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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]

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]

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]

Highlights: [•] AgNPs modified Ox-pTTBA/MWCNT nanocomposite film for highly sensitive and selective H2O2 sensor. [•] Fast amperometric response with lowest detection limit was obtained for H2O2. [•] The reliability of the proposed sensor was evaluated using real samples analysis. [Copyright &y& Elsevier]

A simple detection method of ascorbic acid (AA) through selective catalytic oxidation has been developed using a novel conducting polymer poly-3′-(2-aminopyrimidyl)-2,2′:5′,2'-terthiophene (pAPTT). The pAPTT electrode showed an excellent selectivity in facilitating the electron transfer of AA and blocked the interferences of cationic species due to the positively charged pAPTT film. This method proved to be effective in the determination of AA in the presence of various biological interfering species. The dynamic range of AA detection was from 10 to 200 µM and the detection limit was 1.4±0.06 µM. [ABSTRACT FROM AUTHOR]

Abstract: A highly selective nitric oxide (NO) biosensor was developed by immobilizing microperoxidase (MP) onto the MWCNT-poly-5,2′:5′,2″-terthiophene-3′-carboxylic acid (PTTCA) nanocomposite. Catalase (CAS) and superoxide dismutase (SOD) co-immobilized on the probe successfully protected the interferences of H2O2 and O2 − during NO detection. The nanocomposite layer showed the direct electron transfer processes of the immobilized CAS, SOD, and MP simultaneously at −0.11/+0.04, −0.33/−0.27, and −0.47/−0.40V vs. Ag/AgCl. Au nanoparticles (AuNPs) were electrodeposited on a glassy carbon surface to enhance the sensitivity of the sensor probe. The layers of CAS/SOD/MP/MWCNT-PTTCA/AuNPs were characterized using SEM, XPS, and QCM. The CAS/SOD/MP/MWCNT-PTTCA/AuNPs probe showed an excellent performance in the electrocatalytic reduction of NO which was attributed to the heme group of MP. Experimental conditions affecting the sensitivity of the biosensor were optimized in terms of pH, temperature, and applied potential. The dynamic range of NO analysis was from 1.0 to 40μM with the detection limit of 4.3±0.2nM. The reliability of biosensor was examined for the determination of NO released from the real samples of rat liver, stomach (AGS), and intestinal (HT-29) cancer cells. [ABSTRACT FROM AUTHOR]

Abstract: 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 5.0–100μM, with a detection limit (k =3) of 0.1±0.01μM. 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. [Copyright &y& Elsevier]

Abstract: The electrochemical reduction of oxygen has been studied on two novel anthraquinone derivatives, 1,5-bis(2-anthraquinonyloxy)-3-oxapentane (AQ1), and 1,11-bis(2-anthraquinonyloxy)-3,6,9-oxaundecane (AQ2) having two quinone moieties with cyclic voltammetry (CV) and hydrodynamic voltammetry (HV). Anthraquinone derivative modified electrodes exhibited a well defined redox couple in an aqueous solution which is corresponding to (AQ/AQH2). The AQs adsorbed on the electrodes in the nanofiber network showed an electrocatalytic activity for the oxygen reduction with 620mV positive potential shift and the current enhancement in a phosphate buffer solution (pH 7.0) as compared to a bare electrode. The compounds having two quinone moieties (AQ1, AQ2) showed the doubly increased catalytic current compared with that bearing a single quinine moiety (9,10-AQ). HVs with a rotating ring-disk electrode showed that the reduction of oxygen at the modified electrodes mostly occurs through the two-electron pathway to form H2O2 as a final product. The rate constant (k) for oxygen reduction with AQ1 and AQ2 modified electrodes was determined to be 2.4×105 and 2.7×105 M−1 s−1, respectively. [Copyright &y& Elsevier]

• 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]

