A Facile synthesis of superparamagnetic Fe3O4 nanofibers with superior peroxidase-like catalytic activity for sensitive colorimetric detection of L-cysteine

Superaramagnetic Fe₃O₄ nanomaterials are good candidates as enzyme mimics due to their excellent catalytic activity, high stability and facile synthesis. However, the morphology of Fe₃O₄ nanomaterials has much influence on their enzyme-like catalytic activity. In this work, we have developed a simple polymer-assisted thermochemical reduction approach to prepare Fe₃O₄ nanofibers for peroxidase-like catalytic applications. The as-prepared Fe₃O₄ nanofibers show a higher catalytic activity than commercial Fe₃O₄ nanoparticles. The steady-state kinetic assay result shows that the Michaelis-Menten constant value of the as-obtained Fe₃O₄ nanofibers is similar to that of horseradish peroxidase (HRP), indicating their superior affinity to the 3,3‧,5,5‧-tetramethylbenzidine (TMB) and H₂O₂ substrate. Based on the outstanding catalytic activity, a sensing platform for the detection of L-cysteine has been performed and the limit of detection is as low as 0.028 μM. In addition, an excellent selectivity toward L-cysteine over other types of amino acids, glucose and metal ions has been achieved as well. This work offers an original means for the fabrication of superparamagnetic Fe₃O₄ nanofibers and demonstrates their delightful potential applications in the fields of biosensing, environmental monitoring, and medical diagnostics.