Nanoceria dissolution at acidic pH by breaking off the catalytic loop

Area of Science:

• Nanotechnology
• Materials Science
• Chemistry

Background:

• Cerium oxide nanoparticles (nanoceria) exhibit multi-enzyme-mimetic properties at neutral/high pH.
• The behavior of nanoceria as a chemical reagent at acidic pH is less understood.
• Understanding nanoceria's redox behavior is crucial for its application.

Purpose of the Study:

• To demonstrate the reproducibility and robustness of nanoceria as an oxidizing reagent at acidic pH.
• To elucidate the mechanism of nanoceria dissolution and Ce3+ release in acidic conditions.
• To develop a rapid assessment method for nanoceria's oxidative capacity.

Main Methods:

• Investigated nanoceria's chemical reactivity at acidic pH.
• Analyzed the transformation of insoluble Ce4+ to soluble Ce3+ within dissolving nanocrystals.
• Utilized titration with ferrocyanide to quantify the Ce3+/Ce4+ ratio.

Main Results:

• Nanoceria functions as a stoichiometric reagent at acidic pH, unlike its enzyme-mimetic role at other pH values.
• Insoluble Ce4+ in nanoceria converts to soluble Ce3+ and the nanocrystal dissolves.
• A titration method using ferrocyanide accurately estimates the Ce3+/Ce4+ ratio in nanoceria.

Conclusions:

• Nanoceria's behavior at acidic pH is reproducible and robust, acting as a stoichiometric reagent.
• The dissolution and Ce3+ release mechanism provides insights into its chemical reactivity.
• The ferrocyanide titration offers a rapid tool for assessing nanoceria's capacity in solution.