Abstract: Active electrocatalytic electrode designs are needed for the sensitive and selective detection of a single or multi-active biomolecule among biological components. We report the design of hierarchical NiO catalyst (HNC) for one-step monitoring of bioactive molecules such as ascorbic acid (AA), dopamine (DA), and uric acid (UA). The novel mesostructured geometries, active surface sites, and multi-diffused spaces for easy electron movement through gaps provide highly active electrocatalytic electrode designing surface. Controlled HNC architecture along electrode-design surface domains having double-head branches spread out along both sides of the dipole-like rod may lead to the vital electron transfer and fast response signaling of multi-bioactive molecules in one-shot triggering individually or simultaneously. Electrochemical analyses showed evidence that the proposed electrode design can detect each component up to 0.02 µM. Sensitive detection up to 1.127, 0.02, and 0.978 µM and wide-range responses of 25-800, 2-60, and 10-000 µM for AA, DA, and UA, respectively, were observed. The simultaneous monitoring and selective signaling of AA, DA, and UA in real urine samples in one step under different potentials were realized. Thus, the HNC-modified electrode can monitor and evaluate the coexistence of biomolecules simultaneously in multi-components.Graphical Abstract: The electrochemical oxidation of AA, DA, and UA at the HNC-modified electrode and the corresponding DPV peaks with losing of 2e−/2H+. [ABSTRACT FROM AUTHOR]

Fabrication of electrodes based on a metal-free catalyst with desirable sensitivity, selectivity, and stability has been given considerable interest. Microporous sulfur-doped carbon microspheres (S-MCMS) were synthesized and assembled as an electrochemical sensor for the monitoring of ascorbic acid (AA) in commercial juices and vitamin C tablets. The S-doped microporous carbon with a spherical structure was fabricated at different annealing temperatures (700, 800, and 900 °C) to achieve a high surface area, an actively doped carbon interfacial surface, soft interactive surfaces and an open microporous network. The high surface area, actively doped S-atom percentage, microporous construction, and active doping of the carbon microsphere construction of S-MCMS-900, make it a highly stable metal-free electrocatalyst for selective detection of AA. The S-atoms incorporated with the sp2-carbon matrix form numerous active sites, which bind to targets and stimulate the transduction of the electrochemical interaction with a fast response and high charge transfer efficiency. Selective monitoring of AA on S-MCMS-900 with high sensitivity was achieved with a detection limit as low as 1 μM, and wide linear range up to 4 mM. Monitoring of AA in lemon juice or pharmaceutical tablets was realized by using S-MCMS-900, with a fast response, high sensitivity, reliable selectivity, high stability and rational reproducibility. S-MCMS-900 can be employed as a fast, sensitive, and selective assay for routine detection of AA in food, biological, and environmental samples. [ABSTRACT FROM AUTHOR]

Herein, we have developed highly sensitive and selective non‐enzymatic bioinspired polydopamine derived nitrogen rich carbon (NC) coated bimetallic zeolitic imidazolate framework (BM‐ZIF) electrochemical sensor via simple hydrothermal approach for monitoring adrenaline (AD) from COVID‐19 quarantined person blood and pharmaceutical sample. The designed NC‐BM‐ZIF electrode shows excellent sensitive and selective performance towards AD monitoring with detection limit (LOD) of 0.01 nM and 0.1931 μA/nM/cm2 sensitivity over a wide linear range of 50–1625 nM. To the best of our knowledge, this is the first study of using of NC‐BM‐ZIF electrode for the electrochemical sensing of AD from quarantined person blood and pharmaceutical sample. [ABSTRACT FROM AUTHOR]

Multifunctional nanoparticles, which incorporate diagnostic (quantum dots, magnetic, metallic, polymeric and silica nanoparticles) and/or therapeutic (magnetic and metallic nanoparticles) properties, are in the process of development. They have been used in vivo to protect the drug entity in the systemic circulation, restrict access of the drug to the chosen sites and to deliver the drug at a controlled and sustained rate to the site of action. The surface of gold nanoparticles can be tailored by ligand functionalization to selectively bind biomarkers. Thiol-linking of DNA and chemical functionalization of gold nanoparticles for specific protein/antibody binding are the most common approaches. Several methods have been utilized for detecting AuNPs such as scanometric, fluorescence, colorimetric, surface-enhanced Raman scattering and electrochemical techniques. These unique aspects have allowed the development of novel AuNP-based assays for clinical diagnostics which promise increased sensitivity and specificity, multiplexing capability, and short turnaround times. This article focuses on nanoparticle, application in clinical diagnosis and therapeutics especially with reference with gold nanoparticle. [ABSTRACT FROM AUTHOR]

