Synthesis, separation, and isolation of [6,6]-closed epoxide of fullerene using semi-preparative high performance liquid chromatography and preparation of aqueous colloidal suspensions

Fullerenes are among the most attractive carbon nanomaterials and have wide-spread applications including electronics, automobile, aircraft, and energy. C60 has a tendency to form stable colloidal aggregates (also known as, nano-C60 or nC60) in most aqueous conditions, making the nC60 form an important staring point and a fundamental model for comparing all fullerene impact studies. nC60 has been shown to induce toxicity in numerous cell cultures and whole animal systems. However, contradictory reports in the literature make it difficult to interpret the mechanism by which fullerene toxicity is induced. nC60 suspensions are demonstrated to rely on the [6,6]-closedepoxide (C60O) derivative of the fullerene for stability. It is important to investigate the role of C60O in the observed oxidation behavior of fullerene aqueous suspensions. Our goal of this project is focused on the synthesis, separation, and isolation of C60O using semi-preparative high performance liquid chromatography, and preparation of colloidal suspensions. In the present study, we have successfully synthesized oxides of fullerene by ozonating solutions of C60 in toluene under ambient conditions. Excellent separation between C60, C60O, and C60O2 was achieved by using a mixture of toluene/n-hexane mobile phase in a Nacalai Cosmosil Buckyprepsemi-preparative column. Separated compounds were successfully isolated and analyzed by UVVis spectroscopy. The wavelengths of maximum absorbance were determined to be 336, 328, and315 nm for C60, C60O, and C60O2, respectively and are in agreement with literature reported values. Ultimately, successful synthesis of aqueous suspensions of C60O was achieved, and the colloid composition was confirmed to be purely C60O. Aqueous colloidal suspensions of C60O have an average hydrodynamic diameter of 140 ? 20 nm, with a PDI of 0.28 ± 0.05. To the best of our knowledge this is the first report of successful synthesis of colloidal suspensions of pure C60O