Single-step functionalization of vertically aligned MWCNTs with Cu and Ni by chemical reduction of copper and nickel acetyl acetonate in benzyl alcohol

We report a one-step functionalization reaction of forests of vertically aligned multi-walled carbon nanotubes (MWCNTs) with Cu or Ni nanoparticles. The benzyl alcohol assisted deposition reaction reduces copper or nickel acetyl acetonate to metallic homogeneously distributed nanoparticles and a 1 μm thick metallic capping layer normal to the MWCNT forests. Scanning electron microscopy and transmission electron microscopy images reveal a trimodal diameter regime for the Cu nanoparticles and a bimodal distribution for the Ni nanoparticles. Electron energy loss spectroscopy (EELS) and X-ray diffraction measurements confirm the metallic form of the particles and layers; however EELS reveals surface oxidation of the Cu particles. The metallic layer on top of the functionalized MWCNT forests can serve as a back contact and is deposited simultaneously with the nanoparticles. Field emission measurements reveal a lower contact resistance than for samples prepared by metal sputtering. Comparison with a sputtering process shows the uniqueness of this new Cu functionalization method for CNTs.