Hydration or hydroxylation: direct synthesis of fullerenol from pristine fullerene [C60] via acoustic cavitation in the presence of hydrogen peroxide

Abstract

A green and clean approach that requires low energy and avoids the use of any toxic or corrosive reagents/solvents for the synthesis of potential fullerenol moieties [C₆₀(OH)_n·mH₂O] was proposed in this investigation, in which pristine fullerene (C₆₀) in dil. H₂O₂ (30%) aqueous media was ultrasonicated (20 kHz, 200 W) at 30% amplitude for 1 h. The attachment of hydroxyl groups (–OH) was investigated via FTIR and the quantification of –OH groups attached to the C₆₀ cage was conducted via elemental analysis. The number of secondary bound water molecules (mH₂O) with each fullerenol molecule [C₆₀(OH)_n] was measured via TGA, and the estimated average structure of fullerenol was calculated to be C₆₀(OH)₈·2H₂O. The synthesized fullerenol was moderately soluble in water and DMSO. Furthermore, the size of the synthesized C₆₀(OH)₈·2H₂O particles determined by both AFM and DLS analysis was found to be in the range of 135–155 nm. The proposed ultrasound-assisted acoustic cavitation technique encompasses a one-step facile reaction strategy, requires less time for the reaction, and reduces the number of solvents required for the separation and purification of C₆₀(OH)₈·2H₂O, which could be scalable for the commercial synthesis of fullerenol moieties in the future.