Time Evolution of the Optical and Structural Properties of C70 Fullerene in Benzene–Cyclohexane Solvents

In this study, we comprehensively investigated the aggregation processes of fullerene C70 in a benzene/cyclohexane binary solution, taking into account the effects of concentration and time. The optical properties of the samples were analyzed using UV-visible and Raman spectroscopy, as well as refractometry (n and BRIX parameters). The preservation of the positions of specific maxima of C70 unchanged in the UV-visible spectra indicates that the aggregation process does not disturb the fundamental electronic structure of the molecule. Raman analysis showed that the increase in the intensity of some vibrational modes and a decrease in the number of peaks over time are associated with physical clustering processes. Refractometric results showed that the refractive index increases with increasing C70 concentration. Although the UV–Vis absorption intensity continues to increase up to the 20th day, the refractive index and BRIX values exhibit only minor variations in the 15–20 day interval, indicating that the system approaches a dynamic optical equilibrium in terms of refractometric response. It was noted that aggregation occurs faster in the sample with a higher concentration.

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