We report the results of a carbon-13 nuclear magnetic resonance spectroscopic investigation of the structure of carbon nanohorn aggregates (CNHs). The results show that CNHs consist of two components, characterized by different chemical shifts and spin lattice relaxation (T-1) behavior. The first component has a chemical shift of 124 ppm and displays rapid spin-lattice relaxation behavior and is assigned to the nanotubelike horns on the particles' surfaces. The second component has a chemical shift of 116 ppm and much slower spin-lattice relaxation behavior and is assigned to the graphitelike part of the CNH aggregrate. The results of integrated peak area measurements indicate a 1:2 ratio of nanohorns to the graphitelike substrate. The absence of a clear Korringa behavior for the temperature dependence of T-1 and the lack of a Knight shift ruled out any metallic behavior and indicated instead behavior characteristic of semiconductor materials with paramagnetic centers due to structural defects providing an effective relaxation mechanism in the nanohorn domains. We also observed an anomalous change in T-1 near 17 K in the nanohorn domains suggesting the development of an antiferromagnetic correlation between localized electron spins.

We present in this report a new type of particles with micrometer-order sizes, which we called giant graphitic balls (GG balls). The GG balls are produced by CO2 laser ablation of graphite together with single-wall carbon nanohorns. They have graphitic structures whose layers tend to align parallel with the GG-ball surfaces, resulting in polygonal-like arrangements. Comparing the GG-ball structure with that of the previously reported polygonal graphite-particles, the growth mechanism of the GG ball is discussed briefly.

La surface laterale d'une tige de graphite (101) est irradiee au moyen d'une lumiere laser (103) servant a evaporer le carbone afin de generer une plume (109). Le carbone evapore est conduit dans une chambre de recuperation (119) de nano-cornets de carbone via un tube de recuperation (155) et est recupere sous forme d'un ensemble de nano-cornets (117) de carbone. Un reservoir de refroidissement (150) regule la temperature de la plume (109) afin de la maintenir en position basse et de refroidir la vapeur de carbone pendant son passage a travers le tube de recuperation (155). La vapeur de carbone refroidie est recuperee sous forme d'ensemble de nano-cornets (117) de carbone commandes afin de presenter la forme et la dimension desirees.

Material storage in the inner spaces of nanocarbon materials is visualized for the first time. It is shown that creating paths of a specific size to the inner space (see Figure) is indispensable for material storage in carbon nanopores, and that the adsorption rate for fullerene molecules is largely dependent on the nanoscale curvature of the graphitic planes composing the nanospaces.