Spectroscopic characterization of fullerenes (C60, C70) in polymeric states

The vibrational spectra of polymerized C60 and C70 fullerenes are studied by Raman spectroscopy. All the samples were synthesized under different pressure - temperature (p-T) conditions in a piston and cylinder device (not subject of this work. Diode Pumped Solid State (DPSS) laser (532nm) and HeNe laser (633 nm) were used for excitation. With HeNe laser excitation, very weak Raman signals were observed in case of both polymerized and monomeric samples due to high fluorescence. In contrary, using 532nm laser excitation, C60 was successfully characterized in its polymeric form which was identified via shift of vibrational modes and/or appearance of new Raman – active modes. Despite the similarities in the Raman spectra of 1-Dimensional (1D) and 2- Dimensional (2D) C60 polymers some differences in the Raman peak positions were identified. More importantly, we were able to distinguish between 1D and 2D polymers via the amplitude of pentagonal pinch mode (Ag(2)) peak position shift. The C60 samples under investigation exhibit multiphase structure due to quasi non-hydrostaticity of pressure during the high p-T synthesis. It was difficult to characterize high p-T treated C70 samples even with with 532 nm laser excitation - no evident shift of Raman modes was observed. It implies that FT Raman spectroscopy with IR excitation is needed for characterization of polymeric structures generated in C70 at high p-T.Validerat; 20101217 (root