The behavior of intermolecular interactions in fresh and aged solutions of fullerene C60 in neat N-methyl-2-pyrrolidone (NMP), as well as in NMP/xylene mixed solvents, were studied by the methods of ultraviolet-visible spectroscopy and dynamic light scattering (DLS). It has been experimentally shown that the aging of the C60/NMP solution leads to the disappearance of the characteristic maximum of molecular absorption at ∼330 nm with smoothing, as well as to an increase in the optical absorption intensity. The latter depend on the formation of “C60- NMP”complexes, as well as on the transition of fullerene molecules to the nanocluster state. Increasing the xylene content in the C60/NMP leads to significant changes in charge transfer between solute and solvent (“C60-NMP”, “C60-C60”) at a fixed concentration of fullerene. The latter leads to the reorganization of nanoparticles, which proceeds with the destruction of molecular complexes. In this case, using the DLS method, it was found that the geometric dimensions of the synthesized C60 nanoclusters decrease.

The dynamics of changes in the values of the refractive index of solutions of C60 in xylene at various concentrations has been studied by the refractometric method. It was found that the deviation from the linear form of the dependence of the refractive index on the C60 concentration occurs at a C60 concentration of 1.8 mg/ml. The deviation is associated with the largest number of molecular interactions between C60−C60 and the formation of large nanoclusters on their basis in solution. It was found by the dynamic light scattering (DLS) that the final size of C60 nanoclusters in solution depends on the initial concentration of the solute. A higher initial concentration of C60 leads to the synthesis of nanoclusters with a larger diameter. Using the method of optical spectroscopy, the processes of self-organization of fullerene C60 molecules in a xylene solution in time are studied. The character of stability of synthesized fullerene nanoclusters in solution is discussed. The results obtained are of particular importance for numerous applications of nanotechnology for understanding self-assembly processes and the development of new nanomaterials.