Figure 2.

Optimization of catalytic activity. A) Time-dependent absorbance of CeO₂ nanozymes doped with different metal elements at 630 nm in TMB method. B) POD-like activity of CeO₂ nanozymes doped with different metal elements. C) Time-dependent absorbance of Cr/CeO₂ nanozymes with different doping ratios at 630 nm in TMB method. D) POD-like activity of Cr/CeO₂ nanozyme with different doping ratios. Deionized water serves as blank control in all assay, marked as "con". The velocity (v) of the reaction was measured by steady-state kinetic assay using 50 μg/mL Cr/CeO₂ nanozyme. E) The concentration of TMB was 0.8 mM and varied concentration of H₂O₂. F) The concentration of H₂O₂ was 50 mM and varied concentration of TMB. Inset: Double-reciprocal plots of activity of Cr/CeO₂ nanozyme at a fixed concentration of one substrate versus varying concentration of the second substrate.