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In this study, simultaneous determination of toxic hydrazine and nitrite was performed on composite electrodes of poly(Nile blue)(NB), carbon nanotube(CNT) and gold nanoparticles(AuNPs). The prepared AuNPs/CNT/poly(NB)/GCE was used for as a sensor platform for individual and simultaneous determination of hydrazine and nitrite. Electrodes were characterized by HRTEM, SEM, XPS, EIS. The LOD for nitrite and hydrazine was 5.0 mu M and 3.1 mu M at AuNP/CNT/poly(NB)/GCE, respectively. Also, sensitive amperometric determinations of hydrazine and nitrite were performed and LOD were calculated as 0.33 mu M and 0.68 mu M, respectively. The method was applied to sausage and river water samples and recovery results were obtained in the range 85-115 %.

A glassy carbon electrode, modified with gold nanoparticles/over-oxidized poly-eriochrome black T film, was fabricated for sensitive determination of As(III) by stripping voltammetry in an acidic medium. The electrode surface properties were characterized by cyclic voltammetry, electrochemical impedance spectroscopy, scanning electron microscope (SEM), and X-ray photoelectron spectroscopy (XPS). The electrode demonstrated a good response towards As(III), with a detection of 0.077 ?M and good linearity in the range of $0.1 to 10 ?M (R^2 = 0.9977)$. For the determination of As(III), the fabricated electrode was placed in different mineral water samples, acidified with 0.75 M HCl solution, spiked with various concentrations of As(III). Spiked recoveries for mineral water samples were obtained in the range of 100.3%–105.0%. The relative standard deviations were lower than 4.0%.

An electrochemical sensor was fabricated by construction of nickel nanowires on the surface of poly(p-aminophenol) (PPAP) modified glassy carbon electrode. The electrochemical response of dicofol, a known pesticide and used for agricultural activities such as cyclic voltammetry and differential pulse voltammetry, were investigated and the results were compared with those obtained unmodified electrodes. Following the optimization of NaOH concentration, polymerization cycle number, Ni nanowire amount, the linear range for the dicofol was studied and found as 0.83-30.7 mu mol L-1 (R-2=0.9981) at Ni/PPAP/GCE with a 0.08 mu mol L-1 detection limit according to S/N=3. Finally, the proposed Ni/PPAP/GCE sensor was successfully applied for the dicofol analysis in soil samples. The characterization of the developed surface was carried out by scanning electron microscopy and X-Ray photoelectron spectroscopy.

This study reports a detailed analysis of an electrode material containing poly(phenolphthalein), carbon nanotubes and gold nanoparticles which shows superior catalytic effect towards to hydrazine oxidation in Britton-Robinson buffer (pH 10.0). Glassy carbon electrode was modified by electropolymerization of phenolphthalein (PP) monomer (poly(PP)/GCE) and the multiwalled carbon nanotubes (MWCNTs) was dropped on the surface. This modified surface was electrodeposited with gold nanoparticles (AuNPs/CNT/poly(PP)/GCE). The fabricated electrode was analysed the determination of hydrazine using cyclic voltammetry, linear sweep voltammetry and amperometry. The peak potential of hydrazine oxidation on bare GCE, poly(PP)/GCE, CNT/GCE, CNT/ poly(PP)/GCE, and AuNPs/CNT/poly(PP)/GCE were observed at 596 mV, 342 mV, 320 mV, 313 mV, and 27 mV, respectively. A shift in the overpotential to more negative direction and an enhancement in the peak current indicated that the AuNPs/CNT/poly(PP)/GC electrode presented an efficient electrocatalytic activity toward oxidation of hydrazine. Modified electrodes were characterized with High-resolution transmission electron microscopy (HRTEM), scanning electron microscopy (SEM), X-ray photoelectron spectroscopy (XPS) and electrochemical impedance spectroscopy (EIS). Amperometric current responses in the low hydrazine concentration range of 0.25-13 µM at the AuNPs/CNT/poly(PP)/GCE. The limit of detection (LOD) value was obtained to be 0.083 µM. A modified electrode was applied to naturel samples for hydrazine determination. © This work is licensed under a Creative Commons Attribution 4.0 International License., 2018-097, This work was supported by Manisa Celal Bayar University Research Foundation Project No: 2018-097. Part of the SEM experiments in this article were performed at Manisa Celal Bayar University (Turkey)-Applied Science and Research Center (DEFAM).

Nickel nanoparticles incorporated with graphene oxide composite-glassy carbon electrode (Ni-GO/GCE) was constructed via a facile electrochemical method for sensitive and selective determination of rutin. The surface morphology, surface chemistry and conductance of the prepared electrodes were characterized by scanning electron microscopy (SEM), high resolution transmission electron microscopy (HRTEM), X-Ray photoelectron spectroscopy (XPS) and electrochemical impedance spectroscopy (EIS). The electrochemical behaviour of rutin on the Ni-GO/GCE was investigated by using of cyclic voltammetry technique. The composite electrode was also used for the detection of rutin with square wave voltammetry. The results indicated that under optimized conditions, the anodic peak current (Ipa) of rutin was found to be proportional to its concentration over two linear ranges 1.1 × 10−8–1.0 × 10−6 mol L−1 and 2.2 × 10−6–1.5 × 10−5 mol L−1, and a low detection limit of 3.2 × 10−9 mol L−1 was observed with the developed electrode. Interference studies were also performed in the presence of inorganic and organic compounds. Moreover, the Ni-GO/GCE was successfully applied for the determination of rutin in pharmaceutical formulations and remarkable sensitivity with acceptable recoveries were obtained.

