co), and nickel (Ni) targets. Extensive chemical and physical characterization of the added nanoparticles was performed. It was found that for the same synthesis conditions, Fe and Fe₃O₄ targets resulted in the formation of larger, asymmetrical magnetic Fe nanoparticles with a Fe₃O₄ shell (Fe@Fe₃O₄) (3.2-8.6 nm) and Fe₃O₄ (6.0-12.4 nm) nanoparticles, respectively. Smaller, more spherical Co@CoO (2.1-5.0 nm) and Ni@NiO (1.4-3.5 nm) nanoparticles were obtained from the Co and Ni targets, respectively. The highest increase in maximum induced magnetization was observed for multiwalled carbon nanotubes with Fe@Fe₃O₄ (5.37 ± 0.15 emu/g) or Co@CoO nanoparticles (4.29 ± 0.01) compared to pristine multiwalled carbon nanotubes (2.46 ± 0.08 emu/g) and nanotubes with Fe₃O₄ (3.79 ± 0.38 emu/g) or Ni@NiO nanoparticles (2.85 ± 0.06 emu/g). Finally, superior adhesion of the Fe@Fe₃O₄ and Fe₃O₄ nanoparticles to multiwalled carbon nanotubes compared to the Ni@NiO and Co@CoO nanoparticles was identified.