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Öğe Degradation of contaminated industrial waste water using sol-gel derived Ru-doped TiO2 photocatalyticfilms [Sol-jel ile elde edilen Ru katki{dotless}li{dotless} TiO2 fotokatalitik filmler kullani{dotless}larak endüstriyel-kirli sularin ayriştirilmasi](2013) Erol M.; Sancakoglu O.; Mermer O.; Celik E.In this study, Ru-TiO2 films were deposited on glass substrates with a sol-gel route for degradation of contaminated industrial water. A solution with the Ru/Ti molar ratio of 0.05 was prepared using ruthenium and titanium based precursors. Solution characterizations were made using a turbidimeter and pH meter. The gel films, prepared by the sol-gel drop casting method, were dried at 300°C for 10 minutes and subsequently heat-treated at 500°C for 5 minutes in air. After that, the oxide thin films were annealed at 600°C for 60 minutes in air. In order to evaluate the phase structure, microstructure, optical, and photocatalytic properties of the coatings, they were investigated using XRD, SEM, and UV/Vis spectrophotometer, respectively. The obtained phase was mostly anatase TiO2. Photo-oxidation experiments were performed to obtain the photocatalytic activity of the films on impure water using an UV light source. The absorption spectrum of the water samples taken from Cigli Industrial Plant and Gediz River in Izmir/Turkey showed that they have absorbance bands in the range of 300 nm and 500 nm. The Ru doped TiO2 films exhibited highly photocatalytic activity to decompose organic species in contaminated waters. The degradation percentage ratios were calculated as 75% and 62% for two different industrial water samples.Öğe Electrochemical xanthine detection by enzymatic method based on Ag doped ZnO nanoparticles by using polypyrrole(Elsevier B.V., 2019) Sahyar B.Y.; Kaplan M.; Ozsoz M.; Celik E.; Otles S.A sensitive electrochemical detection of xanthine (X), which is an early biomarker of fish meat spoilage, was achieved by a novel biosensor developed via three main steps. The first step is the electropolymerization of a conducting polymer (pyrrole) onto the pencil graphite electrode (PGE). The second step is the entrapment of silver-doped zinc oxide nanoparticles (nano Ag–ZnO) onto PGE, which has already been doped with polypyrrole (PPy). The third step is the immobilization of the enzyme (xanthine oxidase) onto the modified electrode (nano Ag–ZnO/PPy/PGE) surface. The biosensor was characterized by scanning electron microscopy (SEM). The addition of Ag-doped ZnO nanoparticles into the conducting polymer structure played an important role in the performance of the biosensor by increasing the porous structure of the conducting polymer surface. The electrochemical behaviour of the biosensor was studied by electrochemical impedance spectroscopy (EIS) and chronoamperometry (CA). This enzyme biosensor showed the maximum response at pH 7.40 when +0.7 V was applied to reach 95% of steady-state current at ~3.2 s. The designed biosensor showed high selectivity with a sensitivity of 0.03 µA/mM and a low detection limit of 0.07 µM. © 2019 Elsevier B.V.Öğe A model for the calculation of mechanical properties of hydroxyapatite coatings on Ti6Al4V substrate using finite element methods(2011) Pasinli A.; Culha O.; Celik E.; Toparli M.The scope of this study is to find out yield curve on the coating-substrate system of hydroxyapatite (HA) by finite element modeling. With this regard, Hydroxyapatite (HA) coatings were successfully formed on Ti6Al4V substrates by using biomimetic technique. Experimental indentation tests were conducted on Dynamic Ultra-micro Hardness test machine. In finite element modeling (FEM), mechanical properties of coatings were determined by using ABAQUS software package. This numerical study was carried out using an axisymmetric FEM model. To calculate the mechanical properties of coating, the resulting load-unload test data of the samples obtained from the experimental indentation tests were analyzed and curvefitted in Kick's and Meyer's law for the loading and the unloading part of the loadunload curve respectively. Then, a set of analytical functions that take the pile-up and sink-in effects into account during instrumented sharp indentation were solved using numerical methods These analytical functions were defined within an identified representative plastic strain, ? r, for the Vickers indenter geometry as a strain level that allows for the description of the indentation loading response independent of strain hardening exponent, n. © Association for Scientific Research.