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Öğe 1,10-Phenanthroline modified glassy carbon electrode for voltammetric determination of cadmium(II) ions(ELSEVIER SCIENCE SA, 2011) Oztekin, Yasemin; Ramanaviciene, Almira; Ryskevic, Natalija; Yazicigil, Zafer; Ustundag, Zafer; Solak, Ali Osman; Ramanavicius, ArunasThis study reports the electrochemical modification of glassy carbon (GC) electrode surface with the electro-polymerized form of 1,10-phenanthroline monohydrate (PMH), the characterization of this polyphenanthroline modified electrode (PPMH/GC) and the electroanalytical application suitable for the determination of Cd(II) ions. The PPMH/GC electrode was characterized by cyclic voltammetry, chronoamperometry and atomic force microscopy and formation of polyphenanthroline layer grafted to surface of GC electrode was evidenced. Selectivity of PPMH/GC electrode towards heavy metal ions was investigated by square wave voltammetry. The PPMH/GC electrode was found to be suitable for selective determination of Cd(II) in the solutions containing the mixture of heavy metal ions and showed high stability and reproducibility. The analytical methodology was successfully applied for monitoring the toxic metal ions in real samples. (C) 2011 Elsevier B.V. All rights reserved.Öğe Copper nanoparticle modified carbon electrode for determination of dopamine(PERGAMON-ELSEVIER SCIENCE LTD, 2012) Oztekin, Yasemin; Tok, Mutahire; Bilici, Esra; Mikoliunaite, Lina; Yazicigil, Zafer; Ramanaviciene, Almira; Ramanavicius, ArunasThis paper reports the synthesis and characterization of copper nanoparticles (CuNPs) and application of copper nanoparticle-modified glassy carbon electrode for the electrochemical determination of dopamine. Electrochemical measurements were performed using differently modified glassy carbon (GC) electrodes. Bare, oxidized before modification and copper nanoparticle-modified glassy carbon electrodes (bare-GC, ox-GC and CuNP/GC electrodes, respectively) were characterized by cyclic voltammetry and electrochemical impedance spectroscopy in the presence of redox probes. Atomic force microscopy was used for the visualization of electrode surfaces. The CuNP/GC electrode was found to be suitable for the selective determination of dopamine even in the presence of ascorbic acid, uric acid, and p-acetamidophenol. The observed linear range of CuNP/GC for dopamine was from 0.1 nM to 1.0 mu M while the detection limit was estimated to be 50 pM. It was demonstrated that here reported glassy carbon electrode modified by copper nanoparticles is suitable for the determination of dopamine in real samples such as human blood serum. (C) 2012 Elsevier Ltd. All rights reserved.Öğe Direct electron transfer from glucose oxidase immobilized on polyphenanthroline-modified glassy carbon electrode(ELSEVIER ADVANCED TECHNOLOGY, 2011) Oztekin, Yasemin; Ramanaviciene, Almira; Yazicigil, Zafer; Solak, Ali Osman; Ramanavicius, ArunasThis study reports direct electron transfer (DET) from immobilized glucose oxidase (GOx) via grafted and electropolymerized 1,10-phenanthroline monohydrate (PMH). The layer of poly-1,10-phenanthroline (PPMH) was gained via electrochemical deposition, which was used to create the PPMH-modified GC-electrode (PPMH/GC-electrode). Further, the GOx was immobilized on the PPMH/GC-electrode. The effect of surface-modification by the PPMH on the electron-transfer between enzyme and electrode-surface and some other electrochemical/analytical-parameters of newly designed enzymatic-electrode were evaluated. The PPMH/GC-electrode showed superior DET to/from flavine adenine dinucleotide cofactor of GOx, while some redox-compounds including ferrocene and K-3[Fe(CN)(6)] were completely electrochemically inactive on the PPMH/GC-electrode. It was also found that the resulting GOx/PPMH/GC-electrode functioned as a "direct response type" glucose-biosensor. The biosensor showed excellent selectivity towards glucose and demonstrated good operational-stability. According to our best knowledge, this study is the first scientific report on electrochemical-polymerization of PMH on the GC-electrode in non-aqueous media followed by its application in the design of glucose-biosensor. (C) 2010 Elsevier B.V. All rights reserved.