Zekerya Dursun

Cu nanoparticles incorporated polypyrrole modified GCE for sensitive simultaneous determination of dopamine and uric acid

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.

Voltammetric behavior of copper(I)oxide modified carbon paste electrode in the presence of cysteine and ascorbic acid

The electrochemical behavior of a copper(I)oxide (Cu(2)O) 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 -0.65V 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 -0.07V in phosphate buffer at pH 6.9. Linear responses were observed in the range 2.0x10(-9) to 3.0x10(-8)M with a 0.9954 correlation coefficient for RS and 1.0x10(-9) to 2.0x10(-8)M with a 0.9961 correlation coefficient for AA.

Photoelectrocatalytic oxidation of NADH in a flow injection analysis system using a poly-hematoxylin modified glassy carbon electrode

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 μL 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 1.0×10(-7)-1.5×10(-4) M and in the range of 1.0×10(-7)-2.5×10(-4) M NADH, respectively. The relative standard deviation (RSD) of six replicate injections of 6.0×10(-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 3.0×10(-8) M for the photoamperometric determination of NADH.

Polymer Film Supported Bimetallic Au–Ag Catalysts for Electrocatalytic Oxidation of Ammonia Borane in Alkaline Media

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.Graphical Abstract

Effects of CO2 Pneumoperitoneum on Nephrotoxicity of Sevoflurane: An Experimental Study in Rabbits

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% O2/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.

Simultaneous determination of theophylline and caffeine on novel [Tetra-(5-chloroquinolin-8-yloxy) phthalocyanato] manganese(III)-Carbon nanotubes composite electrode

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 × 10-9 M and 5.0 × 10-8 M, respectively. In simultaneous determination, LODs were calculated for theophylline and caffeine as 8.1 × 10-9 M and 3.0 × 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.

Highly catalytic activity of platinum-gold particles modified poly(p-aminophenol) electrode for oxygen reduction reaction

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.