Antioxidant properties of ALD grown nanoceria films with tunable valency

Herein, we provide the first account of a method to control cerium oxide's mixed valence states (as Ce3+ to Ce4+ ratio) in ultra-thin films formed via atomic layer deposition (ALD). It is determined that modulation of Ce3+/Ce4+ ratio occurs with respect to film thickness and is analogous to the change in surface chemistry observed for cerium oxide nanoparticles with varying particle diameter. The influence of film thickness on enzyme-mimetic radical scavenging is also characterized. Higher film thicknesses show 9-fold increase in catalytic activity. In vitro biocompatibility (apoptosis < 4%) and electrochemical biosensing (lowest concentration: 18 ppt) studies were performed to demonstrate the potential of ALD-grown nanoceria films for biomedical applications.