Öğe Effect of different copper salts on the electrochemical determination of Cu (II) by the application of the graphene oxide-modified glassy carbon electrode(ELSEVIER, 2017) Incebay, Hilal; Yazicigil, ZaferIn this study, graphene oxide and reduced graphene oxide nanoparticles were synthesized by Hummers method and characterized Fourier transform infrared spectroscopy, X-ray diffraction spectroscopy, scanning electron microscopy and thermogravimetric analysis. Then, glassy carbon electrode surfaces were modified with synthesized and characterized graphene oxide (GO) and reduced graphene oxide (red-GO) using physical immobilization. Bare and modified surfaces were characterized by cyclic voltammetry, electrochemical impedance spectroscopy and scanning electron microscopy. Application of graphene oxide (GO/GC) and reduced graphene oxide-modified glassy carbon (red-GO/GC) surfaces for the electrochemical determination of copper(II) using different copper salts such as CuSO4 center dot 5H(2)O, Cu(NO3)(2)center dot 3H(2)O and CuCI2 were performed by differential pulse voltammetry. The GO/GC surface was found to be suitable for selective determination of Cu(II) in the solutions containing the mixture of heavy metal ions (Zn(II), Pb(II), Cd(II), Fe(III) and Mn(II)) and showed high stability and reproducibility. The GO/GC surface was treated with CuSO4 center dot 5H(2)O, Cu(NO3)(2)center dot 3H(2)O and CuCI2 salts solution in optimum conditions and afterward SEM images were measured 10 mu m in size and radius of these ions in Cu (II)/GO/GC surfaces. Thus the determination of copper ions on the GO/GC surface was made for the first time by comparing the effect of the types of copper salts. When it was evaluated in terms of inorganic theory, the results were found to be in harmony.Öğe Electrochemical determination of copper(II) using modified glassy carbon electrodes(DESALINATION PUBL, 2012) Bilici, Esra; Yazicigil, Zafer; Tok, Mutahire; Oztekin, YaseminElectrochemical modification of glassy carbon (GC) electrode surface via electrochemical oxidation of 1-aminoindan in acetonitrile including 100.0 mM of tetrabutylammonium tetrafluoroborate and applicability of electrode modified in this way for electrochemical determination of copper(II) (Cu(II)) were reported in this study. Electrochemical surface modification was performed by cyclic voltammetry in the potential range between +0.9 and +1.5V vs. Ag/Ag+ (10.0 mM of AgNO3) at the scan rate of 100 mV/s by 30 potential cycles. The modified electrode surface was characterized by cyclic voltammetry, electrochemical impedance spectroscopy and contact angle measurement. The characterization results were compared with the characterization results of bare GC electrode. The results of the amperometric measurements of the modified GC electrode towards Cu(II) ions were investigated. It was determined that the modified electrode surface had electrochemical responses towards Cu(II) ions with high sensitivity, good selectivity, stability, reproducibility and repeatability. According to the results, it is believed that it will be possible to find an application area for this new surface in any industrial fields.Öğe The electrochemical investigation of salts partition with ion exchange membranes(ELSEVIER SCIENCE BV, 2008) Ata, Nejla; Yazicigil, Zafer; Oztekin, YaseminThe regenaration of acid and base from the solutions containing metallic salts was achieved by salt splitting method (SSM) using not only anion-exchange membranes (AEM) but also cation-exchange membrane (CEM). In these experiments, while the ion exchange membrane was anion-exchange membrane, acid solutions were used as an anolyte and different salts of potassium were used as a catholyte. In addition to these experiments, while the ion exchange membrane was cation-exchange membrane, base solutions were used as a catholyte and different salts of potassium were used as an anolyte. The effects of current density, initial concentrations of anolyte and catholyte solutions, the type of salt solution and the type of the ion-exchange membranes on the recovery ratio of bases and acids were investigated. The results of the experiments were investigated with the Statistical Package for Social Sciences (SPSS) program. The obtained results show that this technique can be used not only for recovering the acid and base wastes of industry but also for removing the impurities in order to obtain pure acids and bases in laboratory conditions. (c) 2008 Elsevier B.V. All rights reserved.