In this work, we prepared modified copper phthalocyanine-carbon nanotube (CuPc-CNT) catalysts containing bimetallic (Au-Pt, Au/Pt, Pt/Au) and monometallic nanoparticles (Au or Pt), using a simple electrochemical technique. We investigated the catalyst structural and physical properties by scanning electron microscopy, transmission electron microscopy, X-ray diffraction, thermogravimetric analysis, and electrochemical impedance spectroscopy. The bimetallic systems (Au-Pt/CuPc-CNT > Pt/Au/CuPc-CNT > Au/Pt/CuPc-CNT) proved to have a better current density towards methanol oxidation than that of mono-metallic systems (Pt/CuPc-CNT > Au/CuPc-CNT) in alkaline media. The electrochemical surface area (ECSA) of Au-Pt/CuPc-CNT was found to be 60.25 m(2) g(-1). The methanol oxidation reaction took place with the electron transfer, followed by the catalytic chemical reaction. Thus, the electrochemically-prepared Au-Pt/CuPc-CNT catalyst of the highest stability and enhanced electrocatalytic activity towards methanol oxidation represents a promising candidate for use in alkaline direct methanol fuel cells., Ege University Research Funds [12 FEN/039], This work was supported by Ege University Research Funds (project no: 12 FEN/039) . The author would like to thank TuBITAK-BIDEB for providing financial support during this study, which is produced from a PhD thesis study.

2-s2.0-85041864597, A copper nano particles and cerium (IV) oxide modified carbon nanotube based composite on glassy carbon electrode (Cu?CeO2/MWCNT/GCE) was fabricated for simultaneous determination of guanine and adenine. The surface morphology, chemistry and conductance of the prepared electrodes were characterized by scanning electron microscopy (SEM), energy dispersion X-ray (EDX), X-Ray photoelectron spectroscopy (XPS) and electrochemical impedance spectroscopy (EIS). The Cu?CeO2/MWCNT/GCE improved electrochemical behaviour of guanine and adenine compared to other electrodes. The modified electrode was also used for individual and simultaneous determination of guanine and adenine. Under optimized conditions, the calibration curves were obtained linearly in the range of 0.20 to 6.00 ?M for the guanine and 0.10 to 8.0 ?M for the adenine by differential pulse voltammetry. The limits of detection of guanine and adenine were calculated as 0.128 and 0.062 ?M, respectively. Interferences studies were also performed in the presence of inorganic and organic compounds. Moreover, the determination of guanine and adenine contents were carried out in a calf thymus DNA sample by the developed method with satisfactory results. © 2018 Wiley-VCH Verlag GmbH & Co. KGaA, Weinheim, British Association for Psychopharmacology: 14 FEN/059, This work was supported by Ege University Research Funds (BAP Project No: 14 FEN/059).

Zinc oxide nanoparticles doped graphene oxide modified glassy carbon electrodes (Zn-GO/GCE) were fabricated for easy, cheap and practical detection of atenolol (ATE). the morphological and chemical characterizations of modified electrodes were carried out with scanning electron microscopy (SEM), electron diffraction spectroscopy (EDS) and X-Ray photoelectron spectroscopy (XPS). the amounts of the electrode modifiers and the differential pulse voltammetric parameters were optimized due to exhibited the best analytical response towards the determination of ATE. As a result, the calibration curves of ATE were obtained at Zn-GO/GCE using DPV technique with two different linear parts: 7.8 - 84 mu mol L(-1)and 167 mu mol L-1- 639 mu mol L-1. the detection limit (LOD) was also calculated as 2.50 mu mol L-1. the fabricated electrode in this study is selective for ATE in the presence of some electroactive molecules. the practical, easy and cheap modified electrode was applied for the detection of ATE in atenolol medicine tablets with good recovery., BAP ProjectTurkiye Cumhuriyeti Kalkinma Bakanligi [17 FEN 079], The authors gratefully acknowledge the support of this work by Funds (BAP Project No: 17 FEN 079).

Dimethylamine borane (DMAB) is a promising fuel alternative for fuel cell applications. In this work cyclic voltammetric behavior of DMAB was investigated on the polymerized aminophenol film decorated with Ag nanoparticles in alkaline media. The polymer film was formed on the glassy carbon electrode by electrochemical technique and then, the surface was modified with Ag nanoparticles. The surface of the modified electrode was identified by scanning electron microscopy, transmission electron microscopy, X-ray photoelectron spectroscopy, and electrochemical impedance spectroscopy techniques. The developed electrode has displayed high electrocatalytic activity for DMAB oxidation in alkaline media depending on the supporting electrolyte concentration. Experimental parameters such as cycle number used in electropolymerization of p-aminophenol, deposition of Ag nanoparticles and supporting electrolyte were optimized.

Electrochemical behaviour of oxygen was investigated at nickel-copper bimetallic particles covered into poly (ethylenedioxythiophene) modified glassy carbon electrode (Ni-Cu/PEDOT/GCE). the characterization tools which are energy-dispersive X-ray spectroscopy (EDX), scanning electron microscopy (SEM), transmission electron microscopy (TEM), and electrochemical impedance spectroscopy (EIS) were used to identify the mor-phology and chemical structure of the modified electrode surfaces. the best catalytic effect regarding to peak potential and peak current for O-2 reduction were obtained with the Ni-Cu/PEDOT/GCE. the hydrodynamic studies have shown that the reduction of oxygen occurs via almost four electron transfer on the Ni-Cu/PEDOT/GCE., Ege University Research Funds (BAP project)Ege University [2012 FEN/077], This work was supported by Ege University Research Funds (BAP project, 2012 FEN/077).

