Dual-active-site Fe/Cu single-atom nanozymes with multifunctional specific peroxidase-like properties for S2− detection and dye degradation

Designing single-atom nanozymes with densely exposed metal atom active sites and enhancing catalytic activity to detect pollutants remain a serious challenge. Herein, we reported a single-atom nanozyme with layered stacked Fe/Cu dual active sites (Fe/Cu-NC SAzyme) synthesized via hydrothermal and high-temperature pyrolysis using folic acid as a template. Compared with Fe-NC and Cu-NC SAzyme, Fe/Cu-NC SAzyme has higher peroxidase-like activity, which indicates that the doping of synthesized Fe/Cu bimetals can improve the catalytic activity and that the atomic loading of Fe and Cu in Fe/Cu-NC is 5.5 wt% and 2.27 wt%, respectively. When S2− is added to the Fe/Cu-NC catalytic system, a high-sensitivity and high-selectivity S2− colorimetric sensing platform can be established, with a wide linear range (0.09–6 µmol/L) and a low detection limit (30 nmol/L), which can be used to detect S2− in environmental water samples. What's more, the Fe/Cu-NC SAzyme can activate peroxymonosulfate (PMS) to degrade 99.9% of rhodamine B (RhB) within 10 min with a degradation kinetics of 0.5943 min−1. This work details attractive applications in Fe/Cu-NC SAzyme colorimetric sensing and dye degradation.