A novel hydrogen peroxide biosensor based on Au-graphene-HRP-chitosan biocomposites

Graphene was prepared successfully by introducing -SO₃⁻ to separate the individual sheets. TEM, EDS and Raman spectroscopy were utilized to characterize the morphology and composition of graphene oxide and graphene. To construct the H₂O₂ biosensor, graphene and horseradish peroxidase (HRP) were co-immobilized into biocompatible polymer chitosan (CS), then a glassy carbon electrode (GCE) was modified by the biocomposite, followed by electrodeposition of Au nanoparticles on the surface to fabricate Au/graphene/HRP/CS/GCE. Cyclic voltammetry demonstrated that the direct electron transfer of HRP was realized, and the biosensor had an excellent performance in terms of electrocatalytic reduction towards H₂O₂. The biosensor showed high sensitivity and fast response upon the addition of H₂O₂, under the conditions of pH 6.5, potential −0.3 V. The time to reach the stable-state current was less than 3 s, and the linear range to H₂O₂ was from 5 × 10⁻⁶ M to 5.13 × 10⁻³ M with a detection limit of 1.7 × 10⁻⁶ M (S/N = 3). Moreover, the biosensor exhibited good reproducibility and long-term stability.