Dimethylamine borane (DMAB) is a promising fuel alternative for fuel cell applications. In this work cyclic voltammetric behavior of DMAB was investigated on the polymerized aminophenol film decorated with Ag nanoparticles in alkaline media. The polymer film was formed on the glassy carbon electrode by electrochemical technique and then, the surface was modified with Ag nanoparticles. The surface of the modified electrode was identified by scanning electron microscopy, transmission electron microscopy, X-ray photoelectron spectroscopy, and electrochemical impedance spectroscopy techniques. The developed electrode has displayed high electrocatalytic activity for DMAB oxidation in alkaline media depending on the supporting electrolyte concentration. Experimental parameters such as cycle number used in electropolymerization of p-aminophenol, deposition of Ag nanoparticles and supporting electrolyte were optimized. © TÜBİTAK.

WOS: 000501620800017, Herein, a new facile and sensitive method was developed that enables the individual and simultaneous determination of catechol (CC) and hydroquinone (HQ) using an over-oxidized and electrochemically polymerised rutin film glassy carbon electrode. the proposed electrode exhibits a large peak potential difference between CC and HQ resulting in well-separated peaks-an important factor for selective determination. CC and HQ were individually and simultaneously determined via differential pulse voltammetry in a pH -7.2 phosphate buffer solution. the individually calculated detection limits for CC and HQ were 8.8 and 52 nM, respectively. in simultaneous determination, the limits of detection were calculated to be 31 and 53 nM for CC and HQ respectively. Moreover, real sample analyses were successfully conducted using tap and waste water. (C) 2019 Elsevier B.V. All rights reserved.

Metal-organic frameworks (MOFs) are porous coordination polymers (CP) produced by metal-based nodes and multitopic organic ligands. Based on their porous and microcrystalline powder structures, they have initially been used for storage, catalysis and separation. Then, because of their advantageous properties like ease of the tailoring, they also have been applied in areas like chemical sensing, biological applications, etc. The CPs were combined with molecules such as organic dyes, small biomolecules, nanomaterials like nanoparticles, nanowires, nanofibers and polymers and as a result, composite MOFs have been produced. By this way, better mechanical stability, conductivity, and catalytic performance were obtained. This review (with 135 refs.) summarizes the progress made in the past years in the field of electrochemical and optical sensing based on the use of MOFs. Following an introduction into the field, large sections cover MOF based sensors exploiting (a) carbon nanomaterials (with subsections on carbon nanotubes, graphene and its derivatives), (b) metal/metal oxide MOFs; including gold, silver, copper and/or copper oxide nanoparticle and other metal/MOF composites. Enzyme mimicking MOFs are discussed next. In this context, after the brief information about focused MOFs, the nanomaterial/MOF composites were discussed and related examples were presented. Graphical abstract MOF structures in Sensing Systems.

In this study, we introduce a very sensitive and selective method for the differential pulse anodic stripping determination of Sb(III) ion on the over-oxidized poly(phenol red) modified glassy carbon electrode (PPhRedox/GCE) in 0.1 mol L-1 HCl medium. The formation of both poly(phenol red) and over-oxidized poly(phenol red) film on the electrode surfaces were characterized by electrochemical impedance spectroscopy, X-ray photoelectron spectroscopy and scanning electron microscopy techniques. An anodic stripping peak of Sb(III) was observed at 0.015 V on the PPhRedox/GCE. Higher anodic stripping peak current of Sb(III) was obtained at PPhRedox/GCE compared with both bare GCE and poly(phenol red) film modified GCE (PPhRed/GCE). The calibration graph consisted of two linear segments of 0.044 - 1.218 μg L−1 and 3.40 – 18.26 μg L−1 with a detection limit of 0.0075 μg L−1. The proposed over-oxidized polymer film modified electrode was applied successfully for the analysis of antimony in different spiked water samples. Spiked recoveries for water samples were obtained in the range of 93.0–103.0%. The accuracy of the method was also verified through the analysis of standard reference materials (SCP SCIENCE-EnviroMAT™ EP−L-2).

A highly active electrocatalyst has been developed based on poly(p-aminophenol) polymer film modified with Pt-Au bimetallic particles on a glassy carbon electrode (Pt-Au/PPAP/GCE) for electrocatalytic reduction of oxygen. The surface morphology and chemical analyses of the modified electrodes have been revealed by scanning electron microscopy (SEM), transmission electron microscopy (TEM), energy-dispersive X-ray spectroscopy (EDX), and electrochemical impedance spectroscopy (EIS). The Pt-Au/PPAP/GCE has shown the best electrocatalytic activity towards O2 reduction in comparison to the other used electrodes. The rotating disk electrode (RDE) studies have indicated that the oxygen reduction reaction takes place via almost four electrons on the Pt-Au/PPAP/GCE.

EgeUn###, The attractive features of nanomaterials enable them to be used in a variety of areas including drug delivery (DD) systems. The advantages like better targeting and effective delivery, promote the usage of these materials in the structure of DD. However, the hazardous effects of nanomaterials must be considered before allowing them to be utilized in vivo. Because of their metallic based natures and small dimensions, nanomaterials can be toxic to human beings. Therefore the cons and pros of the usage of nanomaterials in DD systems must be extensively considered. In this review, after the brief history of DD systems and the usage of nanomaterials in these systems were presented, the selected nanomaterials cons and pros towards DD were examined. In conclusions and feature perspective part, the inadequacy of numbers of in-vivo studies was discussed and the need for more in-vivo tests was emphasized.

