SOLUTION BEHAVIOR OF BUCKMINSTERFULLERENE (C-60) IN BENZENE

Solution characterization of buckminsterfullerene C-60 in benzene was carried out by laser light scattering. Static and dynamic light scatte ring (SLS and DLS) experiments were accomplished by using an incident laser beam of 790 nm wavelength, and a fiber optic probe which was cou pled to a RCA C31034 photomultiplier tube sensitive to the near ir wav elength. The effective hydrodynamic radius of C-60 in benzene solution determined by using DLS was 6.4+/-0.1 Angstrom, in close agreement wi th the distance measured from the center of the solvated benzene to th e center of the benzene-solvated C-60 (C-60.4C(6)H(6)):6.7 similar to 6.8 Angstrom as evaluated from the single crystal structure by x-ray d iffraction. C-60 was found to aggregate slowly even in fairly dilute s olution concentrations ranging from 0.78 to 1.39 mg/mL at temperatures 23 similar to 27 degrees C. Based on the high specific refractive ind ex increment of C-60 in benzene, the molar mass of the C-60 aggregates could be estimated. Together with the radius of gyration, the hydrody namic radius, and its size distribution, the kinetics of the aggregati on process was investigated. The aggregation of C-60 in benzene soluti on was reversible, i.e., the C-60 aggregates could be dispersed simply by hand shaking the solution. The light-scattering intensity results indicated that the structure of C-60 aggregates could be described as a fractal with a dimension of 2.10 and the aggregation kinetics exhibi ted essentially an exponential behavior.