Preparation and Application of Mediator‐Free H2O2 Biosensors of Graphene‐Fe3O4 Composites

Abstract

Graphene‐Fe₃O₄ (G‐Fe₃O₄) composites were prepared with a solvothermal method for the immobilization of horseradish peroxidase (HRP) to construct a mediator‐free H₂O₂ biosensor. The morphology and structure of the G‐Fe₃O₄ composites were analyzed by TEM, SEM, and XRD. Chitosan (CH) was utilized to disperse the composites, and the mixture of CH, G‐Fe₃O₄ and HRP was spin‐coated on an indium tin oxide (ITO) electrode to form a biocomposites film. Electrochemical impedance spectroscopy (EIS) and cyclic voltammograms (CV) demonstrated the fast electron transfer process between HRP and the electrode. The resulted H₂O₂ biosensor exhibited a rapid response upon the addition of H₂O₂, a high sensitivity of 132 µA mM⁻¹ cm⁻² and a low detection limit of 6×10⁻⁷ M. The linear range of the biosensor is from 5×10⁻⁶ to 3.81×10⁻³ M (r=0.997). Such interesting G‐Fe₃O₄ composites with easy preparation and low cost can provide a novel matrix for enzyme immobilization to construct biosensors with higher performance.