This work reports the synthesis of new symmetrically substituted manganese(III) phthalocyanine (2eOHMnPc) (2) containing tetra 5-chloroquinolin-8-yloxy group at the peripheral position for the first time. Manganese(III) phthalocyanine (2) was synthesized by cyclotetramerization of 4-(5-chloroquinolin-8-yloxy)phthalonitrile (1) in the presence of corresponding metal salt (manganese(II) chloride). This peripherally substituted phthalocyanine complex (2) was purified by column chromatography and characterized by several techniques such as IR, mass and UV-Visible spectral data. This novel synthesized phthalocyanine was mixed with multiwalled carbon nanotubes in order to prepare the novel catalytic surface on glassy carbon electrode for theophylline and caffeine detection in acidic medium. The novel composite electrode surfaces were characterized by scanning electron microscopy and electrochemical impedance spectroscopy. Individual and simultaneous determination of theophylline and caffeine were studied by differential pulse voltammetry. The detection limits were individually calculated for theophylline and caffeine as 6.6 x 10(-9) M and 5.0 x 10(-8) M, respectively. In simultaneous determination, LODs were calculated for theophylline and caffeine as 8.1 x 10(-9) M and 3.0 x 10(-7) M, respectively. The practical applicability of the proposed modified electrode was tested for the determination of theophylline and caffeine in green tea, cola and theophylline serum.

WOS: 000503910000014, In this work, composite electrode was prepared with poly L-methionine and carbon nanotube (PLM/MWCNT) onto glassy carbon electrode. the composite electrode surface morphology and electrical properties were characterized by scanning electron microscopy (SEM) and electrochemical impedance spectroscopy (EIS). Electrochemical response of Gallic acid (GA) on PLM/MWCNT/GCE was studied by cyclic voltammetry (CV), differential pulse voltammetry (DPV) and amperometry. the results demonstrated that PLM/MWCNT/GCE exhibit a favorable application for the determination of GA in pH 2.2 Britton-Robinson buffer solution. the prepared composite electrode offered two linear segments for GA in DPV over the range of 4.0 nmoL L-1 -1.1 mu mol L-1 and 1.7 mu mol L-1 - 20.0 mu mol L-1 with a detection limit of 3.1 nmol L-1 (S/N = 3). the amperometric detection was also used for improving as lower detection limit compare with DPV. the detection limit was calculated from the amperometric studies found as 0.5 nmol L-1. Through the synergistic effect of PLM and MWCNT, the composite electrode exhibits good catalytic effect, selectivity, stability and reproducibility for GA. the proposed method was verified by successful determination of GA in green tea, black tea and wine samples.

A silver nanoparticle decorated poly(thiophene) modified glassy carbon electrode (GCE) was prepared for determination of caffeic acid. The Ag/PTh/GCE surface was characterized by scanning electron microscopy (SEM) and energy-dispersive X-ray (EDX) spectroscopy. The modified electrode has shown higher electrocatalytic activity towards the oxidation of caffeic acid. The peak current of was found linear in the concentration range from 1.00×10−8 to 4.83×10−6 M with a detection limit of 5.3×10−9 M (S/N=3). The modified electrode was used for determination of CA concentration in red wine samples. The thermodynamic constants, entropy change (ΔS), enthalpy change (ΔH) and Gibbs free energy change (ΔG) were calculated as −166.34 J/(mol K), −154.24 kJ/mol and −104.75 kJ/mol at 25 °C, respectively.

The effect of solution composition and the type of the anionic species on the electrochemical formation of mixed-valent molybdenum oxide on a glassy carbon and ITO electrode surfaces was elucidated. Susccessive recording of the voltammograms has shown that anionic species display different stabilizing effect on the reductive formation of hydrogen molybdenum bronzes [MoO3−x (OH)x] and chloroacetic acid buffer has given the best results. The deposit was built upon cycling the potential between 0 and −0.9 V (vs. Ag/AgCl) via reduction of Mo(VI) to Mo(V) on the electrode surface in pH 3.0 chloroacetic acid solution. Electrochemical impedance measurements carried out in this medium revealed a shift in potential zero charge values from -0.2 V to -0.55 V after the potential of the GCE had been cycled for 30 min. An establishment of mixed-valent molybdenum oxide deposit by time on the gold electrode surface was proved by quartz crystal microbalance measurements. Atomic force and scanning electron microscopy techniques were made use of so as to characterize the surface structures of the electrodes. X-ray photoelectron spectroscopy studies confirmed that the deposit contains both Mo(V) and Mo(VI). The deposited films exhibited unique catalytic activity towards nitrite oxidation consistent with the change in peak characteristics.

A new approach is described for the photoelectrocatalytic oxidation of Reduced s-Nicotinamide Adenine Dinucleotide (NADH). It is based on a glassy carbon electrode (GCE) modified with a film of poly-Neutral Red (poly-NR) that is obtained by electropolymerization. Electrochemical measurements revealed that the modified electrode displays electrocatalytic and photo-electrocatalytic activity towards oxidation of NADH. If irradiated with a 250-W halogen lamp, the electrode yields a strongly increased electrocatalytic current compared to the current without irradiation. Amperometric and photo-amperometric detection of NADH was performed at +150 mV vs. Ag/AgCl/KClsat and the currents obtained are linearly related to the concentration of NADH. Linear calibration plots are obtained in the concentration range from 1.0 μM to 1.0 mM for both methods. However, the slope of the current-NADH concentration curve of the photo-electrocatalytic procedure was 2-times better than that obtained without irradiation.

