Synergistic Fe-Mo Dual Single-Atom Nanozymes: Enhanced Peroxidase-Like Activity and Colorimetric Detection of...

Single-atom nanozymes have been applied in biosensing. However, their enzyme catalytic activity still needs to be further improved to meet diverse biosensing needs. Here, we develop a hollow cube (HC)-structured Fe₁Mo₁ dual single-atom nanozyme (Fe₁Mo₁-HC) with enriched N₃-Fe₁-Mo₁-N₃ active sites to boost peroxidase (POD)-like activity. Fe₁Mo₁-HC shows a higher substrate affinity (K_m = 0.44 mM for 3,3',5,5'-tetramethylbenzidine (TMB) and 25.23 mM for H₂O₂) and catalytic efficiency (k_cat/K_m = 5.18 × 10⁶ M^-1 s^-1 for TMB and 1.30 × 10⁵ M^-1 s^-1) than those of Fe₁-HC (K_m = 0.82 mM for TMB and 1098 mM for H₂O₂, k_cat/K_m = 7.24 × 10⁵ M^-1 s^-1 for TMB, and 7.64 × 10² M^-1 s^-1) and Mo₁-HC (K_m = 0.81 mM for TMB and 647 mM for H₂O₂ and k_cat/K_m = 8.60 × 10⁵ M^-1 s^-1 for TMB and 1.49 × 10³ M^-1 s^-1). Density functional theory investigations reveal that the Fe₁Mo₁-HC catalyst has two metal sites, and it overcomes the difficulty in the formation of *O,H₂O₂ for the single-atom catalysts, resulting in higher POD activity. Based on this property, we constructed a Fe₁Mo₁-HC nanozyme sensor for sensitive colorimetric detection of l-penicillamine (L-PA) with satisfactory detection results.