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Öğe Amperometric Simultaneous Measurement of Copper and Cobalt Ions with Polythiophene Incorporating Pendant Terpyridine Groups(Taylor & Francis Inc, 2014) Savan, Ebru Kuyumcu; Koytepe, Suleyman; Pasahan, Aziz; Erdogdu, Gamze; Seckin, TurgayTerpyridine containing thiophene monomer was synthesized. Electrochemical behavior of the monomer was studied by cyclic voltammetry. This monomer was polymerized via electrochemical methods and the resultant polymer was characterized. The stepwise fabrication process of the polymeric film electrode and its electrochemical sensing performance towards simultaneously Co and Cu ions were evaluated. The sensing parameters of the polymer electrode were investigated in detail, and the determination conditions were optimized. Under the optimal conditions, sensor response peak is linear to the Co ion concentration in the range of 1.0-50.0 mu M and the Cu ion concentration in the range of 1.0-20.0 mu M. Detection limit of terpyridine-based polythiophene film electrode for Co and Cu is respectively 100 nM and 0.05 nM.Öğe Development of gallic acid sensors based on polyimide-modified platinum electrode(Taylor & Francis Inc, 2019) Pasahan, Aziz; Ayhan, Nurcan; Ozcan, Imren; Duran, Serap Titretir; Koytepe, SuleymanA series aromatic polyimide (PI) membranes in the form of permselective films was synthesised from different dianhydrides with two diamine monomers for gallic acid (GA) measurement. The obtained PI films were examined by Spectroscopic techniques, Scanning Electron Microscopy (SEM) and thermal analysis techniques and then used to fabricate the selective films on the modified electrode. Because of their excellent film properties, as the permselective polymeric membranes were used for determination of GA in the presence of various interferences and real sample. The PI-1-modified Pt electrode showed a very high R-value (0.9935) and reproducibility for GA determination, as well as high selectivity. [GRAPHICS]Öğe Electropolymerized Polytyramine Film for the Selective Determination of Uric Acid(Taylor & Francis Inc, 2012) Kursun, Sezen; Pasahan, Aziz; Ekinci, Bilge Zabci; Ekinci, ErgunElectropolymerized polytyramine film was proposed for determination of uric acid in the presence of ascorbic acid. The influence of electropolymerization conditions on performance of the polytyramine film was examined to obtain the optimal experimental parameters. The voltammetric results demonstrated that polytyramine film obtained at the optimized conditions allowed penetration of large amounts of uric acid while blocking the permeation of electroactive (ascorbic acid, cysteine and oxalic acid) and non-electroactive interferents (lactose, sucrose and urea) through film in PBS. Therefore, it has been claimed that the polymeric film could be used as uric acid-selective membrane over a broad range of interference.Öğe Fructose-Based Polyurethane Membranes: Synthesis, Characterization, and Their Use as Voltammetric pH Electrode(Taylor & Francis As, 2015) Gungor, Oznur; Pasahan, Aziz; Cengiz, Mahmut Alper; Koytepe, Suleyman; Seckin, TurgayIn this study, polyurethane films prepared from the 4,4-diphenylmethane diisocyanate (MDI), ethylene glycol, and different ratio fructose were used to prepare a novel amperometric pH electrode. Fructose-based films were characterized by FT-IR, DSC, DTA, and TGA. Prepared polyurethanes exhibited suitable T-g(degrees C), good thermal stability and good adhesive properties. The incorporation of saccharides into the PU structure results in a higher crosslinking density and a higher content of hard segments. Furthermore, the behavior of films prepared from polyurethane solutions containing 1%, 3%, 5%, and 10% fructose toward pH changes were examined by normal pulse voltammograms technique and diferantial pulse voltammetry. [GRAPHICS] .Öğe Maltose-Containing Polyurethane Films: Synthesis, Characterization, and Their Use for Determination of Dopamine in the Presence of the Electroactive and Nonelectroactive Interferents(Taylor & Francis As, 2013) Pasahan, Aziz; Koeytepe, Sueleyman; Cengiz, M. Alper; Seckin, TurgayA series of polyurethanes were prepared from the maltose-ethylene glycol-diphenylmethane diisocyanate and used to construct a novel polyurethane electrode for the detection of dopamine. The polyurethanes were characterized by FT-IR, differential scanning calorimetry, and thermogravimetric analysis. The intrinsic viscosity and adhesive properties were also evaluated. Selectivity behaviour of films prepared from polyurethane solutions containing 1%, 3%, 5%, and 10% maltose to electroactive and nonelectroactive substances was examined by DPV. The results demonstrated that polymer electrode by 2 mu L polyurethane solutions containing 3% maltose was allowed penetration of dopamine while blocking the permeation of ascorbic acid and uric acid through film.