A colorimetric strategy for ascorbic acid sensing based on the peroxidase-like activity of core-shell Fe3O4/CoFe-LDH hybrid.

A novel core-shell Fe3O4/CoFe-LDH (layered double hydroxides) hybrid as a peroxidase mimic for the colorimetric detection of ascorbic acid was first fabricated via a facile two-step route. The resulting Fe3O4/CoFe-LDH hybrid exhibited much higher peroxidase-like catalytic activity for the oxidation of 3,3',5,5'- tetramethylbenzidine (TMB) with H2O2 than the pristine Fe3O4 and CoFe-LDH nanosheets owing to the unique hierarchical architecture containing more exposed active sites and the synergistic effect between Fe3O4 and CoFe-LDH. A sensitively and selectively visual sensor for the determination of ascorbic acid (AA) was successfully constructed based on the reduction effect of AA with enediol group on the formed oxidation of TMB, which exhibited a sensitive response to AA in the range of 0.5 ∼ 10 μM with the detection limit of 0.2 μM. Additionally, the Fe3O4/CoFe-LDH magnetic hybrid could be easily recycled by applying a magnetic field. This work provided a feasible means for the fabrication of magnetic nanomaterials with encouraging prospect in biosensing, environmental monitoring and medical diagnostics.