This
paper is aimed at better understanding the nature of C70 aggregates in organic solvents. As liquid media, acetonitrile–toluene
mixed solvents were chosen. At a high content of CH3CN,
e.g., 90 vol %, colloidal particles with a size of ca. 225 ±
10 nm are formed with a negative ζ-potential of −(55
± 5) mV and are stable over time. The interaction with electrolytes
containing single-, double-, and triple-charged cations was examined
using dynamic light scattering and UV–visible spectra. Additional
experiments were carried out with methanol and benzene instead of
acetonitrile and toluene, respectively. For comparison, data were
obtained with C60 organosols. It was found that coagulation
obeys the classical Schulze–Hardy rule. The specificity of
the coagulating power of various single-charged cations was explained
by their different abilities to adsorb on negatively charged C70 aggregates. The overcharging effect is expressed not only
for Ca2+ and La3+ ions but even for Li+ and is caused by poor solvation of such cations in a cationophobic
solvent, acetonitrile. After introduction of the cryptand [2.2.2],
a substantial increase in the critical concentrations of coagulation
for Na+, Li+, and Ca2+ was observed
owing to conversion of “bare” metal cations into their
cryptates. The application of the Derjaguin–Landau–Verwey–Overbeek
theory allowed for evaluation of the Hamaker constant of the C70–C70 interaction in vacuum, A
FF, which lies in the interval of 5.8–16.6 ×
10–20 J. Such an estimate, close to that made previously
for C60 organosols, was received after withdrawing electrolytic
systems where the hetero- and mutual coagulation were highly likely.
However, it is impossible to completely exclude the interfering influence
of the latter phenomena. Based on the obtained A
FF values, two approaches to understanding the behavior of
fullerenes in water were proposed.