Nondispersive Raman lines in the D-band region for ferrocene functionalized carbon nanotubes

Carbon-rich fillers like ferrocene can be transformed into an inner tube with extremely small diameter if they are filled into HiPco tubes. For ferrocene@HiPco three new Raman bands appear in the D-band region during this transformation. These bands do not show dispersion and exhibit a strong resonance for red laser excitation. The observed resonance is for the outgoing phonon at 1247 cm(-1) for an electronic transition at 1.84 eV. Maximum response for the new lines is observed for transformation of the filled tubes between 800 and 900 degrees C. In addition to the three bands in the D-band region also an enhanced band at 470 cm(-1) is observed with the same sensitivity to transformation temperature. In order to obtain more information on the origin of the new bands deuterium substituted FeCp2 was used. The new lines turned out to be sensitive to this substitution which is considered as a strong indication of their origin from organic compounds created inside or in between the tubes during the transformation process.