PURIFICATION OF C-60 BY FRACTIONAL CRYSTALLIZATION

We describe a new and inexpensive method of purifying C-60 by fraction al crystallization in 1,3-diphenylacetone. After three steps, 99.5% pu re C-60 was obtained with a global yield of 69%. This method is simple r and could be cheaper than any other method presently used. Furthermo re, the purity of C-60 fullerene can be increased up to 99.99% by adso rption of the residual C-70 fullerene on charcoal. The temperature dep endence of the solubility of C-60 and C-70 in 1,3-diphenylacetone was studied and a maximum of solubility was observed at 136 degrees C for C-60 and at 41 degrees C for C-70. This peculiar solubility behaviour is discussed in the light of possible aggregation of C-60 and C-70 mol ecules in the solution phase. (C) 1997 Elsevier Science Ltd.