It was firstly described that a glassy carbon electrode electropolymerized with methylene blue shows an efficient photoelectrocatalytic activity towards NADH oxidation in a phosphate buffer solution (pH 7.0). In order to perform the photoelectrocatalytic determination of NADH in a flow injection analysis (FIA) system, a home-made flow electrochemical cell with a suitable transparent window for the irradiation of the electrode surface was constructed. The currents obtained from the photoamperometric measurements in the FIA system at optimum conditions (flow rate of carrier solution, 1.3 mL min−1; transmission tubing length, 10 cm; injection volume, 100 μL; and constant applied potential, +150 mV vs. Ag/AgCl) were linearly dependent on the NADH concentration and linear calibration curves were obtained in the range of 1.0 × 10−7–2.0 × 10−4 M. The detection limit was found to be 4.0 × 10−8 M for photoamperometric determination of NADH.

A modified electrode was fabricated by electrochemically deposition of Pt nanoparticles on the multiwall carbon nanotube covered glassy carbon electrode (Pt nanoparticles decorated MWCNT/GCE). A higher catalytic activity was obtained to electrocatalytic oxidation of ascorbic acid, dopamine, and uric acid due to the enhanced peak current and well-defined peak separations compared with both, bare and MWCNT/GCE. The electrode surfaces were characterized by scanning electron microscopy (SEM), X-ray diffraction (XRD) and electrochemical impedance spectroscopy (EIS). Individual and simultaneous determination of AA, DA, and UA were studied by differential pulse voltammetry. The detection limits were individually calculated for ascorbic acid, dopamine, and uric acid as being 1.9×10−5 M, 2.78×10−8 M, and 3.2×10−8 M, respectively. In simultaneous determination, LODs were calculated for AA, DA, and UA, as of 2×10−5 M, 4.83×10−8 M, and 3.5×10−7 M, respectively.

Oxygen reduction was studied on palladium, cadmium and zinc ad-atom modified single crystal Au(111) electrodes. The electrodes were modified by underpotential deposition process and their activity towards oxygen reduction was studied in alkaline media by voltammetry. The reduction peaks obtained were compared with those of bare Au(111), Pd disc and bulk deposited Cd electrodes. Enhanced catalytic activity of the Au(111) electrode in the presence of Pd, Cd and Zn ad-layer can be attributed to a change in surface charge and energy by ad-layer formation. In oxygen saturated medium a well defined sharp reduction peak was observed at −0.12 V for 1/5 ML Pd ad atom modified Au(111) electrode while it was positioned at −0.18 V on a Pd disk electrode. The best shift in reduction peak potential was obtained with 2/5 ML Pd ad atom modified Au(111) electrode with similar current density of Pd disc electrode.

A new biosensor for the voltammetric detection of hydrogen peroxide was developed based on immobilization of catalase on a clinoptilolite modified carbon paste electrode using bovine serum albumin and glutaraldehyde. The biosensor response was evaluated according to electrode composition, reaction time, solution pH and temperature. The voltammetric signals were linearly in proportion to H2O2 concentration in the range 5.0 x 10(-6) - 1.0 x 10(-3) M with a correlation coefficient of 0.9975. The detection limit is 8.0 x 10(-7) M and the relative standard deviation for 4.0 x 10(-4) M hydrogen peroxide was 1.83% (n = 6). The biosensor exhibited high sensitivity, and it was determined that it could be used for more than 2 months. In addition, the biosensor was successfully applied for the determination of hydrogen peroxide in milk samples.

The adsorption of methylene blue (MB) onto zirconium phosphate (ZrP) was studied and the adsorption capacity value and isotherms were determined. The adsorption capacity of ZrP was increased after being exposed to gas phase n-butyl amine. The adsorbed MB on ZrP was used as a modifier material in carbon paste electrode (MCPE), which in turn was used in voltammetric investigations and flow injection (FI) amperometric determination of ascorbic acid (AA). A quasi-reversible electrode reaction of adsorbed MB was exhibited. A home made flow-through electrochemical cell with a suitable transparent window for irradiation of the electrode surface was constructed and used for amperometric FI studies. The photoamperometric-FI conditions were optimised as 1.5 mL min(-1) flow rate, a 25 cm transmission tubing length, a 100 mu L injection volume, and a constant applied potential of +100 mV versus SCE. The calibration curve for AA was linear over the concentration range from 1.0 x 10(-6) to 4.0 x 10(-5) M. The relative standard deviation of four replicate injections of 3.0 x 10(-5) M AA was 1.2 %. The results obtained for AA determination in pharmaceutical products are in good agreement with those obtained using the procedure involving the reaction between triiodide and AA. (c) 2005 Elsevier B.V. All rights reserved. (Less)

Oxygen reduction reaction was investigated in an O2-saturated 0.1 M NaOH solution at Au(111) single crystal electrodes modified with various ad-metals (Cu, Ag and Bi) by underpotential deposition (upd). An increase in the catalytic activity was observed upon deposition of metal ad-atoms submonolayer for all prepared electrodes: Cu ad-layer was found, for the first time, to show a very interesting positive catalytic effect in contrast with reported data in acidic media, i.e., an apparent four-electron reduction process due to considerable enhancement of the disproportionation of hydrogen peroxide on the 1/3 monolayer (ML) Cu-modified Au(111) electrode. An interesting catalytic activity was also obtained at the 1/3 ML Ag ad-atoms modified Au(111) electrode, where a significant increase in reduction current was shown to suggest a four-electron reduction of oxygen to water. The Bi ad-atoms modified Au(111) electrode, Bi(2×2)–Au(111), showed positive catalytic activity by a limiting current of twice higher than at a bare Au(111) electrode with peak potential at ca. −0.38 V vs. Ag|AgCl|KCl(sat). Keywords: Fuel cells, Oxygen reduction, Electrocatalytic activity, Au(111) electrode, upd

