Hydrogen peroxide biosensor based on chitosan/2D layered double hydroxide composite for the determination of H₂O₂

The composites (LDH-CMC) composed of carboxymethyl chitosan (CMC) and 2D ZnAl layered double hydroxide (LDH) were successfully prepared using the one-step urea method; these composites were characterized by XRD, FT-IR, UV-vis DRS, SEM, BJH/BET, TG-DTG and pH_zpc analyses, cyclic voltammetry, and electrochemical impedance spectroscopy. The use of CMC could impact the textural and surface chemical properties of the LDH-CMC composites, where the composites still maintained the 2D layered structure. Incorporating a moderate amount of CMC could increase both the surface area and the permanent charge density of the composites, leading to improved electrochemical performances. The LDH-CMC composite was used as a support matrix for the immobilization of horseradish peroxidase (HRP) on the glass carbon (GC) electrode to construct a biosensor that provides a biocompatible microenvironment for HRP and a pathway for H₂O₂ diffusion via the high surface area. The HRP biosensor displayed a satisfactory sensitivity and fast response (<3 s) toward H₂O₂ over a wide linear range of 0.02-6.0 mmol·L^-1 with a low detection limit of 12.4 μmol·L^-1, good anti-interference ability and long-term storage stability. The proposed HRP biosensor was found to be a sensitive, rapid, and disposable sensor with low cost, easy preparation and high selectivity; thus, the proposed biosensor can be used for the real-time detection of trace H₂O₂ in the biological, clinical and environmental fields.