Physicochemical characterization of fullerenol and fullerenol synthesis by-products prepared in alkaline media

This investigation examined the physicochemical characteristics of a fullerene derivative, fullerenol [C60H (z) O (x) (OH) (y) ] (also known as "polyhydroxyl fullerene") prepared in alkaline media, and its synthesis by-products to enable the assessment of mechanisms and factors influencing biological response. Physicochemical analyses included characterization by dynamic light scattering (DLS) and transmission electron scattering (TEM), surface charge assessment through electrophoretic analysis of mobility, and chemical composition analysis using ultraviolet/visible light, Fourier-transform infrared (FTIR), and X-ray photoelectron spectroscopy. Fullerenol was shown to exist in a molecular state at concentrations below 20 mg/L with agglomeration occur as gas concentration increased; sonication of fullerenol samples at multiple concentrations increased agglomeration. Fullerenol surface group composition varied between three independent synthesis events with the number of total derivatized carbon atoms ranging from 21 to 30 and the number of mono-oxygenated groups ranging from 5 to 20. Surface group configuration was influenced by the acidity of the solution in which it was synthesized, as determined through FTIR. By-products from fullerenol synthesis contained 17 to 30 surface groups and synthesis reactants tetrabutylammonium hydroxide (TBAH) and sodium hydroxide (NaOH) were found to be present in all by-products. By-products generated from methanol rinses were shown to contain 21 mono-oxygenated groups with no di-oxygenated moieties, the only sample encountered during investigations of fullerene-based materials containing no di-oxygenated surface groups.