Prussian blue with intrinsic heme-like structure as peroxidase mimic

Despite the intrinsic peroxidase-like activity of Prussian blue nanoparticles (PBNPs), their enzyme-mimic mechanism has been scarcely investigated to date. Herein, we probed the catalytic site of PBNPs for the first time, by comparing their peroxidase-like activity with that of a series of Prussian blue analogs (PBAs) in which Fe atoms were replaced by Co, Ni, and Cu. The PBNPs exhibited the highest maximal reaction velocity (1.941 μM·s^-1), which was at least 13 times higher than that of the PBAs, demonstrating that the peroxidase-like properties of PBNPs could be ascribed to the FeN_x (x = 4-6) instead of the FeC₆ units. Notably, the PBNPs/H₂O₂ couple also showed much higher oxidizability than ·OH radicals produced from the Fenton reaction, implying that a high active Fe(Ⅳ)=O intermediate might be formed in the FeN_x units. This study can thus pave the way for the wider application of PBNPs in biomimetic reactions.