A Detailed Insight into the Effects of Morphologies of Cerium Oxide on Fenton-like Reactions for Different...

As an exceptional Fenton-like reagent, cerium oxide (CeO₂ ) finds applications in biomedical science and organic pollutants treatment. The Fenton-like reaction catalyzed by CeO₂ typically encompasses two distinct processes: one resembling the classical Fenton reaction, wherein cerium (Ce³⁺ ) triggers the decomposition of hydrogen peroxide (H₂ O₂ ) to yield reactive oxygen species (ROS), and the other involves the complexation of H₂ O₂ on the Ce³⁺ surface, leading to the formation of peroxides. However, the influence of diverse CeO₂ morphologies on these two reaction pathways has not been comprehensively explored. In this study, CeO₂ exhibiting three typical morphologies, rods, cubes, and spheres, were prepared. The generation of ROS and peroxides was evaluated using the 3,3,5,5-tetramethylbenzidine (TMB) oxidation reaction and the reduction current of H₂ O₂ , respectively. Moreover, the impacts of pH variations and CeO₂ /H₂ O₂ concentrations on the production and conversion of these two reaction products were investigated. To corroborate the distinctions between the resultant products and their applicability, apoptosis assays and acid orange 7 (AO7) degradation analyses were performed. Notably, CeO₂ rods exhibited the highest proportion of Ce³⁺ , predominantly engaging in complexation with H₂ O₂ to foster peroxide formation, thereby facilitating the robust degradation of AO7. However, the generated peroxides appeared to occupy Ce³⁺ sites, thereby impeding the H₂ O₂ decomposition process. Conversely, Ce³⁺ species on the surface of CeO₂ cubes were primarily involved in H₂ O₂ decomposition, leading to heightened ROS production, and thus showcasing substantial potential for damaging A549 tumor cells. It is worth noting that the ability of these Ce³⁺ species to form peroxides through complexation with H₂ O₂ was comparatively reduced. In summation, this study sheds light on the intricate interplay between distinct CeO₂ morphologies and their divergent impacts on Fenton-like reactions. These findings expand our comprehension of the influences on its reactivity of CeO₂ morphologies and open new insights for applications in diverse domains, from organic dye degradation to tumor therapy.