Bioinspired nitrogen-rich carbon-coated zeolitic imidazolate framework-8 (NRC@ZIF-8) has been prepared by simple impregnation and carbonization of novel N rich C source "nitrodopamine" (NDA) with ZIF-8 through eco-friendly solvothermal approach and employed as an electrocatalyst for oxygen reduction reaction (ORR). Fabricated NRC@ZIF-8 nanocomposite-based electrode offers surprisingly high ORR electrocatalytic activity by providing high anchoring sites for O 2 adsorption due to the availability of positively charged N atoms of nitro group, increased surface defects, improved surface compatibility, promote heterolytic O–O bond cleavage rather than homolytic cleavage and offer fast electron transportation capability. Additionally, it improves interfacial binding efficacy due to functionalization of nitro group with ZIF-8, thus leading to high half wave potential value (E 1/2 = 0.91 V), high tolerance against methanol poisoning (91.88%) and remarkable stability even better than dopamine (DA) derived nitrogen carbon-coated ZIF-8 (NC@ZIF-8), commercial Pt/C and other related bioinspired materials. • Fabrication of novel bioinspired N rich C coated zeolitic imidazolate framework-8 (NRC@BM-ZIF). • The novel NRC@BM-ZIF provides positively charged O 2 adsorption sites to support ORR. • Our system promotes heterolytic O–O bond cleavage rather than homolytic cleavage. • Our system offers high half wave potential value and high tolerance against methanol poisoning. [ABSTRACT FROM AUTHOR]

[Display omitted] • The CuO nanosheets (CuO NSs)/cellulose acetate butyrate (CAB) were synthesized. • The CuO NSs/CAB-based electrode is a highly active surface for electrooxidation of hydrazine. • Sensitive and selective hydrazine assay is designed with a low detection limit and wide linear range. • Real monitoring of hydrazine in tap water is successfully achieved. Synthesis of electrode materials with stable and advanced functionality is highly required to design susceptible and selective electrochemical sensors to fast screen various targets such as hazardous environmental analytes. A nanocomposite-based electrode material was synthesized for hydrazine (HZ) detection in environmental samples. The CuO nanosheets (CuO NSs) decorated the surface of Cellulose acetate butyrate (CAB) were synthesized by a simple and one-step approach. The materials of CuO NSs/CAB and CAB were characterized using field emission scanning electron microscopy (FE-SEM), Fourier transform-infrared spectroscopy (FT-IR), X-ray diffraction (XRD), Raman spectroscopy, and ultraviolet (UV). The designed material of CuO shows a nanosheet structure with irregular sheet size and distribution and a sheet size of ∼17 nm. The CAB rough surface, high surface, and functionalization (i.e., OH, acetate and butyrate) increase the loading of CuO nanosheet that enhance the catalytic active sites. Moreover, the structural morphology and composition of CuO NSs/CAB play a key role in the design of a highly active surface for electrocatalytic oxidation of HZ molecules. The CAB was decorated by CuO NSs and acted as the mediated surface for catalytic oxidation and signalling transduction of HZ molecules. The CuO acted as the active electrocatalyst, and the CAB acted as a hydrophilic surface to induce the binding and loading of HZ molecules. The CuO NSs/CAB shows a highly sensitive sensor with a low limit of detection (0.15 µM) and a wide linear range of 0.5–100 mM. The designed electrode of CuO NSs/CAB provides a selective sensor assay for the detection of HZ in environmental samples with a high recovery range of 96.34–99.64 %, high stability, and good reproducibility. [ABSTRACT FROM AUTHOR]