Highly stable biomolecule supported by gold nanoparticles/graphene nanocomposite as a sensing platform for H₂O₂...

A highly active and stable composite of hemin (HN) supported by reduced graphene oxide/gold nanoparticles (HN-RGO/AuNPs) was prepared by one-pot hydrothermal method. The physicochemical properties of the as-prepared composites were characterized by field emission scanning electron microscopy (FESEM), transmission electron microscopy (TEM), UV-vis spectroscopy, Raman spectroscopy and X-ray diffraction technique (XRD). The HN-RGO/AuNP-modified electrode shows a stable and well-defined, surface-confined redox couple at an apparent formal potential of -0.317 V vs. Ag|AgCl with a surface coverage value of 2.239 × 10^-10 mol cm^-2. Compared with HN, HN-GO and HN-RGO, the HN-RGO/AuNP-modified electrode exhibits excellent electrocatalytic activity towards hydrogen peroxide (H₂O₂). Under optimum conditions, the HN-RGO/AuNP-modified electrode shows a wide linear response ranges from 0.05 μM to 518.15 μM towards H₂O₂ with a fast response time (3 s). The calculated sensitivity and limit of detection (LOD) of the biosensor were 3.99 μA μM^-1 cm^-2 and 16 nM, respectively. In addition, the Michaelis-Menten constant value of the biosensor is 0.13 mM, which indicates the high affinity of HN towards the reduction of H₂O₂. The proposed biosensor displays high sensitivity and selectivity towards H₂O₂ in the presence of common biologically co-existing species. The biosensor shows an acceptable practical ability in human serum, contact lens solution and milk samples with an appreciable recovery.