A facile synthesis of Fe ₃ O ₄ /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 nanofibers, 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 α-Fe₂O₃ nanofibers under hydrothermal reaction using α-Fe₂O₃ nanofibers as both a template and an oxidant. Then the prepared α-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 α-Fe₂O₃ nanofibers, α-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 μM and a detection limit of 0.04 μM 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.