Limitations of Self-Regenerative Antioxidant Ability of Nanoceria Imposed by Oxygen Diffusion

Nanoceria (CeO 2– x ) is a unique antioxidant material with the ability to self-regenerate its properties after interaction with oxidants. In our paper, the dynamics of nanoceria–oxidant interaction accompanied by reversible Ce 3+ ↔ Ce 4+ transitions of cerium ions was studied for nanoceria water colloidal solutions using conventional spectroscopic techniques. We have shown that interaction of nanoceria with hydrogen peroxide leads to Ce 3+ → Ce 4+ oxidation, accompanied by quenching of Ce 3+ luminescence of nanoceria, and the recovery of initial Ce 3+ luminescence intensity occurs with a sufficient time delay (up to few days). The role of oxygen transport within ceria nanoparticles in the regeneration of antioxidant properties of nanoceria after interaction with an oxidant is discussed. Involvement of oxygen diffusion into recovery of nanoceria antioxidant properties hampers the redox activity of ceria nanoparticles making it size- and temperature-dependent.