Photoemission study of electronic structures of fullerene and metallofullerene peapods

We have investigated the electronic structures of single‐wall carbon nanotubes (SWCNTs) encapsulating C 70 fullerene and metallofullerenes M@C 82 (M = La, Gd, Dy), C 70 peapods (C 70 @SWCNT) and metallofullerene peapods (M@C 82 @SWCNT), using photoemission spectroscopy. The photoemission spectra of C 70 and M@C 82 peas are obtained by subtracting the spectrum of pristine SWCNTs from those of the corresponding peapods. The electronic structure of the C 70 peas is similar to that of the C 70 film. For the M@C 82 peapods, on the other hand, the electronic structures of the M@C 82 peas are different. For the La@C 82 peapods, the singly occupied molecular orbital (SOMO) for the La@C 82 peas is located nearer to the Fermi level when compared with that in the La@C 82 film. For the Dy@C 82 peapods, the effective Dy valence is estimated to be +2.9. This result demonstrates that effective charges move back from the C 82 cage to Dy following encapsulation of Dy@C 82 peas in the SWCNTs because of the strong hybridization interaction between Dy 4 f and C 2 p electrons, taking into account the Dy valence of +3 in the Dy@C 82 film. (© 2008 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)