Fe—N—C single atom nanozymes with dual enzyme-mimicking activities for colorimetric detection of hydrogen peroxide and glutathione

H₂O₂ and glutathione (GSH) are critical redox molecules in the organism. Abnormal levels of cellular H₂O₂ and GSH are closely related to some diseases. Thus, it is imperative to detect H₂O₂ and GSH efficiently. In this work, Fe—N—C single atom nanozymes (SANs) with both peroxidase and oxidase-mimicking activities were successfully prepared with the help of formamide condensation by one-step hydrothermal method. The Fe—N—C SANs show excellent peroxidase-like activity, which possess a higher affinity for H₂O₂ and 3, 3′, 5, 5′-tetramethylbenzidine (TMB) than horseradish peroxidase (HRP). Then, based on the chromogenic reaction of TMB, a colorimetric biosensor to detect H₂O₂ and GSH was developed. This biosensor has the linear ranges of 10–600 μmol/L for H₂O₂ with a low detection limit of 4.360 μmol/L and 100–400 μmol/L for GSH with a low detection limit of 78.33 μmol/L. Besides, this colorimetric biosensor exhibited a good recovery of H₂O₂ and GSH in diluted human serum. Finally, the Fe—N—C SANs were encapsulated into agar gel to self-quantitatively detect GSH by naked eyes. This work provides a non-pyrolytic way to prepare SANs, which broadens the synthetic method of SANs and may promote the development of SANs for biosensor application.