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Öğe Adsorption of Cu(II) From Aqueous Solution by Using Modified Fe3O4 Magnetic Nanoparticles(Elsevier, 2010) Özmen, Mustafa; Can, Keziban; Arslan, Gülsin; Tor, Ali; Çengeloğlu, Yunus; Ersöz, MustafaIn this study, surface modification of Fe3O4 nanoparticles (Fe3O4-NPs) was carried out with 3-aminopropyltriethoxysilane (APTES) and glutaraldehyde (GA). The obtained modified-NPs (GA-APTES-NPs) were evaluated for Cu(II) removal from water by adsorption. First, Fe3O4-NPs were synthesized by co-precipitation of Fe2+ and Fe3+ with Fe2+/Fe3+ in a ratio of 1.75 in an ammonia solution, then surface of Fe3O4-NPs was modified with APTES and GA. The morphology and properties of the NPs were examined by Transmission Electron Microscopy (TEM), Fourier Transform Infrared Spectroscopy (FT-IR), Thermal Gravimetric Analysis (TGA) and magnetization measurement. The batch experiments showed that modified-NPs can be effectively used to remove Cu(II) from water. Adsorption equilibrium was achieved in 15 min. The adsorption of Cu(II) by GA-APTES-NPs strongly depends on the pH of the solution. Maximum removal of Cu(II) was obtained at pH between 4.0 and 5.3. The isotherm analysis indicated that the sorption data can be represented by both Langmuir and Freundlich isotherm models. The regeneration studies also showed that GA-APTES-NPs could be re-used for the adsorption of Cu(II) from aqueous solutions over three cycles without change in the sorption capacity and magnetization properties.Öğe Fabrication of Octyltriethoxysilane Langmuir-Blodgett Thin Film(Natl Inst Optoelectronics, 2010) Can, Keziban; Özmen, Mustafa; Gürfidan, L.; Gübbük, İlkay Hilal; Kaymak, E.; Ersöz, Mustafa; Özbek, Zikriye; Çapan, R.In the present work the monolayer properties at the air-water interface of Octyltriethoxysilane (C8TES) molecules are investigated using Langmuir isotherm graphs. Uniform and high quality Langmuir-Blodgett films of these molecules are prepared and characterized by UV-visible, atomic force microscopy and quartz crystal microbalance measurements to determine the deposition quality of these films. High transfer ratio of about 0.99 at a deposition pressure of 11 mN/m was obtained. The contact angle of water was 93.17 degrees with a surface free energy of 23.8 mN/m. The use of soluble triethoxy-based silane coupling agents under anhydrous conditions is shown to produce surfaces with a minimal number of surface defects. C8TES material has been demonstrated to produce well organised LB films and is shown to be a good candidate for application in the field of biosensors.Öğe Immobilization of albumin on aminosilane modified superparamagnetic magnetite nanoparticles and its characterization(ELSEVIER SCIENCE BV, 2009) Can, Keziban; Ozmen, Mustafa; Ersoz, MustafaMagnetite nanoparticles (NPs) were synthesized by co-precipitating Fe2+ and Fe3+ in an ammonia solution. Magnetite NPs coated with 3-aminopropyltriethoxysilane (APTES) were prepared by silanization reaction. After activated with glutaraldehyde (CA), human serum albumin was covalently immobilized on these magnetic NPs. The influence of three different buffer solutions on covalent immobilization was studied. phosphate buffer saline solution (PBS) was shown the highest binding ability for immobilization process compared to other buffer solutions. The morphology and properties of these magnetic NPs were examined by transmission electron eicroscopy (TEM), Fourier transform infrared spectroscopy (FTIR), thermal gravimetric analysis (TGA) and magnetization measurement. (C) 2009 Elsevier B.V. All rights reserved.Öğe Immobilization of albumin on indium-tin oxide (ITO) surface via isocyanate linkage(ELSEVIER SCIENCE SA, 2009) Ozmen, Mustafa; Can, Keziban; Ersoz, MustafaIndium-tin oxide (ITO) surfaces have become a very important material for use as a conducting substrate, recently. Immobilization of biological molecule onto the ITO is a fundamental step in the development of biosensors. In this paper, attachment of albumin was carried out using ITO as a support. Albumin was covalently immobilized onto self-assembled monolayer (SAM) of (3-isocyanatopropyl) triethoxysilane (IPTES) on ITO surface. Isocyanato-functionalized organic film was prepared by self-assembling on active ITO surface. After that, human serum albumin (HAS) which was prepared in Phosphate-Buffered Saline Solution (PBS: pH 7.4, 0.1 M), was covalently immobilized on IPTES modified ITO surface. The study here can help us understand the influence of monolayer and electrochemical behavior on ITO