Features of self-aggregation of C60 molecules in toluene prepared by different methods

•Structural and dimensional features of C60C60 aggregates in toluene solution prepared in two different ways – equilibrium and strongly non-equilibrium – were studied by high-resolution transmission electron microscopy and atomic-force microscopy methods.•Six characteristic absorption bands with maxima at λ1≈335 nmλ1≈335 nm (symmetry-allowed transition 11Ag−31T1u11Ag−31T1u), λ2≈351 nmλ2≈351 nm (91T1g−181T1u91T1g−181T1u), λ3≈407 nmλ3≈407 nm (11Ag−11T1u11Ag−11T1u), λ4≈534 nmλ4≈534 nm (S1→S3S1→S3), λ5≈598 nmλ5≈598 nm (vibronic structure of S0S0–S1S1 transition), and λ6≈625 nmλ6≈625 nm (hu→t1u+Tuhu→t1u+Tu) have been observed.•The nature of the first two mutually competing optical absorption bands with maxima at λ1≈335 nmλ1≈335 nm and λ2≈351 nmλ2≈351 nm is related to the processes of intermolecular dipole–dipole π∼π⁎π∼π⁎ interactions “fullerene–toluene” and “fullerene–fullerene”, correspondingly.•The absorption band with a maximum at λ1≈335 nmλ1≈335 nm occurs only at low concentration of C60C60 in the solution (∼0.11 mol/m3∼0.11 mol/m3) and disappears at higher concentrations of fullerene (0.44÷1.33 mol/m30.44÷1.33 mol/m3).•Thus, short-wave part of the absorption spectrum of C60C60 solution (300÷410 nm300÷410 nm) is very sensitive to the formation of molecular aggregates in (C60)m(C60)m solution. Long-wave part of the spectrum (410÷700 nm410÷700 nm), arising from electronic transitions HOMO-LUMO, while maintaining high sensitivity to the formation of (C60)m(C60)m aggregates in the solution, also allows to predict synthesis of (C60)m(C60)m aggregates due to the charge transfer between C60C60 molecules.

Structural and dimensional features of C60C60 aggregates in toluene solution prepared in two different ways – equilibrium and strongly non-equilibrium – were studied by high-resolution transmission electron microscopy and atomic-force microscopy methods. It was found that in solutions prepared by the non-equilibrium method (stirring of solution of C60C60 by a mechanical rotator), large quasispherical aggregates (with a diameter of up to ∼380±20 nm∼380±20 nm) of nanoporous structure with fractal size D≈2.13D≈2.13 were synthesized. In the case of solutions C60C60, which were prepared by the equilibrium method (without the use of external mechanical influences on solution), the formation of densely packed monomolecular fullerene aggregates with a diameter of not more than 50 nm was observed.