Effect of surface modifications on the decoration of multi-walled carbon nanotubes with ruthenium nanoparticles

Different surface modifications of multi-walled carbon nanotubes (MWCNTs), including concentrated acid treatment, surface adsorption of an anionic surfactant, and activation by metal cations, were used to investigate their effects on the decoration of MWCNTs with ruthenium nanoparticles prepared by the reduction of ruthenium chloride in ethylene glycol. Surface adsorption of sodium dodecyl sulfate (SDS) enabled the decoration of MWCNTs with a monolayer of uniform ruthenium nanoparticles on the surface. Infrared spectroscopy analysis of the Ru-decorated MWCNTs provided direct evidence for the strong interaction between the ruthenium nanoparticles and the nanotubes. Similar results were achieved by the activation of acid-treated MWCNTs with Ni2+. The superior amount of decoration is interpreted in terms of the bridging role of SDS surfactant in increasing the number of active sites for the adsorption and nucleation of ruthenium nanoparticles, and the crucial role of nickel clusters in facilitating the heterogeneous growth of ruthenium nanoparticles.