Synthesis, characterization of copper oxide-gold nanoalloys and their peroxidase-like activity towards colorimetric detection of hydrogen peroxide and glucose.

Bimetallic copper oxide-gold nanoalloys (CuO-Au nanoalloys) have been prepared and characterized using various techniques confirming their successful synthesis. The peroxidase-like activity of CuO-Au nanoalloys have been investigated and applied towards the colorimetric detection of glucose. CuO-Au nanoalloys as nanoenzymes exhibited peroxidase-like properties which occurred by generating the reactive oxygen species (ROS) due to the catalytic properties of CuO-Au nanoalloys.The generation of ROS was confirmed using radical and/or reactive oxygen species quenching properties of 1,3‑diphenylisobenzofuran (DPBF). The rate of production of ROS was higher when CuO-Au nanoalloys were present in a solution containing DPBF and H ₂ O ₂ (0.1092 min ^-1 ). The absorption peak of DPBF at 430 nm decreased confirming the generation of ROS. The CuO-Au nanoalloys were evaluated their potential use for colorimetric detection of glucose. The detection limit for glucose was obtained to be 6.75 μM. The detection of glucose took place in two steps and at different pH conditions, first glucose oxidation by glucose oxidase occurred in physiological pH (7.4) at 37 °C. The optimum conditions for the CuO-Au nanoalloys peroxidase-like activity were obtained at pH 4 and 25 °C. The chromogen, TMB (3,3',5,5'‑tetramethylbenzidine) oxidation to blue coloured product TMBDI (3,5,3',5'‑tetrabenzidinediimine) occurred with high intensity obtained after 6 min.
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