Abstract
In the present study, we investigated Cs-intercalated single wall carbon nanotubes (SWCNTs) using Cs-133 Nuclear Magnetic resonance. We show that there are two types of Cs cations depending on the insertion level. Indeed, at low concentrations, Static spectra analysis shows that the Cs(alpha)+ species are fully ionized, i.e. alpha equal cal, while at higher concentrations a second paramagnetically shifted line appears, indicating the formation of Cs(beta)+ ions with beta < alpha similar to +1. At low concentrations and low temperatures the Cs(alpha)+ ions exhibit a weak hyperfine coupling to the SWCNT conduction electrons, whereas, at higher temperatures, a thermally activated slow-motion diffusion process of the Cs(alpha)+ ions occurs along the interstitial channels present within the carbon nanotube bundles. At high concentrations, the Cs(beta)+ ions seem to occupy well defined positions relative to the carbon lattice. As a matter of fact, the Korringa relaxation behavior suggests a strong hyperfine coupling between Cs nuclei and conduction electrons in the carbon nanotubes and a partial charge transfer, which suggest a plausible Cs(6s)-C(2p) hybridization. (C) 2012 Elsevier Ltd. All rights reserved.