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

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.