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Öğe 1, 10- Fenantrolin Mono Hidrat'ın Elektrokimyasal Modifikasyonu ve Karakterizasyonu(Selçuk Üniversitesi Fen-Edebiyat Fakültesi, 2008) Öztekin, Yasemin; Yazıcıgil, ZaferBu çalışmada, 1, 10- Fenantrolin Mono Hidrat'ın (F) sulu ve susuz ortamda Camsı Karbon elektrot (GC) yüzeyinde elektrokimyasal davranışları dönüşümlü voltametri tekniği ile incelenmiştir.Öğe 1,10-Phenanthroline Derivatives as Mediators for Glucose Oxidase(Elsevier Advanced Technology, 2010) Öztekin, Yasemin; Krikstolaityte, Vida; Ramanaviciene, Almira; Yazıcıgil, Zafer; Ramanavicius, ArunasThis study is focused on possible application of some 1,10-phenanthroline derivatives (PDs) in the development of biosensors and biofuel cells Differently from some other studies, the PDs that were not involved into structures of metal complexes were investigated. Five PDs [1,10-phenanthroline monohydrate (PMH), 5-nitro-1,10-phenanthroline (5NP), 5-amino-1,10-phenanthroline (5AP), 5-amino,6-nitro-1.10-phenanthroline (5A6NP) and 5,6-diamino-1,10-phenanthroline (56DAP)] were selected for this study Bioelectrochemical responses of PDs and glucose oxidase (GOX)-modifiecl graphite rod electrodes (GREs) were studied amperometrically and potentiometrically The best redox mediators for GOX were found on PDs containing amino groups SAP and 56DAP Amperometrical measurements have shown that 5NP derivative was also acting as a redox mediator but activity of 5NP was approximately four times lower than 5AP and three times lower than 56DAP This study clearly illustrates that some PDs can be applied as redox mediators for oxidases and are suitable for the development of reagent-less biosensors and biofuel cells. Since amino groups can be very easily involved in the formation of chemical bounds, the amino-PDs are interesting compounds for the development of nanobiotechnological tools by bottom-up technique.Öğe Amperometric Glucose Biosensor Based on Glucose Oxidase, 1,10-Phenanthroline-5,6-dione and Carbon Nanotubes(ELECTROCHEMICAL SOC INC, 2014) Zor, Erhan; Öztekin, Yasemin; Ramanaviciene, Almira; Anusevicius, Zilvinas; Bingöl, Haluk; Barkauskas, Jurgis; Ersöz, MustafaA biosensor for glucose determination was fabricated by the immobilization of glucose oxidase (GOx) on carbon nanotubes (CNTs) and/or 1,10-phenanthroline-5,6-dione (PD) modified graphite rod electrodes (GOx/PD/CNTs/GR) and its amperometric response toward glucose was investigated under aerobic and anaerobic conditions. The sensitivity of the GOx/PD/CNTs/GR electrode was found to be higher compared to that of a PD-modified GR electrode without CNTs (GOx/PD/GR), implying that CNTs play an important role in the facilitation of electron transfer between the redox active site of GOx and the electrode surface. The GOx/PD/CNTs/GR biosensor exhibited a linear dependency on substrate concentration in a range from 0.0 until 50.0 mM of glucose with oxygen present and from 0.0 until 62.5 mM of glucose in the absence of oxygen. With oxygen present, the limit of detection (LOD) values were determined to be 5.4 and 8.0 mM, and the limit of quantitation values (LOQ) were calculated as 16.2 and 24 mM for GOx/PD/GR and GOx/PD/CNTs/GR, respectively. In the absence of oxygen, the LOD values were calculated as 4.2 and 10.7 mM, and the LOQ values were calculated as 12.6 and 32.1 mM for GOx/PD/GR and GOx/PD/CNTs/GR, respectively. When examining the interference effect of uric acid for GOx/PD/GR and GOx/PD/CNTs/GR electrodes, no significant changes in the amperometric response of the modified electrodes were observed up to 100.0 mM of uric acid. (C) 2014 The Electrochemical Society. All rights reserved.Öğe Biofuel Cell Based on Anode and Cathode Modified by Glucose Oxidase(WILEY-V C H VERLAG GMBH, 2013) Krikstolaityte, Vida; Öztekin, Yasemin; Kuliesius, Jurgis; Ramanaviciene, Almira; Yazıcıgil, Zafer; Ersöz, Mustafa; Okumuş, AytuğA single compartment biofuel cell (BFC) based on an anode and a cathode powered by the same fuel glucose is reported. Glucose oxidase (GOx) from Aspergillus niger was applied as a glucose consuming biocatalyst for both anode and cathode of the BFC. The 5-amino-1,10-phenanthroline modified graphite rod electrode (GRE) with cross-linked GOx was used as the bioanode, and the GRE with co-immobilised horseradish peroxidase and GOx was exploited as the biocathode of the BFC. The open-circuit voltage of the designed BFC exceeded 450mV and a maximal power density of 3.5 mu W/cm(2) was registered at a cell voltage of 300mV.