Quasi-equilibrium distribution of pristine fullerenes C60 and C70 in a water–toluene system

Abstract

An improved technique of the ultrasound-assisted reversible liquid–liquid transfer of pristine (unmodified) C60 and C70 fullerenes between organic solutions and aqueous fullerene dispersions (AFD; another notation in general use, nC60, nC70) without any additional reagents (media modifiers) was developed. To our knowledge, this is the first report of such a fullerene transfer from an AFD to an organic phase. Based on the observation of this fullerene reversible transfer, their distribution between the aqueous and organic phases was considered. A quasi-equilibrium transfer mechanism was proposed, which makes it possible to estimate distribution constants, KD, as 6 and 2, for C60 and C70 respectively, in a water–toluene system. Under the optimum conditions, AFDs of C60 and C70 with the concentrations 180 ± 20 and 70 ± 20 μM, respectively, were obtained from the corresponding solutions in toluene. Based on UV/vis spectroscopy, total organic carbon, headspace GC–MS, and MALDI measurements, a reliable analytical procedure to measure fullerene concentrations and to monitor the concentration of residual toluene in AFDs was proposed. AFDs of a mixture of fullerenes C60 and C70 were characterized by the developed technique.