Superconducting fullerene nanowhiskers.

We synthesized superconducting fullerene nanowhiskers (C(60)NWs) by potassium (K) intercalation. They showed large superconducting volume fractions, as high as 80%. The superconducting transition temperature at 17 K was independent of the K content (x) in the range between 1.6 and 6.0 in K-doped C(60) nanowhiskers (K(x)C(60)NWs), while the superconducting volume fractions changed with x. The highest shielding fraction of a full shielding volume was observed in the material of K(3.3)C(60)NW by heating at 200 °C. On the other hand, that of a K-doped fullerene (K-C(60)) crystal was less than 1%. We report the superconducting behaviors of our newly synthesized K(x)C(60)NWs in comparison to those of K(x)C(60) crystals, which show superconductivity at 19 K in K(3)C(60). The lattice structures are also discussed, based on the x-ray diffraction (XRD) analyses.

Surface breakdown dynamics of carbon nanocapsules.

The structural variation in a single-molecule junction consisting of a hollow multi-walled carbon nanocapsule sandwiched between two gold electrodes during the breakdown of the outermost wall layer was observed in situ by high-resolution transmission electron microscopy. Simultaneously, the current-voltage curve of the junction was measured. The differential conductance of the junction decreased discontinuously from 1G(0) (where G(0) = 2e(2)/h is the conductance quantum, e is the electron charge and h is Planck's constant) to 0.5 G(0) and then to 0.2G(0) when the total number of wall layers decreased from four to three owing to the breakdown of the outermost layer. The maximum current decreased by 19 microA when the differential conductance decreased discontinuously. Our direct observation of the correlation between the atomistic structure and the conductance provides evidence for electron transport through several layers of the multi-walled nanocapsule, similar to that through carbon nanotubes with their surface in contact with electrodes.