Öğe Electrochemical study of 6-(ferrocenyl)hexanethiol on gold electrode surface in non-aqueous media(ELSEVIER, 2018) Gover, Tugce; Yazicigil, ZaferThe electrochemical modification of gold (Au) electrode with 6-(ferrocenyl)hexanethiol (6FcHT) is examined by using of cyclic voltammetry technique in the potential range - 0.2 V/ + 0.5 V at the scan rate of 100 mV/s at 30 cycles in non-aqueous Electrochemical measurements were performed at different Au electrode surfaces. Bare and 6-(ferrocenyl)hexanethiol-modified gold electrodes (bare-Au and 6FcHT/Au electrodes, respectively) were characterized by four methods which are cyclic voltammetry and electrochemical impedance spectroscopy, scanning electron microscopy (SEM), contact angle measurement (CAM). This study, in which electrochemical studies of 6-(ferrocenyl) hexanethiol were carried out in non-aqueous medium showed very little adsorbed of thiol group on gold electrode surface.Öğe Investigation of synthesis of copolymers from the waste products of industrial oil refinement having adhesion properties and strength to the thermal destruction(SPRINGER/PLENUM PUBLISHERS, 2006) Yazicigil, Zafer; Ahmetli, Gulnare; Kara, Huseyin; Kocak, AhmetIn this study, the waste products of industrial vegetable oil refinement were transformed into the glycidyl ester for preventing the effects of them to the environment, the ways for evaluating them in polymer chemistry were investigated, copolymers having high adhesion property and strength to the thermal destruction were synthesized and the area of their usage was determined. For this reason, the waste product of sunflower oil refination as a vegetable oil in the industry; soap stock (SS) was converted to the unsaturated glycidyl esters by the interaction with epichlorohidrine in the alkaline medium. After that the copolymerization of synthesized unsaturated glycidyl esters and the other waste product of oil refinement fatty acid (FA) with styrene in the radicalic initiator medium were investigated and copolymers that have high strength to the thermal destruction and adhesion property were synthesized. From the results of TGA and DTA analysis, it was determined that synthesized copolymers have low loss of weight at high temperature. The structures of copolymers were fixed by spectral and chemical analysis methods.Öğe Investigation of the separation of metal mixtures using cation-exchange membranes(ELSEVIER SCIENCE BV, 2009) Yazicigil, Zafer; Oztekin, YaseminThe process, called electrodeposition, was used for recovery of metals from aqueous solutions. The aqueous solutions of the sulfate forms of copper and cobalt metals were used as the catholyte solution and 0.1 M NaNO3 was used as an anolyte solution. The effect of current density, metal concentration and type of the cation-exchange membrane to the recovery of metals were investigated, optimum conditions were obtained and % recovery value (%R) for each metal was calculated. At the end of this study, it was observed that, in general, for each metal the recovery of metal increased with current density and concentration. On the other hand, it was determined that %R value increased in the order of CMB >CMX >CMS membrane type. All experiments were carried out at room temperature and the concentration of metals was determined with an atomic absorption spectrophotometer.