Öğe A novel fluorescent nano-scale sensor for detection of trace amounts of Ca (II) ions(2014) Kacmaz S.; Ertekin K.; Oter O.; Mercan D.; Cetinkaya E.; Celik E.A photo-induced electron transfer (PET) based sensing approach for the direct determination of trace amounts of calcium ions is presented. The Ca 2+ selective fluoroionophore Bis, 2,2'-{1,2 phenylenebis [nitrilomethylylidene]} diphenol (DMK) was encapsulated in polymeric ethyl cellulose. The sensing membranes were fabricated in form of nanofibers, exploiting the prepared polymer. When embedded in nanomaterials, the DMK dye yielded strong absorbance, large Stoke's shift, high fluorescence quantum yield, and excellent short and long-term photostability. The sensing ability of the nanofibers was tested by steady state and time resolved fluorescence spectroscopy. To our knowledge, this is the first attempt using the DMK-doped electrospun nanofibrous materials for calcium sensing. The offered nanosensor displays a sensitive response with a detection limit of 0.016 nM for Ca 2+ ions over a wide concentration range, 1.0×10 -10-1.0×10-4 M, and exhibits high selectivity over Mg 2+ and other cations. Accuracy of the sensing system was proven by recovery tests. © 2013 Elsevier B.V.Öğe Oxygen sensing properties of embedded amphiphilic ruthenium(II) derivatives in presence of silver nanoparticles(American Scientific Publishers, 2015) Ay Z.; Ertekin K.; Celik E.; Varlikli C.; Sahin C.Most of the ruthenium dyes suffer from leaching from host matrices. In this work, alkyl branched Ru(II) derivatives were used along with silver nanoparticles (AgNPs) in two different silicon based matrices for oxygen sensing purposes. By this way, we securely entrapped the dye molecules without any leaching from the matrix. The sensing materials were fabricated in form of thin films and electrospun nanofibers. 1-butyl-3-methylimidazolium tetrafluoroborate ([BMI+][BF- 4 ]) and perfluoro compounds (PFCs) were exploited as additives to enhance the response to oxygen. O2 induced spectral changes at 630 nm were followed for both gas phase and dissolved oxygen as the analytical signal. The oxygen sensitivities of the probes were also tested by lifetime based and kinetic mode measurements. Utilization of the amphiphilic Ru dyes in silicon along with AgNPs in form of electrospun fibers resulted in many advantages such as enhanced long term stability, increased surface area, sensitivity and improvement in all sensor dynamics. Sensing characteristics of the offered design were also tested in presence of vapors of benzene, toluene, ethylbenzene, hexane and xylene. The offered composite can be employed for both, gas phase and dissolved O2 measurements even in refinery conditions. Copyright © 2015 American Scientific Publishers All rights reserved.Öğe Synthesis and characterization of Gd2O2SO4:Pr3+ scintillation material produced by Sol-Gel process for digital imaging system(Polish Academy of Sciences, 2017) Aritman I.; Yildirim S.; Kisa A.; Guleryuz L.F.; Yurddaskal M.; Dikici T.; Celik E.Scintillation materials are widely used in digital X-ray imaging applications, radiotherapy applications coupled with suitable photoreceptors. Gd2O2SO4 (GOS) scintillator doped with trivalent praseodymium (Pr3+) presented high X-ray absorption properties and good spectral compatibility which were utilized extensively for imaging system of X-ray microscopy, soft X-ray phosphor screen for water window. In this study, GOS:0.01Pr3+ scintillation material was synthesized by unique sol-gel process which was not previously applied and its characterization properties were investigated. Structure and luminescence properties of GOS:Pr3+ were optimized by utilizing X-ray diffraction, X-ray photoelectron spectroscopy, scanning electron microscopy, and luminescence spectroscopy.Öğe An ultra sensitive fluorescent nanosensor for detection of ionic copper(Elsevier, 2015) Kacmaz S.; Ertekin K.; Mercan D.; Oter O.; Cetinkaya E.; Celik E.A stable and ultra sensitive nano-scale fluorescent chemo-sensor for trace amounts of Cu2+ was proposed. The Cu2+ selective fluoroionophore 2-{[(2-aminophenyl)imino]methyl}-4,6-di-tert-butylphenol (DMK-7) was encapsulated in polymeric ethyl cellulose. The sensing membranes were fabricated in form of nanofibers and thin films. When embedded in polymers, the exploited DMK-7 dye exhibited enhanced photophysical characteristics in absorbance, Stoke's shift, fluorescence quantum yield, and short and long-term photostability with respect to the solution phase. Sensing abilities of the nanofibers and thin films were tested by steady state and time resolved fluorescence spectroscopy. To our knowledge, this is the first attempt using the DMK-7-doped electrospun nanofibrous materials for copper sensing. The offered sensor displayed a sensitive response with a detection limit of 3.3 × 10-13 M for Cu2+ ions over a wide concentration range of 5.0 × 10-12-5.0 × 10-5. Additionally, exhibited high selectivity over convenient cations; Na+, K +, Ca2+, Mg2+, NH4+ and Ag+, Al3+, Ba2+, Co2+, Cr 3+, Fe3+, Fe2+, Hg2+, Li +, Mn2+, Ni2+, Pb2+, Sn2+ and Zn2+. © 2014 Elsevier B.V. All rights reserved.
