AGGREGATES OF C-60 AND C-70 FORMED AT THE GAS WATER INTERFACE AND IN DMSO WATER MIXED-SOLVENTS - A SPECTRAL STUDY

The absorption spectra of pure spread films of C60 and C70 as well as mixtures Of C60 or C70 with 1,2-dioleoyl-sn-glycerol, DOG (C60/DOG or C70/DOG = I/ 1, 1/4, 1/20), have been measured at the nitrogen-water interface. These spectra resemble those Of C60 and C70 solid films rather than spectra reported in nonaqueous solvents. The data suggest that aggregates of fullerene molecules form in spread films on the water surface. Even in C60/DOG (or C70/DOG) 1/20 mixed spread films, the fullerene molecules exist in microdomains rather than homogeneous 2-dimensional solutions. Aggregate formation for C60 and C70 in DMSO/water mixed solvents has also been investigated. At low water volume fraction, phi (<0.10), the spectrum of C60 (1 x 10(-6) M) is that of monomer as observed in cyclohexane or benzene. Increasing phi to >0.10 leads to spectra resembling those of spread films. At a constant phi of 0.40, an increase in C60 concentration above 10(-7) M gives similar results.