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An effective nanocomposite sensor for selective electroanalytical dopamine (DA) determination using overoxidized conducting polymer of poly‐1,5‐diaminonaphthalene (OPoly‐1,5‐DAN) functionalized graphene nanosheets (GNS) was achieved. The OPoly‐1,5‐DAN/GNS nanocomposite polymer was prepared via an electropolymerization of 1,5‐DAN on GNS/GCE after 7 cycles of potential scan (−0.2 V to +0.9 V), followed by an electrooveroxidation of the nanocomposite Poly‐1,5‐DAN/GNS by the potential cycle (0.0 V to +1.8 V) for 2 scans. The OPoly‐1,5‐DAN was effectively designed by GNS as a uniformly distribution of nanocomposite that caused more accumulations of analyte due to large electrocatalytic active positions created on electrode surface. The high specific and sensitive performance of the OPoly‐1,5‐DAN/GNS nanocomposite polymer was conducted to greater effective electrons transferring behavior for DA with copresent of vitamin C (VC). The stable and suitable formation of OPoly‐1,5‐DAN/GNS nanocomposite polymer showed rapid charge transport voltammogram and obvious electrocatalytic activity to DA and eliminated VC response. Moreover, the OPoly‐1,5‐DAN/GNS displays an excellent responses to DA determination with wide linear range (LR) 1.0–150 μM and lower detection limit (DL) 8.82±0.1 nM as comparing with other studies. Additionally, the excellent reproducibility of OPoly‐1,5‐DAN/GNS as well as long‐term stability indicated that it is an excellent and effective electrochemical DA sensor. Finally, the electroanalytical application of the OPoly‐1,5‐DAN/GNS nanocomposite polymer was employed for the electroanalysis of DA in human urine. [ABSTRACT FROM AUTHOR]

Nonenzymatic sensors based on a metals nanocomposite with high sensitivity, selectivity, and stability has been received considerable interest. In this study, a novel electrochemical nanocomposite sensor based on palladium nanoclusters (PdNCs) decorated electrochemically activated graphene (EAGr) was established for highly sensitive nonenzymatic H2O2 sensor. The PdNCs/EAGr nanocomposite was fabricated via an electrochemical activation of Gr by the potential cycling in the range of +0.6 to −1.8 V, followed by the electrodeposition of PdNCs at −0.4 V applied potential. The homogeneous dispersion of PdNCs/EAGr nanocomposite were characterized by scanning electron microscopy (SEM), X‐ray photoelectron spectroscopy (XPS), cyclic voltammetry (CV), and linear sweep voltammetry (LSV). The PdNCs/EAGr nanocomposite electrode showed higher electrocatalytic activity towards the reduction of H2O2 in pH 7.0 of 0.1 M PBS by significantly enhancing the reduction peak current and reduced the reduction overpotential as well as eliminated other interfering species responses. The PdNCs/EAGr electrode displayed a wide linear range for H2O2 reduction from 1.0 to 1100 μM with limit of detection 0.02±0.01 μM. The higher sensitivity and selectivity as well as long‐time stability and excellent reproducibility obtained, indicating the proposed sensor is an effective H2O2 based sensor. In addition, the analytical application of the nancomposite sensor was successfully examined for the determination of H2O2 in the real sample of human urine indicating that the appreciable practicality of the nonenzymatic sensor for the determination of H2O2 in physiological fluids. [ABSTRACT FROM AUTHOR]

A new analytical strategy based on potentiostatically pretreated graphene/CNT nanocomposite encapsulated Au nanoparticles (AuNPs/PPG/CNT) for the fabrication of H2O2 sensor was developed. The PPG/CNT nanocomposite was obtained through the potentiostatical of G and CNT mixture solution at an applied potential of −1.8 V, while AuNPs were immobilized on the PPG/CNT film via the produced active sites in the nanocomposite structure. The morphology and structure of the AuNPs/PPG/CNT nanocomposite were investigated by transmission electronic microscopy (TEM), UV-visible spectroscopy, scanning electron microscopy (SEM) and electrochemical impedance spectroscopy (EIS). The nanocomposite displays intensive electrocatalytic activity towards the reduction of H2O2 by enhancing the cathodic peak current and completely eliminating the interference of other species. The AuNPs/PPG/CNT sensor showed an excellent amperometric response to H2O2 reduction with linear range from 1.0-150 µM and detection limit of 0.017 µM. Moreover, the sensor showed good reproducibility as well as anti-interfering ability and long term stability. In addition, the proposed sensor was further applied for analytical determination of H2O2 in human urine real samples. [ABSTRACT FROM AUTHOR]

An electrochemical sensor for the simultaneous determination of ascorbic acid (AA), dopamine (DA), uric acid (UA) and folic acid (FA) using gold nanoclusters (AuNCs)/activated graphene (AGR)/MWCNT nanocomposite was fabricated. The AGR/MWCNT nanocomposite was prepared via the electrochemical reduction of GR/MWCNT while AuNCs were formed onto the AGR/MWCNT film through the electrodeposition of Au. The AuNCs/AGR/MWCNT nanocomposite was characterized using different techniques, such as scanning electron microscopy (SEM), electrochemical impedance spectroscopy (EIS), X-ray photoelectron spectroscopy (XPS) and cyclic voltammetry (CV). The nanocomposite sensor exhibited sharp and obvious peaks for the oxidation of AA, DA, UA and FA as compared to a bare electrode. The AuNCs/AGR/MWCNT probe displays an efficient electron mediating behavior with well separated oxidation peak potentials between AA to DA, DA to UA and UA to FA were 0.21, 0.14 and 0.28 V, respectively. The linear calibration curves of AA, DA, UA and FA were observed from 10–150 μM, 1.0–210 μM, 5.0–100 μM and 10–170 μM with detection limits of 0.27 ± 0.1 μM, 0.08 ± 0.02 μM, 0.10 ± 0.03 μM and 0.09 ± 0.01 μM, respectively. In addition, the analytical application of the proposed sensor was successfully conducted for the determination of these species in human urine real samples. [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]