The electrochemical behavior of a copper(I)oxide (Cu2O) modified carbon paste electrode (MCPE) was investigated in different buffer solutions and in the presence of ascorbic acid (AA) and cysteine (RS). Working conditions such as pH, mineral oil, and modifier ratio were optimized. Voltammetric results revealed that RS forms rather stable complexes with Cu(I) which has a high electrocatalytic reduction peak current at −0.65 V versus SCE in borate buffer (pH 9.2). In the case of AA, a complexation occurred with Cu(II) species at the electrode surface, rather than Cu(I). The electrocatalytic reduction peak current of the Cu(II)–AA complex was observed at −0.07 V in phosphate buffer at pH 6.9. Linear responses were observed in the range 2.0×10−9 to 3.0×10−8 M with a 0.9954 correlation coefficient for RS and 1.0×10−9 to 2.0×10−8 M with a 0.9961 correlation coefficient for AA.

Glucose oxidation in a 0.1 M NaOH solution at Au(1 1 1) single crystal electrodes modified with various ad-metals (Cu, Ag, Ru, Pt, Pd and Cd) by underpotential deposition (upd) was investigated. Ag ad-atoms of 1/3 monolayer (ML) onto the Au(1 1 1) surface showed the highest catalytic activity for glucose oxidation: The peak potential for glucose oxidation to gluconolactone (two-electron oxidation) was around −0.40 V vs. Ag|AgCl|KCl(sat), and the catalytic effect of this electrode on the oxidation of gluconolactone was also observed around −0.1 V vs. Ag|AgCl|KCl(sat) to give formate as the main product in a 0.1 M NaOH solution. Full coverage of Ag ad-atoms, however, led to a decrease in peak current with no marked shift in potential for glucose oxidation, but suppressed the oxidation of gluconolactone significantly. Cu ad-atoms modified Au(1 1 1) electrodes showed a slight negative shift of the pre-peak in the oxidation of glucose with a small oxidation current and a main oxidation peak appeared around −0.04 V vs. Ag|AgCl|KCl(sat). Cd ad-atoms gave similar activity at a bare Au(1 1 1) electrode, whereas Ru and Pt ad-atoms showed a considerable decrease in oxidation current. Pd ad-atoms gave negative catalytic activity. Double layer capacitance measurements revealed that the shift of the potential of zero charge (pzc) between bare Au(1 1 1) and Ag ad-atom modified Au(1 1 1) electrodes (the pzc shifted negatively by modification of Ag) was of great help in the explanation of the observed catalytic activities, where the number of AuOH sites on the Au(1 1 1) surface would be important for the oxidation of glucose and gluconolactone.

Surface functions of modified electrodes for the rapid electron transfer of cytochrome c have been examined by using new surface modifiers. 2-Mercaptopyrazine (2-PyZSH) and 2-mercaptoquinoxaline (or 2-mercaptobenzopyrazine, 2-MQ) modified Au(111) electrodes gave well-defined cyclic voltammmograms of cytochrome c, while a 2-mercaptopyridine (2-PySH) modified electrode gave no response. The STM images of 2-PySH and 2-PyZSH modified surfaces were similar to each other, suggesting 2-PySH and 2-PyZSH adsorbed at both thiolate S and pyridine (or pyrazine) N atoms with pyridine (or pyrazine) ring being perpendicular to the electrode surface. The 2-PyZSH modified surface has another pyrazine N atom faced to the solution, through which cytochrome c can interact, and the double layer capacitance data of the electrode gave more hydrophilic nature than the 2-PySH modified surface. On the other hand, although 2-MQ was suggested to adsorb on the electrode in a similar manner to 2-PySH and 2-PyZSH to give N atom at the solution side, the 2-MQ modified surface showed less hydrophilicity than the 2-PySH modified surface due to the quinoxaline ring. These results clearly reveal that the pyridine and pyrazine N atoms faced to the solution (rather than the hydrophilicity of the electrode surface) are important for the rapid electron transfer of cytochrome c on these modified electrodes. Keywords: Surface function, Surface modifier, Au single crystal electrodes, STM image, Cytochrome c, Cyclic voltammetry

The electrochemical oxidation of 2,6-diaminopurine (2,6-DAP) was studied in pH 7.4 phosphate buffer solution on multiwall carbon nanotube modified glassy carbon electrode (MWCNT/GCE) over a temperature range of 20 to 50 °C using cyclic voltammetry. 2,6-DAP oxidation on MWCNT/GCE showed a well-defined and irreversible oxidation peak at about 0.72 V vs. Ag/AgCl at pH 7.4. The oxidation potential of 2,6-DAP linearly varied with pH over the range of 3.0 to 10.0 with a slope of --0.0547 V/pH, implying that 2 protons were accompanied by 2 electrons transferred in the electrochemical reaction. The activation energy, Ea, of oxidation reaction was found to be 33.10 \pm 1.88 kJ/mol. The differential pulse voltammetric determination of 2,6-DAP was also studied. The peak currents increased linearly with increasing of the 2,6-DAP concentration range from 0.4 m mol/L to 80 m mol/L. The linear regression equation appeared as Ip/mA = --(1.66 \pm 0.42) + (4.21 \pm 0.11) [2,6-DAP]/m mol/L, R2 = 0.9982, and the detection limit (S/N = 3) was 3 \times 10-7 \pm 0.015 mol/L (n =3). The electrocatalytic oxidation of 2,6-DAP on MWCNT/GCE showed that acid pretreated multiwall carbon nanotube can be used in new applications in electrochemical determinations of biologically important compounds.