surface. Characterization of stepwise changes of active ITO, IPTES/ITO and albumin/IPTES/ITO surfaces were carried out using contact angle (CA) measurements, fluorescence microscopy, atomic force microscopy (AFM), electrochemical impedance spectroscopy (EIS) and cyclic voltammetry (CV), respectively. (C) 2009 Elsevier B.V. All rights reservedÖğe Immobilization of Candida rugosa lipase on glass beads for enantioselective hydrolysis of racemic Naproxen methyl ester(ELSEVIER SCI LTD, 2011) Yilmaz, Elif; Can, Keziban; Sezgin, Mehmet; Yilmaz, MustafaCandida rugosa lipase (CRL) was immobilized on glutaraldehyde-activated aminopropyl glass beads by using covalent binding method or sal-gel encapsulation procedure and improved considerably by fluoride-catalyzed hydrolysis of mixtures of RSi(OCH3)(3) and Si(OCH3)(4). The catalytic properties of the immobilized lipases were evaluated into model reactions, i.e. the hydrolysis of p-nitrophenylpalmitate (p-NPP). It has been observed that the percent activity yield of the encapsulated lipase was 166.9, which is 5.5 times higher than that of the covalently immobilized lipase. The enantioselective hydrolysis of racemic Naproxen methyl ester by immobilized lipase was studied in aqueous buffer solution/isooctane reaction system and it was noticed that particularly, the glass beads based encapsulated lipases had higher conversion and enantioselectivity compared to covalently immobilized lipase. In short, the study confirms an excellent enantioselectivity (E > 400) for the encapsulated lipase with an ee value of 98% for S-Naproxen. (C) 2010 Elsevier Ltd. All rights reserved.Öğe Katı yüzeylere farklı yapıda kendiliğinden toplanan tekli tabakaların (SAMs) oluşturulması ve karakterizasyonu(Selçuk Üniversitesi Fen Bilimleri Enstitüsü, 2009) Can, Keziban; Ersöz, MustafaBu çalışmada, son zamanlarda özellikle nanoteknolojik çalışmalarda kullanımı nedeni ile cam yüzeyi ve indiyum kalay oksit kaplı cam yüzeylere kendiliğinden toplanan tekli tabakaların oluşturulması ve karakterizasyonu incelenmiştir. Bu işlem için öncelikle yüzeyler, çeşitli çözelti ve organik çözücülerle aktif hale getirmek için muamele edilmişlerdir. Daha sonra aktifleştirilmiş yüzeylere (3-aminopropil)-trietoksisilan(APTES), (3-izosiyanatopropil)trietoksisilan(IPTES), Oktadesiltrimetoksisilan(OTMS), Oktiltrietoksisilan(OTES), bileşikleri kullanılarak kendiliğinden toplanma prosesine göre silanlama işlemi uygulanmıştır. Yüzeylerin hidrofilik ve hidrofobik özellikleri incelenmiştir. Bu aşamadan sonra biyolojik bileşik olan Albuminin IPTES modifiyeli yüzeye bağlanması amaçlanmıştır. Her bir adımdaki reaksiyonlar fluoresans mikroskobu, temas açısı ölçümü, atomik kuvvet mikroskobu (AFM), elektokimyasal impedans spektroskopisi (EIS) ve dönüşümlü voltametre (CV) ile karakterize edilmiştir. Böylece cam yüzeyi ve indiyum kalay oksit cam yüzeyi arasındaki farklılıklar belirtilmiştir.Öğe Surface modification of glass beads with glutaraldehyde: Characterization and their adsorption property for metal ions(ELSEVIER, 2009) Ozmen, Mustafa; Can, Keziban; Akin, Ilker; Arslan, Gulsin; Tor, Ali; Cengeloglu, Yunus; Ersoz, MustafaIn this study, a new material that adsorbs the metal ions was prepared by modification of the glass beads surfaces with glutaraldehyde. First, the glass beads were etched with 4 M NaOH solution. Then, they were reacted with 3-aminopropyl-triethoxysilane (APTES). Finally, silanized glass beads were treated with 25% of glutaraldehyde solution. The characterization studies by using Fourier Transform Infrared Spectroscopy (FT-IR),Thermal Gravimetric Analysis (TGA), elemental analysis and Scanning Electron Microscopy (SEM) indicated that modification of the glass bead surfaces was successfully performed. The adsorption studies exhibited that the modified glass beads could be efficiently used for the removal of the metal cations and anion (chromate ion) from aqueous solutions via chelation and ion-exchange mechanisms. For both Pb(II) and Cr(VI), selected as model ions, the adsorption equilibrium was achieved in 60 min and adsorption of both ions followed the second-order kinetic model. It was found that the sorption data was better represented by the Freundlich isotherm in comparison to the Langmuir and Redlich-Peterson isotherm models. The maximum adsorption capacities for Pb(II) and Cr(VI) were 9.947 and 11.571 mg/g, respectively. The regeneration studies also showed that modified glass beads could be re-used for the adsorption of Pb(II) and Cr(VI) from aqueous solutions over three cycles. (C) 2009 Elsevier B.V. All rights reserved.
