Spectroscopic characterisation of the C₆₀ photo-polymer produced from solution

The Raman scattering signal of C₆₀ in solution was monitored at a quartz cuvette interface as a function of the excitation intensity at 514.5nm. The ground state Raman mode, at 1469cm^-1 in solution was seen to degrade quickly under illumination to a lower Raman frequency of 1458cm^-1 whereby an insoluble deposit formed on the cuvette face. The deposit has been identified using Raman spectroscopy as a photochemical product of C₆₀ analogous to the solid state C₆₀ polymer formed by a 2+2 cycloaddition across π bonds of neighbouring molecules. In the solid state a number of pressure induced and photo-induced polymeric phases are known to exist. However the exact nature of the photo-induced polymeric phase in the solid is still unclear. In this study Raman scattering, IR spectroscopy and TEM have been used to attempt to classify the C₆₀ photopolymer produced from solution. The results indicate a complex mixture of phases, which reduce the molecular symmetry and enrich the Raman and IR spectra.