Nanoscale Electroless Metal Deposition in Aligned Carbon Nanotubes

Arrays of aligned, multiwalled carbon nanotubes were produced by catalytically pyrolyzing acetylene within the pores of an anodic aluminum oxide template. Small cobalt catalyst particles were predeposited electrochemically at the bottom of the pores. The tube walls consisted of approximately 10 carbon layers with an interlayer spacing of approximately 3.45 Å, somewhat larger than the 3.35 Å interplanar spacing of graphite. The nanotubes were found to be open at one end, making it possible fill the tubes with metals or other materials. Nickel and cobalt metals were deposited in the interior of the tubes using nanoscale electroless deposition. The deposited metals included small quantities of phosphorus or boron, according to the reducing agent used in the electroless deposition process (hypophosphite or dimethylamine−borane). The deposits in general consisted of discontinuous, polycrystalline metal filling most of the length of the nanotube, but in the case of Co reduced with hypophosphite, continuous polycrystalline deposits of up to 3 μm were observed. The Ni crystallites inside the tubes had fcc structures with cell constants of 3.56 Å, slightly larger than the 3.52 Å lattice constant of bulk nickel possibly due to the inclusion of P.