ZnO–CuxO/polypyrrole nanocomposite modified electrode for simultaneous determination of ascorbic acid, dopamine, and uric acid

Novel zinc oxide (ZnO) nanosheets and copper oxide (CuxO, CuO, and Cu2O) decorated polypyrrole (PPy) nanofibers (ZnO–CuxO–PPy) have been successfully fabricated for the simultaneous determination of ascorbic acid (AA), dopamine (DA), and uric acid (UA). The morphology and structure of ZnO–CuxO–PPy nanocomposites were characterized by scanning electron microscopy (SEM), X-ray diffraction (XRD), and Raman spectroscopy. Compared with the bare glassy carbon electrode (GCE), PPy/GCE, CuxO–PPy/GCE, and ZnO–PPy/GCE, ZnO–CuxO–PPy/GCE exhibits much higher electrocatalytic activities toward the oxidation of AA, DA, and UA with increasing peak currents and decreasing oxidation overpotentials. Cyclic voltammetry (CV) results show that AA, DA, and UA could be detected selectively and sensitively at ZnO–CuxO–PPy/GCE with peak-to-peak separation of 150 and 154 mV for AA–DA and DA–UA, respectively. The calibration curves for AA, DA, and UA were obtained in the ranges of 0.2 to 1.0 mM, 0.1 to 130.0 μM, and 0.5 to 70.0 μM, respectively. The lowest detection limits (signal/noise = 3) were 25.0, 0.04, and 0.2 μM for AA, DA, and UA, respectively. With good selectivity and sensitivity, the current method was applied to the determination of DA in injectable medicine and UA in urine samples.