Naked eye detection of hydrogen peroxide via curcumin functionalised gold nanoparticles.

Nanozymes are a class of inorganic nanomaterials that mimic enzyme activity. Their high durability and strong catalytic performance make them effective surrogates for natural enzymes. In this study, we synthesized curcumin-stabilized gold nanoparticles, which were employed for the colorimetric detection of hydrogen peroxide (H₂O₂) using the chromogenic substrate 3,3',5,5'-tetramethylbenzidine (TMB). Steady-state kinetic parameters were determined by varying the substrate concentrations. When H₂O₂ was used as the substrate, the Michaelis-Menten constant (Km) and the maximum reaction rate (Vmax) were found to be 3.10 × 10⁻³ M and 9.27 × 10⁻⁷ M/s, respectively. For TMB, the Km and Vmax values were 0.30 × 10⁻³ M and 1.80 × 10⁻⁷ M/s, respectively. The lower Km value for H₂O₂ indicates a higher affinity of the nanozyme for this substrate. The electron transfer ability of the nanozyme was further confirmed by cyclic voltammetry and impedence analysis, performed by immobilizing the gold nanoparticles on the surface of an electrode. Thus, this study presents a dual-mode method for the detection of H₂O₂ using curcumin-stabilized gold nanoparticles.