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    Biosorption of reactive dyes on Scenedesmus obliquus
    (Elsevier Science Bv, 2005) Tan, S.; Katircioğlu, Hikmet; Öktem, Zeki; Ergene, Aysun
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    Controlled cationic polymerization of furfuryl alcohol
    (Pergamon-Elsevier Science Ltd, 2013) Ünver, Halil; Öktem, Zeki
    CuCl/N,N,N',N '',N ''-pentamethyldiethylenetriamine catalyst system was used successfully in the controlled cationic polymerization of furfuryl alcohol initiated with benzyl bromide in acetonitrile. Polymerizations were carried out at 110 degrees C open to air. The effect of reaction time, amount of initiator and solvent on the rate of polymerization was studied. The linear kinetic plot of In([M](o)/[M]) versus polymerization time, linear dependence of the molecular weight on the monomer conversion and low polydispersity of the polymers (1.07-1.50) showed the characteristics of the controlled polymerization. Soluble polymers with M-n up to 6.6 kg/mol were obtained. The structural analysis of the polymer was carried out by H-1 NMR, C-13 NMR, FTIR and UV-VIS spectroscopies. Formation of carbonyl groups and -CH2-O-CH2- bridges on poly(furfuryl alcohol) chains were observed. Thermal properties of the polymer were studied by DSC and TGA analyses. (C) 2013 Elsevier Ltd. All rights reserved.
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    Furfuril alkol ve furfurilaminin atom transfer radikal polimerleşmesi
    (Kırıkkale, 2012) Öktem, Zeki; Ünver, Halil
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    Preconcentration and electroanalysis of copper at glassy carbon electrode modified with poly(2-aminothiazole)
    (Gazi Univ, 2011) Çiftçi, Hakan; Testereci, H. Nur; Öktem, Zeki
    Conducting poly(2-aminothiazole), PAT, was synthesized in acetonitrile with tetrabutylammonium tetrafluoroborate, TBAFB, as supporting electrolyte via constant potential electrolysis, CPE. Glassy carbon, GC, electrode was modified by immersing the electrode in a DMSO solution of PAT. Preconcentration of copper on polymer matrix was carried out at -0.7 V. The effects of preconcentration time and pH and Cu(II) concentration of the preconcentration solution on the stripping peak current of copper were studied.
  • [ X ]
    Öğe
    Voltammetric determination of Hg(II) at poly(2-aminothiazole) modified platinum electrode
    (Parlar Scientific Publications (P S P), 2011) Çiftçi, Hakan; Öktem, Zeki
    Conducting poly(2-aminothiazole) (PAT) film was electrodeposited on platinum disc electrode surface by cyclic voltammetry of 2-aminothiazole (AT) for stripping voltammetric determination of Hg(II). Hg(II) was pre-concentrated on to polymer matrix by adsorption upon dipping the modified electrode into Hg(II) solution. The effect of electrolysis time, number of electropolymerization cycles, pH, preconcentration time and Hg(II) concentration on the determination of Hg(II) were studied. A linear relation between the peak current and Hg(II) concentration was obtained in the range of 0.1-1.1 mg L-1. The relative standard deviation was calculated as 1.37% at 0.5 mg L-1 Hg(II) (n=6). The detection limit was estimated as 0.025 mg L-1 by means of 3:1 current-to-noise ratio. The interferences of Ni(II), Cu(II), Pb(II), Zn(II), Cd(II) and Fe(III) were investigated in the determination of Hg(II). The optimized method was successfully applied to the determination of Hg(II) in the River Kizilirmak samples by means of standard addition method.