Single-atom iron confined within polypyrrole-derived carbon nanotubes with exceptional peroxidase-like activity for total antioxidant capacity

Single-atom catalysts possess the advantages of robustness, maximum atomic utilization, and low cost, offering an efficient strategy to remarkably promote the catalytic performance of nanozymes. Herein, high-efficiency and durable Fe-N-doped carbon nanotubes (Fe-NC NTs) for enzyme mimicking are synthesized through a simple in-situ polymerization and subsequent pyrolysis process derived from polypyrrole (PPy) without additional acid etching treatment. The distinct tubular structure provides abundant accessible active sites and fast electron/mass transport, benefitting for the improved catalytic activity. Compared to commercial Fe3O4 nanoparticles, the Fe-NC NTs show an unprecedented peroxidase-like activity. Then we develop a simple colorimetric assay to detect H2O2 and ascorbic acid (AA) with a high sensitivity. Furthermore, the total antioxidant capacity (TAC) sensor for a series of real samples is constructed, which has been verified by a conventional cupric reducing antioxidant capacity (CUPRAC) strategy, demonstrating the reliability of the demonstrated peroxidase-like reaction. The high activity of tubular single-atom catalysts offers new insight to design high-performance nanozymes for promising sensing and exogenous dietary and healthcare applications.