Multiwalled carbon nanotubes (MWCNTs) were functionalized with acid treatment and thereafter gold-copper nanoparticles were electrodeposited on the MWCNTs by applying several repetitive scans, thus forming a Cu-Au-MWCNT/GCE interface. The electrochemical reduction of oxygen was studied on this modified electrode in 0.1 M NaOH solution. The electrocatalytic activity on the Cu-Au-MWCNT/GCE showed a tendency towards the O-2 reduction. The peak potential of O-2 reduction on the Cu-Au-MWCNT/GCE shifted ca. 70 mV higher positive potentials as compared to that of a polished glassy carbon electrode. A significant current enhancement was obtained on the Cu-Au-MWCNT/GCE compared to that of bare GCE, MWCNT/GCE, Cu-MWCNT/GCE and Au-MWCNT/GCE. Scanning electron microscopy (SEM) and X-ray photoelectron spectroscopy (XPS) were employed in order to investigate the surface morphology and elemental composition of the modified electrode, respectively. (C) 2011 Elsevier B.V. All rights reserved.

Electrocatalytic reduction of oxygen at electrochemically deposited Pt ad-layer modified Au(111) electrodes was studied in an O2 -saturated NaOH (0.1 M) solution. The results were compared with those obtained by using a polycrystalline Pt electrode and another Pt-deposited electrode prepared by replacement with Cu on bare Au(111). Linear sweep voltammetry displayed a positive shift of the oxygen reduction potential by about 0.14 V compared to the bare Au(111) electrode. This shift was about 0.06 V compared to a Pt disk electrode. Tafel slopes gradually changed between 0.06 and 0.1 V/dec, from 0.075 to -0.10 V/dec, from lower to higher current density region. The Pt ad-layer clearly served as a catalyst for oxygen reduction via 4-electron transfer. In terms of the desired shift in reduction potential and increased current density, the best electrocatalytic activity was obtained with a 30-s electrodeposited Pt ad-layer modified Au(111) electrode.

The electrochemical oxidation of methanol was investigated by using various ad-layer modified Au(111) electrodes in alkaline media in comparison to Au(111), polycrystalline Pd, and polycrystalline Pt electrodes. Catalytic activity of gold toward methanol oxidation has tended to increase in more alkaline media, as reflected in the oxidation peak in the concentration range of NaOH (0.1-3.0 M) studied here. The oxidation peak potential of methanol shifted to more negative potentials, indicating a pH-dependent surface reaction. Among the electrodes studied, single-crystal gold electrode surfaces modified with Pd and Pt ad-layers displayed the highest catalytic activity for methanol oxidation. Additional shifts of about 350 mV in the oxidation peak potential of methanol was observed for both ad-layer modified electrodes to more negative potentials compared to that of bare electrodes. The Pd and Pt ad-layer modified Au(111) electrode surfaces did not only supply a superior electrical contact, but also accelerated electron transfer, as shown by the increase in peak current and the positive shift in peak potential. This effect was supported by the doublelayer capacitance measurements of bare Au(111) and Pd ad-layer modified singlecrystal electrodes where the potential of zero charge changed from 15 to 5 mV.

The electrochemical oxidation of borohydride was investigated by using various ad-atom modified Au(111) electrodes in alkaline media in comparison to Au(111) single crystal, polycrystalline Au, Pt and Zn electrodes. The catalytic activity of gold towards borohydride oxidation has tended to increase in more alkaline media as reflected in the oxidation peak in the concentration range of NaOH (0.01-2.0 M) studied. Additional shift on the oxidation peak potential of borohydride on Pt and Zn ad-atom modified Au(111) electrodes was observed for both ad-atom modified electrodes to more negative potentials compared to that of bare electrodes, respectively. The ad-atom modified Au(111) electrodes surfaces do not only provide a superior electrical contact, but also accelerates electron transfer as proven by the increase in peak current and positive shift in the peak potential. Copyright (C) 2011, Hydrogen Energy Publications, LLC. Published by Elsevier Ltd. All rights reserved.

Ethanol oxidation wasstudied on single-crystalAu(111) electrodes that weremodified byplatinum, palla-dium, and cadmium metal ad-layers. The metal ad-layer modification was carried out by the underpotentialdeposition process, in which controlled amounts of Pt, Pd, and Cd were electrodeposited onto the substrateas submonolayer or monolayer coverage. The activity of the metal ad-layer modified Au(111) electrodestoward ethanol oxidation was studied in alkaline media, and recorded voltammograms were compared tothose of bare single crystal Au(111) and polycrystalline gold and platinum disk electrodes. In terms ofthe desired shift in reduction potential and increased current density, the best electrocatalytic activity wasobtained with a 30-s electrodeposited Pt ad-layer modified Au(111) electrode.Key Words: Ethanol oxidation, Pt ad-layer, Pd ad-layer, Cd ad-layer, Au(111) single crystal electrode,fuel cell, catalyst

