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A new nanocomposite based on ruthenium nanoparticles (RuNPs) uniformly designed at chemically treated graphene oxide nanosheets (CTGONS) was prepared as active electrode for simultaneously sensing of dopamine (DA) and acetaminophen (AC) in the presence of high concentration of ascorbic acid (AA). The RuNPs actively decorates the CTGONS with uniform dispersion like pump sputtering of paints. The CTGONS of hexagonal nanosheets, 2D orientation, chemically treated to the reduced forms and active decoration by RuNPs lead to formation of high catalytic active sites and high loading of targets at the electrode surface. The suitable accommodation of RuNPs/CTGONS to fast response of targets ascertains a high catalytic activity, and fast charge transport. The RuNPs/CTGONS nanocomposite shows an obvious catalytic oxidation signal for DA and AC. The highly sensitive and selective electrode was designed based on RuNPs/CTGONS due to the large peak potentials separation of DA to AC of 0.22 V with sufficient electron mediating behavior. Moreover, the nanocomposite electrode shows individual and simultaneous determination of DA and AC with linear calibration plots from 5–120 μM and 10–120 μM, where their detection limits were calculated to be 0.018±0.002 and 0.023±0.003 μM, respectively. Finally, the analytical application of the RuNPs/CTGONS electrode was applied for the determination of DA and AC in the serum of human blood. [ABSTRACT FROM AUTHOR]

• A novel nanocomposite based on the (Au/Ag/Pd)NPs/EPGr was fabricated. • The nanocomposite was applied for the simultaneous determination for AA, DA, AP and TP. • A high sensitive and large separation peak potentials for AA–DA, DA–AP, and AP–TP were observed. • The low limits of detection for AA, DA, AP and TP were estimated as compared to other reports. • The nanocomposite successfully applied for the determination of these species in real sample. A novel nanocomposite sensor based on trimetallic nanoparticles of (Au/Ag/Pd)NPs uniformly capped electropretreated graphene oxide (EPGrO) was fabricated. The investigation and characterization of the (Au/Ag/Pd)NPs/EPGrO nanocomposite were studied by X-ray photoelectron spectroscopy (XPS), scanning electron microscopy (SEM), transmission electron microscopy (TEM), X-ray diffraction (XRD) and energy-dispersive X-ray spectroscopy (EDX) techniques. Cyclic voltammograms (CVs) of the nanocomposite electrode displayed obvious and sharp oxidation peaks for each ascorbic acid (AA), dopamine (DA), acetaminophen (AP) and tryptophan (TP) as compared to their responses at EPGrO and bare electrodes. An efficient electron mediating behavior of the nanocomposite electrode with large separation peak potentials for AA–DA, DA–AP, and AP–TP were estimated to be 0.16, 0.18 and 0.29 V, respectively. In addition, differential pulse voltammograms (DPVs) of the nanocompsite electrode showed simultaneous determination of AA, DA, AP and TP with linear calibration plots from 5–650 μM, 1–700 μM, 5–700 μM and 1–600 μM where their detection limits were calculated to be 0.24 ± 0.03, 0.02 ± 0.01, 0.12 ± 0.04 and 0.03 ± 0.01 μM, respectively. Finally, the practical application of the (Au/Ag/Pd)NPs/EPGrO nanocomposite electrode was successfully conducted for the analytical determination of AA, DA, AP and TP in real sample of human blood serum. [ABSTRACT FROM AUTHOR]