Öğe Investigation to Sensitive Determination of Glucose Using a Hybrid System Based on Graphene and Nickel Nanoparticles(IEEE, 2017) Incebay, Hilal; Bilici, Esra; Yazicigil, ZaferNanoparticles has attracted great attention to many applications due to their extraordinary physical and chemical, mechanical, magnetic, optical, electrical and piezoelectric properties compared to bulk materials, which offer great promise in the development of nanotechnology to revolutionise the world through promising applications, including industry, agriculture, medicine, public health, and environment. On the other hand graphene has received much attention in the last years as a nanomaterial with many potential applications. In this study, solution of reduced graphene oxide, Ni metal nanoparticles were modified on the glassy carbon electrode surface and then graphene and metal nanaoparticle were formed hybrid systems. The modified electrode surfaces prepared in this way were characterized by electrochemically. The obtained results were compared with the results of bare GC. The prepared electrode surfaces were evaluated electrochemical response against different concentrations of glucose for the non-enzymatic and enzymatic glucose sensors application area.Öğe Kinetics of the copolymerization of alkylene oxides with glycidyl methacrylate(JOHN WILEY & SONS INC, 2007) Ahmetli, Gulnare; Kocak, Ahmet; Yazicigil, ZaferIn the present study, the kinetics of copolymerization reaction of propylene oxide (PO) and butylene oxide (BO) with glycidyl methacrylate (GNLA.) in the presence of BF3 center dot O(C2H5)(2) catalyst were investigated. The kinetic parameters and activation energy of the copolymerization reaction were calculated. The amounts of reacting PO, BO, and GMA during copolymerization were determined by chromatographic method, because the same copolymerization conditions were carried out for them. It was determined that the copolymerization rate of PO (r(0)) and BO (r(0)) was higher than that of GMA, but activation energy (E) of GMA was higher than that of PO and BO. The rate of reaction, the rate constant, and activation energy were calculated from the amount of copolymer obtained with respect to time. The structures of synthesized copolymers were determined by the spectral and chemical analysis methods.Öğe Modification of the epoxy resin with epoxide and ester group containing oligomers and compounds(ESTONIAN ACADEMY PUBLISHERS, 2015) Ahmetli, Gulnare; Yazicigil, Zafer; Soydal, UlkuEpoxy toluene oligomers (ETO) are very important substances due to effective functional groups in their structure and they are especially used as polymer additives that have been synthesized from toluene and epichlorhydrin. Flame-retardant properties of the neat epoxy resin (ER), ETO, and ETO/ER blend thermoset were evaluated by UL94 vertical flammability test. The chlorine atoms in ETO increase the stability of the polymer material against burning. For the synthesis other polymers, first the waste product of the industrial vegetable oil refinement acid oil was transformed into the glycidyl ester (FAGE). Unsaturated oligo(ether-ester) (OEE) was prepared by ring-opening polymerization of the propylene oxide (PO) with FAGE in the presence of cationic catalyst BF3 center dot O(C2H5)(2). Its chemical structure was characterized with FTIR spectroscopy. These polymers, isoamyl methacrylate (AMA) and 1,2-epoxy-hexane-5-en (EH) were used as modifiers in the DGEBA-type epoxy resin. The effects of the modifier structure and amount on the mechanical properties of epoxy were investigated. Tensile strength and Young's modulus of the modified samples were found higher than those of the neat epoxy resin.