Fullerene derivatives encapsulated in carbon nanotubes

We report on the preparation and subsequent Raman analysis of carbon nanotube peapods, using the fullerene C₆₀ and its heterofullerene derivative (C₅₉N)₂ as filling materials. The filling with (C₅₉N)₂ was done from liquid solution at room temperature and from the gas phase at elevated temperatures. The success of the encapsulation procedure is confirmed through the identification of fingerprint Raman modes and the conversion to double wall nanotubes through heating to 1250 °C. The 2D mode of double wall nanotubes made from (C₅₉N)₂ peapods is observed to be downshifted compared to the same mode in double wall nanotubes made from C₆₀ peapods. We interpret this downshift as an evidence for the integration of the nitrogen into the lattice of the inner tube.