From radicals destabilization to stable fullerenol nanoaggregates

Fullerenols are fullerenes derivatives enriched on hydroxyl groups that are obtained usually as nanoaggregates dispersed in water. These materials are used in energy-related and biological applications, and they have been reported as radical scavengers, antioxidants and stable radicals. However, most syntheses demand highly toxic solvents to dissolve precursor fullerene, potentially dangerous reagents such as hydrogen peroxide, and prolonged reactions. Herein, a novel and faster procedure for fullerenol preparation based on the reaction between fullerene C-60 and potassium hydroxide in a polar solvent is reported. Initially, fullerenol radicals are formed, followed by air oxidation that promotes charge loss and simultaneous clustering into nanoaggregates with diameters up to 90 nm. Dried fullerenol has about 12 oxygenated groups per C-60. Then, an aqueous dispersion was prepared with dispersed material having lyophobic behavior but maintaining the modification degree. This low-modified fullerenol remains dispersed indefinitely in organic medium due to electrostatic and solvation colloidal interactions arising from the functional groups. As a result, stable organic dispersions with concentrations up to 10 mg mL(-1) were obtained. This work opens new possibilities on fullerenol preparation and new perspectives concerning the achievement of stable colloids of carbon nanomaterials due to the unprecedented stability and mass concentration of the reported fullerenol dispersions. (C) 2022 The Authors. Published by Elsevier Ltd. This is an open access article under the CC BY-NC-ND license (http://creativecommons.org/licenses/by-nc-nd/4.0/)

Automated summary

This study reports a novel method for the preparation of fullerenol based on the reaction between fullerene C-60 and potassium hydroxide in a polar solvent. Fullerenol radicals are initially formed, followed by air oxidation to promote charge loss and clustering into nanoaggregates. The prepared fullerenol can be stably dispersed in an organic medium, opening up new possibilities for the preparation of stable colloids of carbon nanomaterials.