Engineering Nanoceria for Enhanced Peroxidase Mimics: A Solid Solution Strategy

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: Mn1Ce10 > Co1Ce10 > Fe1Ce10 > Cu1Ce10 > CeO2 > Ni1Ce10. By further varying the Mn/Ce ratio, Mn1Ce5 with the highest peroxidase mimicking activity was obtained (13-fold higher compared with the pristine CeO2). Meanwhile we found that the homogenous doping of Mn into the nanoceria matrix without phase segregation ensured the formation of Mn1Ce5 solid solution. From our experiments and discussion, we concluded that the surface oxygen (O-beta) and the synergistic effect between Ce and Mn played key roles in the enhancement of Mn1Ce5 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.