In situ synthesis and electronic transport of the carbon-coated Ag@C/MWCNT nanocomposite.

A nanocomposite of Ag@C nanocapsules dispersed in a multi-walled carbon nanotube (MWCNT) matrix was fabricated in situ by a facile arc-discharge plasma approach, using bulk Ag as the raw target and methane gas as the carbon source. It was found that the Ag@C nanocapsules were ∼10 nm in mean diameter, and the MWCNTs had 17-32 graphite layers in the wall with a thickness of 7-10 nm, while a small quantity of spherical carbon cages (giant fullerenes) were also involved with approximately 20-30 layers of the graphite shell. Typical dielectric behavior was dominant in the electronic transport of Ag@C/MWCNT nanocomposites; however, this was greatly modified by metallic Ag cores with respect to pure MWCNTs. A temperature-dependent resistance and I - V relationship provided evidence of a transition from Mott-David variable range hopping [ln  ρ ( T ) ∼ T -1/4 ] to Shklovskii-Efros variable range hopping [ln  ρ ( T ) ∼ T -1/2 ] at 5.4 K. A Coulomb gap, Δ C ≈ 0.05 meV, was obtained for the Ag@C/MWCNT nanocomposite system.