COLLOIDAL DISPERSIONS OF FULLERENE C-60 IN WATER - SOME PROPERTIES AND REGULARITIES OF COAGULATION BY ELECTROLYTES

The ultramicroheterogeneous dispersion of buckminsterfullerene, C-60, in water was found to be a typical hydrophobic colloidal system. The s tudied sol was polydisperse (d from several nanometers to ca. 200 nm), with negatively charged surfaces of the particles. The coagulation by inorganic electrolytes occurs in accordance with the Schulze-Hardy ru le; the reciprocal coagulation points for counter-ion charges z = 1, 2 and 3 are related as approximate to 1 :20:1500. The results are discu ssed in terms of the Derjaguin-Landau-Verwey-Overbeek theory. In the c ase of organic electrolytes, including colloidal cationic surfactants, their coagulation points decrease with increasing hydrophobicity and surface activity of the cations. An excess of cetyltrimethylammonium b romide stabilises the fullerene dispersion. The coagulating action of the tetrabutylammonium ion depends on the nature of the co-ion. Polyvi nyl pyrrolidone and sodium dodecyl sulfate protect the C-60 sol from c oagulation.