Influence of an Extended Fullerene Cage:  Study of Chemical and Electrochemical Doping of C₇₀ Peapods by in Situ Raman Spectroelectrochemistry

C 70 peapods (C 70 @SWCNT) have been studied for the first time under chemical and electrochemical doping by in situ Raman spectroelectrochemistry. The bleaching of Raman features of single-walled carbon nanotubes (SWCNT) and the downshift of the frequency of their tangential mode confirmed the strong chemical doping of C 70 @SWCNT by potassium vapor. The changes of C 70 band intensities and positions upon K-vapor doping indicate the insertion of potassium into the interior of a peapod and the chemical reduction of C 70 . The subsequent treatment of the K-doped peapod with water caused only a partial dedoping as the potassium outside the peapod is removed while that inside the tube remains intact. Electrochemical charging of the partially dedoped C 70 peapods differs from that of C 60 @SWCNT. The most striking feature was the enhancement of the C 70 -related Raman bands during anodic charging. The results are interpreted in terms of different electronic structures of C 60 and C 70 peapods, and their specific feedback to chemical and electrochemical doping.