Synthesis of well-dispersed Fe3O4 nanoparticles loaded on montmorillonite and sensitive colorimetric detection of H2O2 based on its peroxidase-like activity

Abstract

In this study, a simple strategy for the preparation of Fe₃O₄ nanoparticles (NPs) loaded on montmorillonite as a support is reported. The Fe₃O₄–MMT nanocomposites (NCs) were demonstrated to possess peroxidase-like activity and could catalyze the oxidation of 3,3′,5,5′-tetramethylbenzidine (TMB) to a blue oxidation product (oxTMB) in the presence of hydrogen peroxide. The obvious color change can be used to quantify the H₂O₂ concentration using UV-vis spectroscopy. In addition, the Fe₃O₄–MMT NCs exhibit enhanced peroxidase-like activity as compared to MMT or pure Fe₃O₄ NPs. Steady-state kinetics studies and a hydroxyl radical detecting assay were carried out to investigate the peroxidase-like activity and catalytic mechanism of these NCs. Under the optimized conditions, Fe₃O₄–MMT NCs are expected to be used as a good colorimetric biosensor for the detection of H₂O₂, which have a linear range from 5 × 10⁻⁵ M to 2 × 10⁻⁴ M with a detectable H₂O₂ concentration as low as 5.1 × 10⁻⁶ M. This sensor was also successfully applied to detect H₂O₂ in contact lens solution samples.