Superoxide ion (O2−) adsorption on C20 fullerene: A DFT study for antioxidant material design

Oxidative stress drives the search for advanced antioxidant nanomaterials. This study evaluates the smallest fullerene, C 20 , as an efficient scavenger of the superoxide radical (O 2 − ). Density Functional Theory (DFT) calculations, including implicit solvation effects, reveal that the Jahn-Teller instability of C 20 creates a highly reactive surface with localized electrophilic sites that facilitate radical neutralization. O 2 − adsorbs on the C 20 surface through covalent chemisorption and charge-transfer physisorption, which are thermodynamically spontaneous in gas and aqueous phases. These interactions reduce the system's electrophilicity by approximately 99% of pristine C 20 and result in electronically stabilized complexes. Topological analyses indicate shared-shell characteristics consistent with a chemical adsorption pathway. Time-dependent DFT predicts visible/NIR charge-transfer signatures for the physisorbed complexes, opening possibilities for non-invasive radical sensing. Although solvation decreases the adsorption energies, the process remains spontaneous in water, supporting the biological feasibility of C 20 as a next-generation antioxidant and biosensing platform.