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Öğe Comparison of electrocatalytic activity of poly(p-aminophenol) Film Supported Au-M (M= Pt, Cu and Ag) bimetallic nanoparticles for oxidation of sodium borohydride(2013) Karabiberoglu S.; Dursun Z.A poly (p-aminophenol) film (PPAP) and bimetallic nanoparticles modified polymer film galssy carbon electrodes (GCE), Au-Pt/PPAP/GCE, Au-Ag/PPAP/GCE and Au-Cu/PPAP/GCE were prepared by electrochemical techniques. The modified electrode surfaces were characterized using scanning electron microscopy (SEM) and energy-dispersive X-ray spectroscopy (EDX). The electrocatalytic activities of modified PPAP/GC and bulk electrodes were investigated for borohydride oxidation in alkaline media and the response of electrodes were compared with each other from the corresponding voltammetric curves. There was no any oxidation take place on bare GCE, PPAP/GCE and Cu/PPAP/GCE in the presence of sodium borohydride. Au-Pt bimetallic modified PPAP/GGCE showed higher catalytic activity toward sodium borohydride in terms of the manner of both peak potential and peak current.Öğe Cu nanoparticles incorporated polypyrrole modified GCE for sensitive simultaneous determination of dopamine and uric acid(Elsevier, 2010) Ulubay S.; Dursun Z.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 1 × 10-9 to 1 × 10-5 M for UA and 1 × 10-9 to 1 × 10-7 M for DA using DPVs method. The detection limits were determined as 8 × 10-10 M (s/n = 3) for UA and 8.5 × 10-10 M (s/n = 3) for DA at a signal-to-noise ratio of 3. © 2009 Elsevier B.V. All rights reserved.Öğe Effects of CO 2 pneumoperitoneum on nephrotoxicity of sevoflurane: An experimental study in rabbits(2006) Bayar M.S.; Küçükgüçlü S.; Gokmen N.; Dursun Z.; Tuna E.B.; Erkan N.Background: The purpose of this study is to evaluate the nephrotoxicity of sevoflurane inhalation anesthesia applied during carbon dioxide pneumoperitoneum (CO 2-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/N 2O. Then, a tracheotomy was performed, and the rabbits were mechanically ventilated. The first group (n = 7) was subjected to CO 2-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: CO 2-PNP did not have any additional effect on the nephrotoxicity of sevoflurane. © 2006 S. Karger GmbH.Öğe Electroanalysis of caffeic acid in red wine and investigation of thermodynamic parameters using an Ag nanoparticles modified poly(thiophene) film glassy carbon electrode(2013) Karabiberoglu S.U.; Ayan E.M.; Dursun Z.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 4.83×10-6M with a detection limit of 5.3×10-9M (S/N=3). The modified electrode was used for determination of CA concentration in red wine samples. The thermodynamic constants, entropy change (?S), enthalpy change (?H) and Gibbs free energy change (?G) were calculated as -166.34J/(molK), -154.24kJ/mol and -104.75kJ/mol at 25°C, respectively. © 2013 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.Öğe Electrochemical oxidation of ammonia borane on Au-Ag nanoparticles Modified Poly (p-aminophenol) film Glassy Carbon Electrode(2013) Karabiberoglu S.; Dursun Z.An Au-Ag nanoparticles modified poly(p-aminophenol) film electrode (Au-Ag/PPAP/GCE) was prepared by cyclic voltammetry. The electrochemical behaviour of ammonia borane (NH3BH3, AB) was studied in alkaline media at Au-Ag/PPAP/GCE. The surface morphology and chemistry were characterized by scanning electron microscopy (SEM), energy dispersive X-ray spectroscopy (EDX) and CV techniques. There was no any oxidation reaction occurs on bare GCE and PPAP/GCE in the presence of AB. Among the five electrodes which were Au disk, Ag/PPAP/GCE, Au/PPAP/GCE and Au-Ag/PAP/GCE. The comparative studies were revealed that Au-Ag/PPAP/GCE yield the best results due to the highest peak current and shifting the oxidation potential to more negative values for AB oxidation.Öğe Fabrication of Cu?CeO2 Coated Multiwall Carbon Nanotube Composite Electrode for Simultaneous Determination of Guanine and Adenine(Wiley-VCH Verlag, 2018) Aktürk M.; Karabiberoğlu Ş.U.; Dursun Z.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, WeinheimÖğe An over-oxidized poly(Rutin) modified electrode for selective and sensitive determination of catechol and hydroquinone(Elsevier B.V., 2019) Karabiberoğlu Ş.U.; Koçak Ç.C.; Dursun Z.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 5.2 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. © 2019Öğe Polymer Film Supported Bimetallic Au–Ag Catalysts for Electrocatalytic Oxidation of Ammonia Borane in Alkaline Media(SpringerOpen, 2016) Karabiberoğlu Ş.U.; Koçak Ç.C.; Koçak S.; Dursun Z.Abstract: 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: [Figure not available: see fulltext.] © 2016, The Author(s).Öğe Sensitive determination of hydrazine using poly(phenolphthalein), Au nanoparticles and multiwalled carbon nanotubes modified glassy carbon electrode(TUBITAK, 2021) Hatip M.; Koçak S.; Dursun Z.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.Öğe Voltammetric behavior of copper(I)oxide modified carbon paste electrode in the presence of cysteine and ascorbic acid(Elsevier, 2004) Dursun Z.; Nişli G.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. © 2004 Elsevier B.V. All rights reserved.
