Electrocatalytic activity of core/shell magnetic nanocomposite

Electrically active magnetic nanocomposites (EAMNCs), Au nanoparticles/self-doped polyaniline@Fe3O4 (AuNPs/SPAN@Fe3O4) with well-defined core/shell structure, were first synthesized by a simple method. The morphology and composition of the as-synthesized AuNPs/SPAN@Fe3O4 nanocomposite have been characterized by transmission electron microscopy (TEM), scanning electron microscopy (SEM), Fourier transform infrared (FT–IR), ultraviolet–visible (UV–Vis), X-ray powder diffraction (XRD), and thermogravimetric analysis (TGA). Horseradish peroxidase (HRP)–AuNPs/SPAN@Fe3O4 biocomposites were immobilized onto the surface of indium tin oxide (ITO) electrode to construct an amperometric hydrogen peroxide (H2O2) biosensor. The effects of HRP dosage, solution pH, and the working potential on the current response toward H2O2 reduction were optimized to obtain the maximal sensitivity. Under the optimal conditions, the proposed biosensor exhibited a linear calibration response in the range of 0.05 to 0.35 mM and 0.35 to 1.85 mM, with a detection limit of 0.01 mM (signal-to-noise ratio = 3). The modified electrode could virtually eliminate the interference of ascorbic acid (AA) and uric acid (UA) during the detection of H2O2. Furthermore, the biosensor was applied to detect H2O2 concentration in real samples, which showed acceptable accuracy with the traditional potassium permanganate titration.