Characterization of single-walled carbon nanohorns using neon adsorption isotherms

Detailed volumetric neon adsorption isotherms were measured between 22.670 and 31.444 K on a sample of closed, mostly bud-like, aggregates of single-walled, carbon nanohorns, produced by NanoCraft, Inc. The results are compared to those recently reported on closed dahlia-like nanohorn aggregates. While for the closed dahlia-like aggregates the data shows that there are two groups of sites with different binding energies present at relatively low loadings, only one group of adsorption energies is present for the closed bud-like aggregates at comparable loadings. We measured the isosteric heat of adsorption and its dependence on substrate loading. From the low-loading limit of this quantity, we determined that the binding energy of the sites present on the bud-like aggregates have a value intermediate between that obtained for adsorption on planar graphite and that measured on the grooves of close-ended bundles on nanotubes for the same adsorbate.