Growth of CuO nanoneedles on graphene quantum dots as peroxidase mimics for sensitive colorimetric detection of hydrogen peroxide and glucose

Graphene quantum dots-copper oxide nanocomposites (GQDs/CuO) are facilely fabricated by the growth of CuO nanoneedles on graphene quantum dots under mild conditions. The as-prepared GQDs/CuO nanocomposites could be used as an effective peroxidase mimics to catalyze the oxidation of 3,3′,5,5′-tetramethylbenzidine (TMB) in the presence of H2O2 to produce a blue-colored solution. Investigations on the mechanism indicate that the nature of peroxidase-like activity of GQDs/CuO nanocomposites originates from OH radical generation. The increase of absorbance at 652 nm induced by the catalytic effect of GQDs/CuO nanocomposites offers accurate detection of H2O2 in the range of 0.5-10 μM, along with a detection limit of 0.17 μM. A colorimetric method for serum glucose detection is also proposed by combining the GQDs/CuO catalytic reaction and the enzymatic oxidation of glucose with glucose oxidase. This method is simple, sensitive and selective for glucose detection with a linear range from 2 to 100 μM with a detection limit of 0.59 μM.