Öğe Phenanthroline derivatives electrochemically grafted to glassy carbon for Cu(II) ion detection(ELSEVIER SCIENCE SA, 2012) Oztekin, Yasemin; Yazicigil, Zafer; Solak, Ali Osman; Ustundag, Zafer; Okumus, Aytug; Kilic, Zeynel; Ramanaviciene, AlmiraNew sensing platform based on modified glassy carbon (GC) suitable for design of heavy metal-ion sensor is reported in this study. GC-based electrodes were electrochemically modified by poly-5-nitro-1,10-phenanthroline (poly-5NP) and poly-5-amino, 6-nitro-1,10-phenanthroline (poly-5A6NP) layers. Grafting of electrochemically formed poly-5NP and poly-5A6NP layers at the GC electrode surface was confirmed by electrochemical reduction of nitro groups into amine groups. Presence of grafted poly-5NP and poly-5A6NP layers and formation of their reduced forms on the GC electrode surface were verified by cyclic voltammetry, electrochemical impedance spectroscopy, contact angle measurements, ellipsometry and X-ray photoelectron spectroscopy. The applicability of poly-5NP- and poly-5A6NP-functionalized carbon surfaces for the determination of Cu(II) ions was demonstrated by formation of complexes between GC-grafted poly-5NP and poly-5A6NP layers and Cu(II) ions. (C) 2012 Elsevier B.V. All rights reserved.Öğe Polyphenol-modified glassy carbon electrodes for copper detection(ELSEVIER SCIENCE SA, 2011) Oztekin, Yasemin; Yazicigil, Zafer; Ramanaviciene, Almira; Ramanavicius, ArunasThe present work reports the preparation of electrochemically polymerized flavone - luteolin and flavonol - kaempferol modified glassy carbon (GC) electrodes (PolyLut/GC and PolyKae/GC, respectively). Electrochemical polymerization was performed by electrochemical oxidation of luteolin and kaempferol by potential cycling in aqueous media. Cyclic voltammograms of luteolin on the GC electrode indicated one clear oxidation peak at +475 mV, which can be assigned to the oxidation of 3'-hydroxyl and 4'-hydroxyl groups in the B-ring of the luteolin molecule. The cyclic voltammograms of kaempferol on the GC electrode contained two oxidation peaks, one at about +390 mV, which is assigned to the oxidation of 4'-hydroxyl and 3-hydroxyl groups of the B-ring and C-ring of the kaempferol molecule, and second oxidation peak at about +710 mV, which is assigned to the 7-hydroxyl group of the A-ring. The interaction of PolyLut/GC and PolyKae/GC electrodes with copper(II) (Cu(II)) ions were investigated by differential pulse voltammetry (DPV). It was determined that PolyLut/GC and PolyKae/GC electrodes showed sensitivity towards Cu(II) with good reproducibility and stability of analytical signal. The effect of the interfering ions on the voltammetric measurements of Cu(II) was examined. (c) 2010 Elsevier B.V. All rights reserved.Öğe Preparation and characterization of a 1,10-phenanthroline-modified glassy carbon electrode(PERGAMON-ELSEVIER SCIENCE LTD, 2009) Oztekin, Yasemin; Yazicigil, ZaferThis paper describes the grafting of 1,10-phenanthroline (P) molecules on the surface of a glassy carbon (GC) electrode. This modification was carried out in both aqueous and non-aqueous media. Britton Robinson (BR) was used in aqueous experiments at different pHs and tetrabutylammonium tetrafluoroborate (TBATFB), 0.1 M in acetonitrile (ACN) was used in non-aqueous experiments. Surface modification experiments were performed in the +1.2-2.7 V potential range with a scan rate of 100 mV/s and 30 cycles. The presence of P at the GC surface was characterized by cyclic voltammetry (CV), electrochemical impedance spectroscopy (EIS), contact angle measurement (CAM) and ellipsometry. The ability of the complex to modify surfaces was investigated with differential pulse voltammetry (DPV). Crown Copyright (C) 2009 Published by Elsevier Ltd. All rights reserved.Öğe Recovery of acids from salt forms of sodium using cation-exchange membranes(ELSEVIER SCIENCE BV, 2007) Oztekin, Yasemin; Yazicigil, ZaferThe recovery of acids from the solutions containing metallic salts (NaNO3, NaCl, Na2SO4) was achieved by the electrohydrolysis (EHD) method using cation-exchange membranes (CEM). In the experiments, base solutions were used as a catholyte and different salts of sodium were used as an anolyte. The effects of flow rate, current density, initial concentrations of salt and base solutions, the type of salt solution and the type of the cation-exchange membrane on the recovery ratio of acids were investigated. The results obtained show that electrodialysis seems to be an applicable method for the recovery of acids at suitable conditions.