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 C70. 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.