Immobilization of hemoglobin on functionalized multi-walled carbon nanotubes-poly-l-histidine-zinc oxide nanocomposites toward the detection of bromate and H2O2

•Simple and eco-friendly strategy for the preparation of f-MWCNT–P-l-His–ZnO and Hb/f-MWCNT–P-l-His–ZnO composite.•It offered good selectivity, stability, reproducibility with a wide linear range and low LOD.•The proposed biosensor was applied to detect H2O2 and bromate in real samples. A novel biocompatible sensing strategy has been developed based on functionalized multi-walled carbon nanotube (f-MWCNT), poly-l-histine (P-l-His), and ZnO nanocomposite film for the immobilization of hemoglobin (Hb). The direct electron transfer properties and bioelectrocatalytic activity of the Hb in f-MWCNT–P-l-His–ZnO composite film is further investigated. The apparent heterogeneous electron transfer rate constant (ks) of Hb confined to f-MWCNT–P-l-His–ZnO nanocomposite is found to be 5.16s−1 using Laviron's equation. Moreover, the surface coverage concentration (Γ) of the electroactive Hb in the f-MWCNT–P-l-His–ZnO film is estimated to be 1.88×10−9molcm−2. The fabricated electrochemical biosensor based on the immobilized Hb revealed a fast response time (