Engineering Nanoceria for Enhanced Peroxidase Mimics: A Solid Solution Strategy

Graphical Mn 1 Ce 5 solid solution with the highest Mn content exhibited the highest peroxidase mimicking activity. Both the surface oxygen (O β ) and the synergistic effect between Ce and Mn played key roles in the peroxidase mimicking activity of the Mn doped nanoceria, demonstrating Mn doped nanoceria as promising peroxidase mimics and also provides an effective and facile strategy for modulating the catalytic activity of nanozymes. Nanoceria has been developed as a biocompatible and robust enzyme mimic (called ceria nanozyme) and applied in bioanalysis and therapeutics. However, its catalytic activity such as peroxidase mimic is still moderate, which in turn has limited its promising applications. To tackle this issue, herein we reported an effective strategy to modulate the peroxidase mimicking activity of nanoceria by doping transition metals. We discovered that doping of the first row of transition metals ( i. e ., Mn, Fe, Co, Ni, and Cu) modulated the activity of nanoceria and with the same doping ratio the activities followed the below order: Mn 1 Ce 10 >Co 1 Ce 10 >Fe 1 Ce 10 >Cu 1 Ce 10 >CeO 2 >Ni 1 Ce 10 . By further varying the Mn/Ce ratio, Mn 1 Ce 5 with the highest peroxidase mimicking activity was obtained (13-fold higher compared with the pristine CeO 2 ). Meanwhile we found that the homogenous doping of Mn into the nanoceria matrix without phase segregation ensured the formation of Mn 1 Ce 5 solid solution. From our experiments and discussion, we concluded that the surface oxygen (O β ) and the synergistic effect between Ce and Mn played key roles in the enhancement of Mn 1 Ce 5 peroxidase mimicking activity. This study not only demonstrates that Mn-doped nanoceria exhibits higher active peroxidase mimics but also provides a promising strategy to modulate the catalytic activity of nanozymes.