One-Dimensional Metallofullerene Crystal Generated Inside Single-Walled Carbon Nanotubes

Electron microscope imaging for gadolinium metallofullerenes encapsulating in single-wall carbon nanotubes $\left[\right(\mathrm{Gd}@\mathrm{C}{}_{82}{)}_n@\mathrm{SWNTs}]$ identifies the single Gd atom encaged in each. The intermolecular distance between $\mathrm{Gd}@\mathrm{C}{}_{82}$ is extremely regular, regarding the chains of $\mathrm{Gd}@\mathrm{C}{}_{82}$ as novel one-dimensional crystals. Chemical state analysis of Gd atoms suggests evidence for charge transfer from Gd to either a fullerene cage or a nanotube. The slopes of the temperature dependence of electric resistance for the matlike films of $(\mathrm{Gd}@\mathrm{C}{}_{82}{)}_n@\mathrm{SWNTs}$ and $(\mathrm{C}{}_{60}{)}_n@\mathrm{SWNTs}$ are much steeper than that for empty SWNTs, suggesting the electron scattering due to the electrostatic potential from inside fullerenes playing an important role.