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A selective detection method for dopamine (DA) was developed by incorporating cibacron blue (F3GA) into poly-1,5-diaminonaphthalene (PDAN) layer. Scanning electron microscopy (SEM), X-ray photoelectron spectroscopy (XPS), and cyclic voltammetry (CV) were employed to characterize the modified surfaces. The modified electrode was effective in selectively facilitating the electron transfer of DA and blocking the interferences of negatively charged species attributed to the sulfonate groups in the F3GA/PDAN composite film. This method enabled the determination of DA in the presence of various interfering species, including ascorbic acid (AA), in a phosphate buffer solution (pH 7.4). The modified electrode demonstrated good performance in the detection of DA in a concentration range of 5.0-100 microM, with a detection limit (k=3) of 0.1+/-0.01 microM. The application was conducted for the determination of DA in a human urine sample and the sensor was proven to be rapid, has excellent selectivity, and stable amperometric response.

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]

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]

Fabrication of nonenzymatic biosensors based on the nanomaterials for highly sensitive and selective detection of single or multiple molecules coexisting in one biological sample is extremely challenging. Design of the hierarchical nanohexagonal Fe2O3 platelets (HFP) via one-pot hydrothermal treatment was employed for selective signaling of dopamine (DA) and uric acid (UA) in the presence of ascorbic acid (AA) with high sensitivity. Electrode design with the nanosized structure of parallel hexagonal platelets (20-40 nm), high surface area, multiactive site, smooth surface, and pore distribution inside/outside the surfaces renders excellent sensitivity and selectivity of DA and UA during the catalytic oxidation process. Simultaneous monitoring and selective signaling of DA and UA were successfully achieved by HFP with detection limits as low as 16 nM and 0.218 μM with a wide linear range from 1 to 200 μM and from 20 to 400 μM for DA and UA, respectively. HFP provides high stability and reproducibility with relative standard deviations in the range of 2.5-5.29% to monitor DA and UA. Furthermore, continuous monitoring of DA and UA in real human saliva/serum samples was realized with high sensitivity and selectivity. The designed HFP can be employed as a nonenzymatic biosensor for simultaneous detection of mono-bioactive molecules in the biological samples.The electrooxidation of DA and UA at the surfaces of Fe2O3.The electrocatalytic active sites bind with the DA and UA through hydrogen bonds at the surface of Fe2O3. Through the DPV or CV scanning, the electrooxidation of DA and UA proceeded and the oxidized form quinolone-DA and keto-UA were obtained with losing of 2e−/2H+. [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]