A facile synthesis of Fe3O4/nitrogen-doped carbon hybrid nanofibers as a robust peroxidase-like catalyst for the sensitive colorimetric detection of ascorbic acid

In recent years, the fabrication of functional nanostructures with multicomponents for a variety of novel biosensors has received considerable attention due to their synergistic improved sensitivity. Herein, we report a facile approach for the preparation of Fe3O4/nitrogen-doped carbon (Fe3O4/N-C) hybrid nano-fibers, and construct a sensing platform for the sensitive colorimetric detection of H2O2 and ascorbic acid (AA). During the synthetic process, a discontinuous layer of polypyrrole (PPy) is first polymerized in situ on the surface of the alpha-Fe2O3 nanofibers under hydrothermal reaction using alpha-Fe2O3 nanofibers as both a template and an oxidant. Then the prepared alpha-Fe2O3/PPy nanofibers are converted into Fe3O4/N-C hybrid nanofibers through pyrolysis with a thermochemical reduction process. The resulting Fe3O4/N-C hybrid nanofibers are used as a novel peroxidase mimic towards the oxidation of 3,3,5,5-tetramethylbenzidine (TMB) in the presence of H2O2, with a superior catalytic activity over individual alpha-Fe2O3 nanofibers, alpha-Fe2O3/PPy nanofibers, Fe3O4/C nanofibers, and commercial Fe3O4 nanoparticles. Based on the high peroxidase-like activity of Fe3O4/N-C hybrid nanofibers, a sensing platform for the colorimetric detection of AA is developed. A good linear relationship from 0 to 50 mM and a detection limit of 0.04 mM are achieved. This work offers a new method for the preparation of Fe3O4/N-C hybrid nanofibers and presents new potential applications in biosensing, medical diagnostics and environmental monitoring.