Fine-Tuning Pyridinic Nitrogen in Nitrogen-Doped Porous Carbon Nanostructures for Boosted Peroxidase-Like Activity and Sensitive Biosensing

Carbon materials have been widely used as nanozymes in bioapplications, attributing to their intrinsic enzyme-like activities. Nitrogen (N)-doping has been explored as a promising way to improve the activity of carbon material-based nanozymes (CMNs). However, hindered by the intricate N dopants, the real active site of N-doped CMNs (N-CMNs) has been rarely investigated, which subsequently retards the further progress of high-performance N-CMNs. Here, a series of porous N-CMNs with well-controlled N dopants were synthesized, of which the intrinsic peroxidase (POD)like activity has a positive correlation with the pyridinic N content. Density functional theory calculations also reveal that pyridinic N boosts the intrinsic POD-like activity of N-CMNs. Pyridinic-N dopant can effectively promote the first H 2 O desorption process in comparison with the graphitic and pyrrolic N, which is the key endothermic reaction during the catalytic process. Then, utilizing the optimized nanozymes with high pyridinic N content (N P -CMNs) and superior POD-like activity, a facile total antioxidant capacity (TAC) assay was developed, holding great promise in the quality assessment of medicine tablets and antioxidant food for healthcare and healthy diet.