Öğe Boron Removal by Electrodialysis With Anion-Exchange Membranes(Elsevier Science Bv, 2006) Yazıcıgil, Zafer; Öztekin, YaseminThe removal of boron from an aqueous solution was studied in a two-chamber cell separated with a commercial anion-exchange membrane as a function of current density, pH, type of the membrane, concentration and different type of salt solutions. At the end of these studies, the maximum value of boron removal was obtained under the conditions where the maximum current was applied; 0.1 M H3BO3 (pH = 9) and 0.001 M NaCl solutions were used as a catholyte and an anolyte solution, respectively. The AHA membrane was used for separating the two cells used in the electrodialysis experiments. All experiments were carried out at room temperature, and the concentration of boron at the anode cell was determined by ICP-AES. It was concluded that electrodialysis is an appropriate method for boron removal from aqueous solutions under suitable conditions.Öğe Camsı karbon elektrot yüzeyine çeşitli fenantrolin türevlerinin modifikasyonu, yüzey karakterizasyonu, elektrokimyasal ve spektroskopik özelliklerinin incelenmesi(Selçuk Üniversitesi Fen Bilimleri Enstitüsü, 2008) Öztekin, Yasemin; Yazıcıgil, ZaferBu tez çalışmasında, 1, 10?Fenantrolin türevlerinin sulu ve susuz ortamda Camsı karbon elektrot (GC) yüzeyinde elektrokimyasal davranışları dönüşümlü voltametri tekniği ile incelenmiştir. Sulu ortam çalışmalarında farklı pH'larda Britton Robinson (BR) tamponu kullanılırken, susuz ortam çalışmalarında asetonitrilde (ACN) 0.1 M olacak şekilde hazırlanmış tetrabütilamonyum tetrafloraborat (TBATFB) çözeltisi tercih edilmiştir. Yüzey modifikasyon deneyleri +1.2/+2.7 V potansiyel aralığında, 100 mV/s tarama hızında, 30 döngülü olarak gerçekleştirilmiştir. Her iki ortamda da elde edilen yüzeylerin dönüşümlü voltametri tekniği ile redoks problar varlığında elektrokimyasal olarak ve elektrokimyasal impedans spektroskopisi tekniği ile spektroskopik olarak ayrıca susuz ortamda elde edilen yüzeylerin temas açısı ve elipsometri teknikleriyle yüzey karakterizasyonları yapılmıştır. Elde edilen yüzeyler metal tutuculukları, metallerin ayrılması ve biyomateryallere karşı ilgileri bakımından karşılaştırılmış ve bu uygulama alanlarında değerlendirilmişlerdir.Öğe The Comparison of Two Different Electro-Membrane Processes' Performance for Industrial Applications(WILEY-V C H VERLAG GMBH, 2010) Öztekin, Yasemin; Yazıcıgil, Zafer; Ata, Nejla; Karadayı, NerimanThe recovery of bases from solutions containing salt forms of potassium was studied in cells separated by commercial ion exchange membranes. For this aim, two different types of techniques were applied. In the first technique, an equimolar quantity of acid solutions and different metallic salt solutions were used as an anolyte and a catholyte, respectively, in the cell separating with anion exchange membrane (AEM). In the second technique, an equimolar quantity of acid, base solutions, and different metallic salt solutions were used as an anolyte, a catholyte, and a solution in the middle chamber of the cell, respectively, in the cell separating with cation exchange membrane (CEM) and AEM. Effects of the current, the type of the membranes, the concentrations of the solutions, and the type of solutions on the recovery of bases were investigated and both of the techniques were compared. The results of the experiments were evaluated with the Statistical Package for Social Sciences program.Öğe Electrochemical determination of Cu(II) ions using glassy carbon electrode modified by some nanomaterials and 3-nitroaniline(ELSEVIER SCIENCE BV, 2015) Dedelaite, Lina; Kızılkaya, Selin; İncebay, Hilal; Çiftçi, Hakan; Ersöz, Mustafa; Yazıcıgil, Zafer; Öztekin, YaseminThe aim of this research was to investigate the effect of the several nanomaterials in electrochemical determination of Cu(II) ions. For this aim, firstly the deposition of graphene oxide (GO), graphene, magnetite (Fe3O4), gold-chitosan (AuChts) or multilayer carbon nanotubes (MWCNTs) on the glassy carbon (GC) electrode surface was performed. Then the electrochemical modification of electrode by poly-3-nitroaniline (poly-3NA) was performed by 100 potential cycles in the range between +0.9 V and +1.4 V vs. Ag/AgNO3 at the sweep rate of 100 mV/s. For electrochemical reduction of nitro groups present on modified GC electrode surface, potential cycling was performed in 100 mM HCl between -0.1 V and -0.8 V vs. Ag/AgCl/(KClsat.) at the sweep rate of 100 mV/s. Nanomaterial and poly-3NA modified electrodes were applied in the determination of Cu(II) ions by differential pulse voltammetry. It was determined that GC electrodes consecutively modified with MWCNTs, poly-3NA and then by electrochemical reduction of nitro groups were the most sensitive towards Cu(II) ions with detection limit of 0.5 x 10(-9) M. (C) 2015 Elsevier B.V. All rights reserved.