A stable electroactive thin film of poly-hematoxylin (poly-HT) was successfully prepared on a glassy carbon electrode (GCE) surface by recording successive cyclic voltammograms of 0.3 mM HT, in a phosphate buffer solution (pH 7.0) containing 0.1 M NaNO3, in the potential range of -0.5 to +2.0 V vs. Ag/AgCl. The deposition of HT on GCE surface can be explained through the electropolymerization process. This poly-HT modified electrode exhibited a good electrocatalytic activity towards the NADH oxidation in a phosphate buffer solution (pH 7.0), and led to a significant decrease in the overpotential by more than 320 mV compared with the bare GCE. In order to perform the photoelectrocatalytic determination of NADH in a flow injection analysis (FIA) system, a home-made flow electrochemical cell with a suitable transparent window for irradiation of the electrode surface was constructed. Flow rate of carrier solution, transmission tubing length, injection volume and applied potential for the amperometric and photoamperometric FIA studies were optimized as 1.3 mL min(-1),10 cm, 100 mu L and +300 mV vs. Ag/AgCl, respectively. The currents obtained from amperometric and photoamperometric measurements in FIA system at optimum conditions were linearly dependent on the NADH concentration and linear calibration curves were obtained in the range of 1.0 X 10(-7)-1.5 X 10(-4) M and in the range of 1.0 x 10(-7)-2.5 X 10(-4) M NADH, respectively. The relative standard deviation (RH)) of six replicate injections of 6.0 x 10(-5) M NADH was calculated as 2.2% and 4.3% for the amperometric and the photoamperometric method, respectively. The limit of detection was found to be 3.0 x 10(-8) M for the photoamperometric determination of NADH. (C) 2010 Elsevier B.V. All rights reserved.

Cu nanoparticles have been electrochemically incorporated polypyrrole film that was used for modification of the glassy carbon electrode surface. The performance of the electrode has been characterized by cyclic voltammetry and atomic force microscopy. The electrode has shown high electrocatalytic activity towards the oxidation of dopamine (DA) and uric acid (UA) simultaneously in a phosphate buffer solution (pH 7.00). The electrocatalytic oxidation currents of UA and DA were found linearly related to concentration over the range 1x10(-9) to 1x10(-5)M for UA and 1x10(-9) to 1x10(-7)M for DA using DPVs method. The detection limits were determined as 8x10(-10)M (s/n=3) for UA and 8.5x10(-10)M (s/n=3) for DA at a signal-to-noise ratio of 3.

A single-crystal Au(111) electrode was used for the simultaneous determination of dopamine (DA) and ascorbic acid (AA) in a phosphate buffer solution at pH 6.9. The single-crystal Au(111) electrode displayed excellent electrocatalytic activity for DA and AA oxidation in comparison to a Au disk electrode. Although the anodic peaks of both reagents overlapped on the Au disk electrode, the anodic peak potentials of DA and AA in their mixture were well separated since the peak potential of AA was shifted to more negative values by cyclic and differential pulse voltammetry. The oxidation peak current increased linearly with the concentration of DA in the range of 5 \times 10-6-5 \times 10-4 mol/L in the presence of 5 \times 10-4 mol/L AA. The detection limit of DA was 5 \times 10-7 mol/L. The peak current also linearly increased with increasing AA concentration in the presence of 5 \times 10-4 mol/L DA in the range of 1 \times 10-6-5 \times 10-4 mol/L. The detection limit of AA was 5 \times 10-8 mol/L (s/n = 3). The single-crystal Au(111) electrode showed excellent electrocatalytic activity to both AA and DA, probably because hydrogen flame treatment made the single-crystal electrode surface a well-defined atomic structure.

Background: The purpose of this study is to evaluate the nephrotoxicity of sevoflurane inhalation anesthesia applied during carbon dioxide pneumoperitoneum ( CO2-PNP) which is conducted for a laparoscopic surgery treatment. Materials and Methods: 14 New Zealand white rabbits were used in this study. Initially, anesthesia was induced using 3.7% concentrated sevoflurane + 50% O-2/N2O. Then, a tracheotomy was performed, and the rabbits were mechanically ventilated. The first group ( n = 7) was subjected to CO2-PNP for 90 min with a constant intraabdominal pressure of 12 mm Hg, the second ( control group) ( n = 7) was exempted. The serum inorganic fluoride ( IF-) concentration was measured. The rabbits were sacrificed after 72 h, and one kidney each was immediately extracted for histopathological examination. Results: Serum IF- concentrations were not different in both groups. Histopathologically, mild renal damage was found in one rabbit in each group. Conclusion: CO2-PNP did not have any additional effect on the nephrotoxicity of sevoflurane.

WOS: 000380707100007, PubMed ID: 30460294, Ammonia borane is widely used in most areas including fuel cell applications. The present paper describes electrochemical behavior of ammonia borane in alkaline media on the poly(p-aminophenol) film modified with Au and Ag bimetallic nanoparticles. The glassy carbon electrode was firstly covered with polymeric film electrochemically and then, Au, Ag, and Au-Ag nanoparticles were deposited on the polymeric film, respectively. The surface morphology and chemical composition of these electrodes were examined by scanning electron microscopy, transmission electron microscopy, electrochemical impedance spectroscopy, X-ray diffraction, and X-ray photoelectron spectroscopy. It was found that alloyed Au-Ag bimetallic nanoparticles are formed. Electrochemical measurements indicate that the developed electrode modified by Au-Ag bimetallic nanoparticles exhibit the highest electrocatalytic activity for ammonia borane oxidation in alkaline media. The rotating disk electrode voltammetry demonstrates that the developed electrode can catalyze almost six-electron oxidation pathway of ammonia borane. Our results may be attractive for anode materials of ammonia borane fuel cells under alkaline conditions., Scientific and Technical Research Council of Turkey (TUBITAK)Turkiye Bilimsel ve Teknolojik Arastirma Kurumu (TUBITAK) [110T806]; EBILTEMEge University [BIL-012]; Ege University Research Funds (BAP project)Ege University [10 FEN/075], This work was supported by the Scientific and Technical Research Council of Turkey (TUBITAK) with 110T806 project number, EBILTEM with BIL-012 project number, and Ege University Research Funds (BAP project, 10 FEN/075). The author thanks the Associate Prof. Dr. Armagan Kinay for his careful reading of the manuscript.