S‐Doping Regulated Iron Spin States in Fe−N−C Single‐Atom Material for Enhanced Peroxidase‐Mimicking Activity at Neutral pH

Abstract

Designing biomimetic nanomaterials with peroxidase (POD)-like activity at neutral pH remains a significant challenge. An S-doping strategy is developed to afford an iron single-atom nanomaterial (Fe₁@CN-S) with high POD-like activity under neutral conditions. To the best of knowledge, there is the first example on the achievement of excellent POD-like activity under neutral conditions by regulating the active site structure. S-doping not only promotes the dissociation of the N─H bond in 3,3″,5,5″-tetramethylbenzidine (TMB), but also facilitates the desorption of OH* by the transformation of iron species' spin states from middle-spin (MS Fe^II) to low-spin (LS Fe^II). Meanwhile, LS Fe^II sites typically have more unfilled d orbitals, thereby exhibiting stronger interactions with H₂O₂ than MS Fe^II, which can enhance POD-like activity. Finally, a one-pot visual detection of glucose at pH 7 is performed, demonstrating the best selectivity and sensitivity than previous reports.