Engineering of Oxygen-Deficient Nano-CeO_2–x with Tunable Biocidal and Antioxidant Activity

Abstract

Biocidal activity and radical scavenging capacity (RSC), two seemingly opposing concepts, can coexist in engineered nanoceria (CeO 2 ) materials. In the present study, a series of CeO 2−x (x = 0−0.75) nanoparticles have been engineered utilizing the anoxic-flame spray pyrolysis (A-FSP) technology. A-FSP allows for tuning of the physicochemical and structural properties of CeO 2−x arising from lattice defects (Ce 3+ and V os ) while maintaining minimal carbon incorporation. Our study aimed to understand the complex relationships between the biocidal and antioxidant activities of CeO 2−x , concepts whose origin was not sufficiently detangled in the bibliography. The biocide profiles of CeO 2−x nanoparticles toward the marine bacterium Aliivibrio fischeri were studied in tandem with their reactive oxygen species (ROS) scavenging capacity. A key finding of the present study is that the A-FSP process allows selective engineering of cluster-type Ce 3+ and V o defects, while typical, nonanoxic nanoceria structures (code-named ox-CeO 2 ) present mainly monomeric Ce 3+ defects. The type of Ce 3+ defects directly impacts the ROS scavenging efficiency. In addition, structural modifications that occur from the presence of cluster-type Ce 3+ defects, such as larger particle sizes, are directly associated with lower biocidal activity. Thus, the findings of this study indicate that biocidal and ROS antioxidant activities are not mutually exclusive properties.