Yazar "Çiftçi, Hakan" seçeneğine göre listele

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    Efficient removal of acidic dye using low-cost biocomposite beads
    (2013) Metin, Ayşegül Ülkü; Çiftçi, Hakan; Alver, Erol
    The objective of this study is to prepare and characterize chitosan/zeolite biocomposite beads and utilize them as adsorbent for removal of anionic dye, Acid Black 194 (AB194). Characterization studies of biocomposite beads were carried out by using Fourier transform infrared (FTIR), thermogravimetric analysis (TGA), and scanning electron microscopy energy dispersive X-ray spectroscopy (SEM-EDX). The ability of chitosan/zeolite biocomposite beads as an adsorbent for the removal AB194 from an aqueous solution has been investigated under various experimental conditions. Maximum adsorption capacity of biocomposite beads was calculated as 2140 mg/g. The increase in temperature resulted in a higher AB194 loading per unit weight of biocomposite beads. As an additional factor affecting the adsorption behavior of AB194, the effect of ionic strength was investigated, and the adsorption capacity of biocomposite beads significantly decreased. Four isotherm models were employed to elucidate the adsorption process. The most appropriate model for the equilibrium process was the Freundlich. The kinetic studies indicated that the adsorption of AB194 followed the pseudo-second-order kinetics. Thermodynamic calculations showed that the adsorption of reactive dye was a spontaneous and endothermic process. The obtained results indicate that chitosan/zeolite biocomposite beads as an adsorbent are promising for dye removal from wastewater. © 2013 American Chemical Society.
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    Electrochemical copper (II) sensor based on chitosan covered gold nanoparticles
    (Kluwer Academic Publishers, 2014) Çiftçi, Hakan; Tamer, Uğur; Metin, Ayşegül Ülkü; Alver, Erol; Kizir, Nevin
    This study outlines a new sensing platform based on glassy carbon electrodes modified by gold nanoparticles (AuNPs) for the determination of heavy metal. A glassy carbon electrode was modified by chitosan stabilized AuNPs. AuNPs were prepared by reducing gold salt with a polysaccharide chitosan. Here, chitosan acted as a reducing/stabilizing agent. The AuNPs were characterized with UV-Visible absorption spectroscopy, Fourier transform infrared spectroscopy, and transmission electron microscopy. Chitosan covered AuNPs were immobilized on the glassy carbon electrode for the determination of Cu (II) in aqueous solutions. The electrochemical determination of Cu (II) ions was performed using the differential pulse voltammetry technique. Some parameters for Cu (II) determination, such as pH, preconcentration time and electrolysis potential of Cu (II), were optimized. The detection limit was calculated as 5 × 10-9 mol L-1 by means of the 3:1 current-to-noise ratio. The interference of Cr(III), Fe(II), Ni(II), Pb(II), Mg(II), Zn(II), Ba(II) ions was investigated and showed a negligible effect on the electrode response. Recovery studies were carried out using tap water. © 2014 Springer Science+Business Media Dordrecht.
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    Fabrication and characterization of gold-nanoparticles/chitosan film: A scaffold for L929-fibroblasts
    (2013) Türk, Mustafa; Tamer, Uğur; Alver, Erol; Çiftçi, Hakan; Metin, Ayşegül Ülkü; Karahan, Siyami
    The objective of the present study was to fabricate a gold nanoparticle crosslinked chitosan (Ch/AuNPs) composite film simple and to evaluate its use as a carrier matrix for L929- fibroblasts. L929- fibroblasts were seeded either onto Ch or Ch/AuNPs scaffolds. The Ch/AuNPs scaffold exhibited a higher cell proliferation and growth rate. The cytotoxicity test determined trypan blue staining indicated that Ch scaffolds devoid of AuNPs expressed almost no toxicity while the Ch/AuNPs composite scaffolds expressed a very limited toxicity only at higher doses. The Ch/AuNPs scaffold promotes cell attachment, growth and proliferation with almost no cytotoxicity. © 2013 Informa Healthcare USA, Inc.
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    Non-enzymatic sensing of glucose using a glassy carbon electrode modified with gold nanoparticles coated with polyethyleneimine and 3-aminophenylboronic acid
    (Springer-Verlag Wien, 2016) Çiftçi, Hakan; Alver, Erol; Çelik, Filiz; Metin, Ayşegül Ülkü; Tamer, Uğur
    A non-enzymatic electrochemical method was developed for sensing glucose by using a glassy carbon electrode modified with 3-aminophenylboronic acid (APBA) immobilized on polyethyleneimine (PEI)-coated gold nanoparticles. The modified electrode was characterized by TEM, zeta potential measurements and UV-Vis spectroscopy. Its analytical performance was evaluated in pH 9 solution by potentiometry. The respective calibration plot, established at open circuit potential (vs. Ag/AgCl) covers the 0.5–50 mM glucose concentration range, which makes it suitable for blood glucose assays. The detection limit is 0.025 mM, and no interference is caused by ascorbic acid, dopamine, and uric acid. Effects of other carbohydrates such as fructose, galactose and saccharose were also investigated. The electrode was used to determine glucose in human serum samples and the results agreed well with those obtained with commercial amperometric enzymatic sensors. [Figure not available: see fulltext.] © 2016, Springer-Verlag Wien.
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    One step effective removal of Congo Red in chitosan nanoparticles by encapsulation
    (Elsevier B.V., 2017) Alver, Erol; Bulut, Mehmet; Metin, Ayşegül Ülkü; Çiftçi, Hakan
    Chitosan nanoparticles (CNPs) were prepared with ionotropic gelation between chitosan and tripolyphosphate for the removal of Congo Red. The production of chitosan nanoparticles and the dye removal process was carried out in one-step. The removal efficiency of Congo Red by encapsulation within chitosan from the aqueous solution and its storage stability are examined at different pH values. The influence of some parameters such as the initial dye concentration, pH value of the dye solution, electrolyte concentration, tripolyphosphate concentration, mixing time and speed on the encapsulation is examined. Congo Red removal efficiency and encapsulation capacity of chitosan nanoparticles were determined as above 98% and 5107 mg Congo Red/g chitosan, respectively. © 2016 Elsevier B.V.
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    Synthesis and Characterization of Chitosan/Polyvinylpyrrolidone/Zeolite Composite by Solution Blending Method
    (Springer New York LLC, 2014) Alver, Erol; Metin, Ayşegül Ülkü; Çiftçi, Hakan
    Polymer/clay composites have been studied for several decades; in the study, polymer/zeolite composite beads have been prepared by a simple solution blending method using chitosan, polyvinylpyrrolidone and zeolite particles as organic and inorganic components, respectively. Different techniques, such as SEM, FTIR spectroscopy, and thermogravimetry have been used to characterize the composite beads. Chitosan/polyvinylpyrrolidone/zeolite (CH/PVP/Z) beads are expected to have a potential as an adsorbent for wastewater treatment. To investigate its applicability, copper (II) was selected as a model compound. The results showed that the composite beads had effective loading capacity and it is a promising adsorbent for heavy metal removal. © 2014, Springer Science+Business Media New York.