Direct synthesis of carbon nanotubes decorated with size-controllable Fe nanoparticles encapsulated by graphitic layers

A simple method has been developed for direct synthesis of magnetic multi-walled carbon nanotubes (MWCNTs) homogeneously decorated with size-controllable Fe nanoparticles (Fe-NPs) encapsulated by graphitic layers on the MWCNT surface by pyrolysis of ferrocene. These composites have similar C/Fe atomic ratio of ∼10 and exhibit sufficiently high saturation magnetization for magnetic separation in a liquid phase. Moreover, with 0, ∼1, ∼2 wt% sulfur as growth promoter, the size of Fe-NPs can be controlled with an average diameter of ∼5, ∼22 and ∼42 nm, respectively. When compared to time-consuming wet-chemical methods, the simplicity of this method should allow easy large-scale production of these magnetically functionalized MWCNTs, which can be used as catalyst supports with high stability for effective magnetic separation in liquid-phase reactions, especially under acid/basic conditions.