Mechanical transformation of fullerene (C₆₀) to aqueous nano-C₆₀ (aqu-nC₆₀) in the presence and absence of light

The present study was carried out to evaluate transformation kinetics of derivatized fullerene species by simulating natural aquatic processes, which will help elucidate biological effects of water-stirred nano-C₆₀ (aqu-nC₆₀). Physicochemical analyses of aqu-nC₆₀ included molecular and agglomerate-scale characterization, surface charge analysis through examination of electrophoretic mobility, and chemical composition analysis using spectroscopy. Detailed analysis of aqu-nC₆₀ transformation over a 28-day stirring period in both light and dark conditions indicated aqu-nC₆₀ agglomerate concentrations can be estimated as a time-function using a predictor model (R ² > 0.99). Number-weighted agglomerate size did not differ significantly over the 28-day stirring period regardless of photocondition, although size distributions were more uniform as stirring time increased. The total number of surface groups identified through XPS indicated increased derivatization as a function of time with additions assigned to mono-oxygenated carbon moieties while the number of di-oxygenated moieties declined. Earlier-phase stirring (t ≤ 14 days) products were shown to contain epoxide surface groups, which were absent in later-phase (t > 14 days) suspensions, suggesting specific pathways to derivatization with preferential mono-oxygenated states. Filter residue, a by-product of the aqu-nC₆₀ synthesis process, demonstrated high hydrophobicity and FTIR spectra similar to underivatized material, suggesting synthesis process inefficiencies.