Interactions of Nanosized Aggregates of Fullerene C-60 with Electrolytes in Methanol: Coagulation and Overcharging of Particles

摘要

Contrary to numerous studies on the stability of fullerene aqueous colloidal solutions in the presence of electrolytes, the corresponding issue for the organosols was until recently almost unexplored. In this article, the state of C-60 in methyl alcohol and the regularities of the coagulation of colloidal solution in this solvent were examined in the presence of electrolytes. Alcosols with a fullerene concentration of 4 X 10(-6) M were prepared by the dilution of the C-60 saturated, solution in toluene by methanol. The ca. 300 nm-sized aggregates possess a negative electrokinetic potential value, zeta =-37 +/- 8 mV. To deterinine the critical coagulation concentrations, CCC, the size increase of the species was followed up using the dynamic light scattering method. The analysis of the coagulation in terms of the Fuchs function, W, was accompanied by zeta potential monitoring: The consideration: of-the data for 1:1 electrolytes NaClO4 and N(n-C4H9)(4)ClO4 allows a rough estimate of the Hamaker constant of fullerene-fullerene attraction. Whereas in the case of these two electrolytes the colloidal species are negatively charged at the CCC, expressed overcharging of up to zeta = +36 mV by H+, Ca2+, Ba2+, and La3+ ions was observed. The action of HClO4 should be attributed to the interfacial acid-base reaction, whereas the excessive attraction of metal cations is caused by poor solvation in methanol; the negative charge is restored when the metal cations are shielded by a macrocyclic ligand.