Öğe Recovery of Zn (II) from its EDTA complexes by electro-membrane process(DESALINATION PUBL, 2009) Yazicigil, Zafer; Oztekin, Yasemin; Ince, A. KadirFactors affecting the efficiency of electrochemical recovery of Zn (II) from its ethylenediaminetetraacetic acid (EDTA) complexes were systematically examined using three types of cation-exchange membranes in a two compartment electrolysis cell. In these experiments, the catholyte contained an equimolar amount of Zn (II) and EDTA, and the anolyte contained 0.1 M NaNO(3). The platinium and stainless steel were used as an anode and a cathode, respectively. The effect of current densities, metal concentration, the type of the cation-exchange membrane on the recovery of metals were determined. It was found that recovery of Zn (II) increased with increase of current density, concentration of catholyte solution, concentration ratio between metal-chelate and changed with the type of membrane in CMB>CMS>CMX order. The obtained numerical results showed that electrodeposition seems to be applicable method for the recovery of metals under appropriate conditions.Öğe Salt splitting with cation-exchange membranes(ELSEVIER SCIENCE BV, 2007) Yazicigil, ZaferThe regeneration of acid and base from different salt forms of potassium by electrodialysis (ED) method was investigated in a two-compartment membrane electrolysis cell. Three types of commercial cation-exchange membranes (CEMs) were used to recover acids from solutions containing salt forms of metals. In the experiments, base solutions were used as a catholyte and different salts of potassium were used as an anolyte. The effects of flow rate, current density, initial concentrations of salt and base solutions, the type of salt solution and the type of the cation-exchange membrane on the recovery ratio of acids were investigated. The results obtained show that electrodialysis seems to be an applicable method for the recovery of acids at suitable conditions.Öğe Spectroscopic Application of Realgar Using X-ray Fluorescence and Raman Spectroscopy(TAYLOR & FRANCIS INC, 2009) Kadioglu, Yusuf Kagan; Ustundag, Zafer; Yazicigil, ZaferSamples of realgar ore were collected from the hydrothermal products of the Eocene volcanic material of the Erzurum region in Turkey. The prepared samples were analyzed by polarized energy dispersive X-ray fluorescence (PEDXRF) and by confocal Raman spectroscopy (CRS). The goal of this study was to figure out the chemical composition of realgar and its properties through PEDXRF and CRS and the optical characteristic features under the polarized microscope. The result of the XRF analysis shows the collected realgar samples are mainly composed of As, S, Si, and Mg in different proportions. The contents of As in realgar change from 36.55% through 31.49% to 5.97% in the analyzed samples. The strong peak of the realgar samples is at 352cm-1, and a weaker peak exists around 190cm-1. The accuracy and precision of the technique for chemical analysis is demonstrated by analyzing CRM 2126-81. The realgar ores were studied by use of CRS and polarized microscopy.Öğe Square wave voltammetry based on determination of copper (II) ions by polyluteolin- and polykaempferol-modified electrodes(ELSEVIER SCIENCE BV, 2011) Oztekin, Yasemin; Yazicigil, Zafer; Ramanaviciene, Almira; Ramanavicius, ArunasApplicability of square wave voltammetry for the determination of Cu(II) ions by PolyLut/GC and PolyKae/GC electrodes was evaluated in this study. For this luteolin and kaempferol were electrochemically polymerized on glassy carbon (GC) electrode surface in order to get polyluteolin and polykaempferol-modified glassy carbon electrodes (PolyLut/GC and PolyKae/GC, correspondingly). The formation of polyphenol layer on the GC electrode surface was evidenced by atomic force microscopy. Square wave voltammetry was found to be more sensitive in comparison with differential pulse voltammetry. It was determined that PolyLut/GC and PolyKae/GC electrodes offered great sensitivity towards Cu(II) ions with very low limit of detection, good reproducibility, sufficient stability and excellent selectivity of analytical signal. (C) 2011 Elsevier B.V. All rights reserved.
