Turn-on colorimetric detection of hydroquinone based on Au/CuO nanocomposite nanozyme

CuO nanorods bearing Au nanoparticles (Au/CuO nanocomposites) were prepared by a solution-phase synthesis and exhibited efficient hydroquinone (HQ)-oxidase activity with good specificity. The Au/CuO nanocomposites effectively catalyzed the oxidation of colorless HQ to brown benzoquinone with an absorbance maximum at 376 nm but did not catalyze the conversions of catechol or resorcinol. Kinetic studies indicated that the Au/CuO nanocomposites exhibited a strong affinity for HQ, with a Michaelis–Menten constant of K m = 0.33 mM. Owing to the high catalytic activity and specificity, a strong color was observed at low concentrations of HQ. Quantitative measurement of HQ was performed via colorimetric analysis, which yielded a detection limit of 3 μM with a linear range of 5–200 μM. This colorimetric sensor was successfully applied to an HQ assay of real water samples with satisfactory results. Graphical abstract