Saranjit Kaur1, Stuart L. Belli2, and Christopher J. Smart2. (1) Cornell University, Ithaca, NY, (2) Vassar College, Poughkeepsie, NY
Carbon nanotubes have unique electrical, mechanical and chemical properties, which makes them attractive materials for a wide variety of applications. Challenges faced when integrating nanotubes into electronic and electrochemical devices are high contact resistance between the carbon nanotube and contacting metal wire, and large double-layer capacitance between the nanotube and electrolyte. This study is concerned with mitigating these limitations using a novel combination of deposition techniques: nanotubes were grown on nickel-plated gold and copper wire substrates using chemical vapor deposition (CVD) from acetylene as the precursor gas. The films grown on the Au/Ni substrates were thicker and more reproducible than those grown on Cu/Ni. These carbon-coated wires were subsequently used as substrates for electrodeposition of pure gold from a commercially-available plating bath. We observed deposition of spherical gold nanoparticles (50-200 nm in diameter) on both the ends and isolated locations on the sidewalls of CVD nanotubes. Our hypothesis is that electrodeposition occurs at sites along the conductive nanotube where free electrons are available, perhaps at defects or some other special feature. Regarding nanotube structure, electrodeposition does show preferential nucleation of Au particles on the walls of straight tubes compared to helical or tangled tubes. Cyclic voltammetry was used to characterize the behavior of the Au-particle decorated nanotubes as electrochemical electrodes. The nanotube-covered Au wires exhibited comparable faradaic current and significantly higher non-faradaic charging when compared with bare Au wires. CV results indicate that these nanotube-covered wires can serve as both sensitive electrochemical electrodes and supercapacitors, in addition to electrically-connected nanowires.
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