Investigation on the aggregation properties of cationic [60]fullerene derivative

The UV-Vis spectra, HRTEM and AFM images of cationic fullerene derivative 1 with ammonium head group directly connected to C₆₀ skeleton in tetrahydrofuran (THF)-water (H₂O) binary mixtures and in pure H₂O were investigated. It was found that the UV-Vis spectra of ammonium 1 in the THF-H₂O mixtures with THF% ⩾ 20% were nearly overlapped, while those with THF% < 20% showed broadened and red-shifted peaks, indicating the formation of aggregates. Corresponding to the UV-Vis spectral changes, the solvatochromism of ammonium 1 in THF-H₂O mixtures was observed. Ammonium 1 in binary THF-H₂O mixtures existing as the monomer state could aggregate upon prolonged standing. Higher temperature and lower concentration speeded up the aggregation process.