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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 Covalent grafting of three flavonoids onto the glassy carbon electrode surface by cyclic voltammetry(WALTER DE GRUYTER GMBH, 2011) Mulazimoglu, Ibrahim Ender; Ustundag, Zafer; Ozkan, Erdal; Solak, Ali OsmanElectrochemical oxidation of quercetin (QR), 3-hydroxyfl avone (3HF), and baicalein (BN) and their grafting onto the glassy carbon (GC) electrode have been studied using the cyclic voltammetric (CV) technique. Electrochemical studies were performed within a one-compartment three-electrode cell at room temperature. The modification was carried out only in nonaqueous media, while the electrochemical characterization was done in both aqueous and nonaqueous media. In the nonaqueous experiments, 0.1 m tetrabutylammonium tetrafluoroborate in acetonitrile was used, whereas in the aqueous experiments, Britton-Robinson buffer solutions (pH = 2) and 0.1 m KCl solutions were. Surface modifi cations were performed by CV for all compounds. The presence of QR, 3HF, and BN at the GC electrode surface was characterized by CV, electrochemical impedance spectroscopy, contact angle measurement, ellipsometry, and atomic force microscopy.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 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 Surface modification and characterization of phenanthroline nanofilms on carbon substrate(WILEY, 2011) Oztekin, Yasemin; Yazicigil, Zafer; Solak, Ali Osman; Ustundag, Zafer; Kilic, Zeynel; Bilge, SelenModification of glassy carbon (GC) surfaces with phenanthroline derivatives (PDs) such as 5-amino-1,10-phenanthroline (5AP) and 5,6-diamino-1,10-phenanthroline (56DAP) is described in this study. Surface modification experiments were performed by cyclic voltammetry (CV) scanning from +1.2 to +2.7 V at scan rate of 100 mV/s applying 30 potential scans in acetonitrile (CH3CN) containing 1 mMPDs and 100 mM tetrabutylammoniumtetrafluoroborate (TBATFB). The presence of PDs on GC electrode was confirmed using CV, electrochemical impedance spectroscopy (EIS), contact angle measurements and ellipsometry and comparing with the results of bare GC electrode. A mechanism was proposed for the electrochemical modification of the GC electrode surface with PDs. The structure of the 5AP and 56DAP films was also discussed in the light of electrochemical and spectroscopic data. The complex-forming ability of the modified surfaces against metal cations was investigated by square-wave voltammetry (SWV). It was shown that surfaces having 1,10-phenanthroline ligands with different functional groups were quite useful for the determination of transition metal ions. Copyright (C) 2010 John Wiley & Sons, Ltd.Öğe Synthesis of some azacrown derivatives and fabrication of their nanofilms on the glassy carbon surface(SPRINGER, 2012) Deveci, Pervin; Taner, Bilge; Ustundag, Zafer; Kilic, Zeynel; Solak, Ali Osman; Ozcan, EmineThe modification of N-phenyl-aza-15-crown-5 (PA15C5) and N-(4-aminophenyl)-aza-15-crown-5 (4APA15C5) on glassy carbon (GC) electrode was performed by the electrochemical oxidation of the corresponding azacrown derivatives in anhydrous acetonitrile media. The electrochemical behavior of the resulting modified GC electrode was investigated in the presence of electroactive redox probes and these results, together with the X-ray photoelectron spectroscopy (XPS) and reflection-absorption infrared spectroscopy were used to confirm the attachment of these molecules onto the GC surface. The ellipsometric thicknesses of PA15C5 and 4APA15C5 films at the GC surface was obtained around 9.28 +/- 0.40 and 10.50 +/- 1.10 nm, respectively. Azacrown modified nanoscale surfaces serve as alkali metal sensor specific for their cavity in the crown ring.
