Modulating the peroxidase-like activity of Fe single-atom nanozymes via atomic-scale inter-site distance engineering

Developing single-atom nanozymes (SAzymes) with neighboring metal atom active centers composed of homogeneous metal atoms and precisely regulating the distance of atom pair is still purposeful but challenging. Herein, we report an atomic-scale inter-site distance engineering for rationally designing Fe-SAzymes by regulating the inter-site distance of Fe active centers. The resulting Fe-SAzymes displayed enhanced and tunable peroxidase-like activity and Michaelis-Menten kinetics. Among FeN₄-SAzyme, Fe₂N₈-SAzyme, Fe₂N₇-SAzyme and Fe₂N₆-SAzyme configurations, the Fe₂N₇-SAzyme demonstrates exceptional specific activity (24.72 U mg^-1). Meanwhile, the density functional theory (DFT) calculations revealed that Fe₂N₇-SAzyme exhibited a higher performance of peroxidase-like catalytic activity than Fe₂N₆-SAzyme attributed to the strong electron donor ability the neighboring Fe active atom and approaching Fermi level of electronic structure. Furthermore, the resultant Fe₂N₇-SAzyme is capable of pesticide detection under low concentrations (2-10 mg L^-1), which reached the limit of detection to 0.72 mg L^-1 of malathion molecules. This work contributes to the rational design and regulation strategy for enhancing the peroxidase-like catalytic activity of SAzymes via atomic-scale inter-site distance engineering.