Öğe Electrochemical Modification of Glassy Carbon Electrode by Poly-4-Nitroaniline and Its Application for Determination of Copper(II)(Pergamon-elsevier Science Ltd, 2010) Öztekin, Yasemin; Tok, Mutahire; Nalvuran, Hande; Kıyak, Saliha; Göver, Tuğçe; Yazıcıgil, Zafer; Ramanaviciene, Almira; Ramanaviciusi, ArunasElectrochemical modification of glassy carbon (GC) electrode by poly-4-nitroaniline (P4NA), electrochemical reduction of P4NA and applicability of electrode modified in this way for determination of copper(II)(Cu(II)) is reported in this study. Electrochemical surface modification was performed by cyclic voltammetry in the potential range between +0.9V and +1.4V vs. Ag/Ag+ (in 10 mM AgNO3) at the scan rate of 100 mV/s by 100 cycles in non-aqueous media. In order to provide electrochemical reduction of nitro groups on the P4NA-modified GC electrode surface (P4NA/GC), the cyclic voltammograms inducing/evidencing the reduction of nitro groups were performed in the potential range between -0.1 V and -0.8 V vs. Ag/AgCl/(sat.KCI) at the scan rate of 100 mV/s. The reduced P4NA/GC surfaces (Reduced-P4NA/GC) were treated with aqueous solution of nitrilotriacetic acid. The sensitivity of GC electrode modified in described way towards Cu(II) was investigated in Britton-Robinson buffer solution, pH 5.0. The potentiometric generic pulse technique was applied as innovative electrochemical method for detection of analytical signal. It was shown that GC electrodes modified in here described way will be suitable for the determination of Cu(II) in technological waste water and/or some other solutions containing Cu(II) ions.Öğe Etilendiamin Tetraasetik Asit Varlığında Yeni Yüzeylerin Hazırlanması, Karakterizasyonu ve Metal Sensör Olarak Uygulanabilirliği(Selçuk Üniversitesi Fen Fakültesi Fen Dergisi, 2016) Nilüfer, Şükriye; Öztekin, YaseminKarbon elektrot yüzeyinin modifikasyonu sayesinde metal tayini uygulamalarında gelecekte gelişmelere ön olabileceğine inanılan bu çalışma, camsı karbon elektrot yüzeyinin etilendiamin tetraasetik asit ile modifikasyonunu ve modifiye yüzeylerin bakır (II) iyonunun tayini üzerine uygulamalarını kapsamaktadır. Yalın ve modifiye elektrot yüzeyleri redoks problar varlığında dönüşümlü voltametri tekniği ve taramalı elektron mikroskobu ile karakterize edilmiş ve veriler birbirleriyle karşılaştırılmıştır. Etilendiamin tetraasetik asitmodifiye camsı karbon elektrot yüzeyinin pH’ı 3.0 olan Britton-Robinson tampon çözeltisindeki bakır (II) iyonlarına karşı yüksek hassasiyette ve nikel (II), demir (III) ve kobalt (II) iyonları varlığında yüksek seçicilikte olduğu tespit edilmiştir.Öğe Salt Splitting Process Application(Desalination Publ, 2010) Öztekin, Yasemin; Karadayı, Neriman; Yazıcıgil, ZaferThe recovery of bases from solutions containing metallic salts were achieved in three compartment cells separated with commercial ion exchange membranes (IEMs) as anion exchange membrane (AEM) and cation exchange membrane (CEM). In the experiments, an equimolar quantity of acid, base and different salts of metal solutions were used as the anolyte and the catholyte solutions and the solution in the middle chamber of the cell, respectively. Effects of current, the type of ion-exchange membranes, the nature and the concentrations of the solutions on the recovery of bases were investigated. The results of the experiments were analyzed with the statistical package for social sciences (SPSS) program. The results obtained show that electrohydrolysis seems to be an applicable method for the recovery of bases from waste water at suitable conditions.Öğe Separation of Nickel From Cobalt Using Cation Exchange Membranes in the Presence of Chelating Agents(Desalination Publ, 2010) Öztekin, Yasemin; Yazıcıgil, Zafer; İnce, A. KadirSelectivity of metals from aqueous solutions containing chelating agents such as EDTA (ethylenediaminetetraacetic acid), NTA (nitrilotriacetic acid) and citrate was studied in a two-chamber cell separating with a commercial cation-exchange membrane (CEM). In the experiments, equimolar solutions of metal and chelating agent as an anolyte and acid solutions as a catholyte were used, the effect of current density, type of solvent, concentration of catholyte and anolyte solution, type of chelating agent, type of the cation-exchange membrane on the selectivity for metals were determined. The obtained results show that this membrane technique, classified as electrodeposition and electrodialysis, seems to be an applicable method for the selectivity of metals under appropriate conditions.
