Fig. 4: Catalytic pathways and mechanisms of nanozymes.
a HRP mediates the peroxidation of the reducing substrate (AH2) by catalyzing H2O2 to generate FeIV=O intermediates in the active center of iron porphyrin. b Fe3O4 nanozymes mediate the peroxidase-like reaction by catalyzing H2O2 to generate free or adsorbed •OH through surface-confined FeII, which differs from HRP. c Fe3O4 nanozymes regenerate surface FeII for peroxidase-like catalysis by transferring electrons from internal FeII to the surface, during which Fe3O4 gradually depletes its activity and transforms into γ-Fe2O3. Figure adapted from Dong et al.53. d Prussian blue (PB) nanozymes may have two electron transfer pathways in the peroxidase-like catalysis process: the conduction band (CB)-mediated pathway, where PB first obtains electrons from the reducing substrate, or the valence band (VB)-mediated pathway, where PB first donates electrons to H2O2. Figure adapted from Feng et al.119. e The dominant electron pathway is determined by whether the energy level of the CB or VB is between the energy levels of H2O2 and the reducing substrate. Figure adapted from Feng et al.119. ABTS, 2,2′-azinobis-(3-ethylbenzthiazoline-6-sulfonate).
