N, P, S Codoped Carbon Nanozymes with Enhanced Peroxidase-like Activity and Binding Affinity for Total Antioxidant Capacity Assay

Developing peroxidase-like sensors with excellent catalytic activity to construct colorimetric sensors has been an important challenge for a long time. The electronegativity of the doped nonmetallic atoms can change the chemical environment of the carbon material and promote the redistribution of electrons, thus improving the electron transfer channel between the nanozyme and the reaction substrate and further enhancing the peroxidase-like activity. Herein, a nitrogen (N), phosphorus (P), and sulfur (S) codoped carbon nanozyme (NPS-C) was successfully designed via one-step high-temperature pyrolysis. Compared with N-doped nanozymes (N–C), N and P codoped carbon nanozymes (NP-C) have a lower Michaelis–Menten constant, and N and S codoped carbon nanozymes (NS-C) have a higher reaction rate. Therefore, based on the synergy between different atoms, NPS-C exhibited excellent peroxidase-like activity and stronger substrate binding affinity, which effectively activated H2O2 to produce reactive oxygen intermediates with a stronger oxidation capacity and superoxide anion radical (•O2–) and promoted TMB to lose an electron and be oxidized to oxTMB. Moreover, ascorbic acid (AA), as an antioxidant model, can rapidly consume reactive oxygen species and reduce oxTMB. Therefore, based on the excellent peroxidase-like activity of NPS-C and the linear relationship between the concentration of AA and the inhibition degree of peroxidase-like activity, a colorimetric sensor can be constructed to analyze the total antioxidant capacity (TAC) in beverages.