Analysis of the concentration of C60 fullerenes in single wall carbon nanotubes

Single wall carbon nanotubes filled with C-60 were analyzed using resonance Raman scattering and electron energy loss spectroscopy. In order to obtain concentrations of the fullerene molecules inside the tubes, the scattering intensity from the fullerenes relative to that from the tubes was used. Since the scattering intensity from the tubes is subject to strong fluctuations, the determination of the concentrations is shown to require averaging of results from different lasers and from all observable Raman lines. The fluctuations are shown to be intrinsic and a consequence of photoselective resonance scattering. Calibration of absolute concentrations can be obtained from electron energy loss spectroscopy performed on the same samples. Samples with three different diameters were analyzed and good agreement between the fullerene concentrations measured by the two methods was obtained.