Öğe A novel electrochemical biosensor based on polyimide- boron nitride composite membranes(Taylor & Francis As, 2017) Aksoy, Busra; Pasahan, Aziz; Gungor, Oznur; Koytepe, Suleyman; Seckin, TurgayPolyimide (PI) and polyimide-boron nitride (PI-BN) composites as dopamine-selective membrane were synthesized. The structures of the monomer, pure PI, and PI-BN composites were characterized by FT-IR, SEM, and thermal analysis techniques. Experiment results showed that introduction of BN particles increased porosity, selectivity and improved heat-resistance of polyimide matrix. Selectivity of PI-BN composite membranes toward dopamine and interferences was examined by DPV technique. Electrochemical measurement results illustrated that polyimide membrane containing 5% BN possessed wide linear ranges, excellent sensitivity, selectivity, reversibility, and low detection limits (4 X 10(-8) M). The polyimide membrane was very high R value (0.9904). [GRAPHICS] .Öğe Poly (3-aminophenol) Film as a Uric Acid-Selective Electrode(Taylor & Francis As, 2011) Kursun, Sezen; Pasahan, Aziz; Ekinci, Bilge Z.; Ekinci, ErgunIn order to prepare uric acid-selective polymeric membrane in the presence of electroactive (ascorbic acid, cysteine, oxalic acid) and nonelectroactive (lactose, sucrose and urea) substances, poly (3-aminophenol) films were prepared by means of electropolymerization on Pt electrodes. By systematically investigating the influence of polymerization conditions on sensor performance of the poly (3-aminophenol) film, the optimal parameters were determined. The voltammetric results showed that polymeric films obtained at the optimized conditions were allowed penetration of large amounts of uric acid (UA) while rejecting ascorbic acid, cysteine and oxalic acid in PBS. Therefore, it has been claimed that the polymeric films could be used as uric acid-selective membrane.Öğe Poly[tris((p-aminophenoxy)phosphineoxide)-3,3?,4,4?-benzophenonetetracarboxylicdiimide] as a New Polymeric Membrane for the Fabrication of an Amperometric Glucose Sensor(Taylor & Francis As, 2011) Pasahan, Aziz; Koytepe, Suleyman; Ekinci, ErgunPoly[tris((p-aminophenoxy)phosphineoxide)-3,3',4,4'-benzophenonetetracarboxylicdiimide] (PAB) was used as an immobilized enzyme membrane for the fabrication of an amperometric glucose sensor. Enzyme immobilization was performed by two different methods and structural morphology of immobilized enzyme membrane was studied by SEM. The amperometric response of the sensor to hydrogen peroxide, formed as the product of the enzymatic reaction, was measured at a potential of 0.7 V in phosphate buffer solution by means of the TB technique. The influence of preparation conditions (polyimide film thickness, enzyme amount) on electrode performance was examined to obtain the optimal experimental parameters. Sensor characteristics (pH, response time, selectivity, stability) of the PAB/GOx/Pt electrode prepared under optimal conditions has been investigated. Results showed that this sensor exhibited a linear range up to 6 mM and a response time of about 60 s. with good stability. When glucose was injected into the PBS solution in the presence of fouling substances (lactose, sucrose, and urea), excellent amperometric responses were observed. Also, it was seen that the PAB/GOx-Pt electrode blocked the signal current of electroactive oxalic acid.Öğe Preparation and Properties of Amperometric Uric Acid Sensor Based on Poly(2-aminophenol)(Wiley, 2011) Kursun, Sezen; Ekinci, Bilge Z.; Pasahan, Aziz; Ekinci, ErgunPoly(2-aminophenol) films were electrochemically prepared on Pt electrodes at a constant potential from a deoxygenated aqueous solution of monomer dissolved in 0.1 M KCl. The uric acid selectivity of polymeric electrodes prepared at the different thicknesses was examined in the presence of ascorbic acid. The results showed that the polymeric film allows penetration of large amounts of uric acid while blocking the electrochemical activity of ascorbic acid in the potential region examined when compared with that on the bare Pt electrode. The regular and repetitive responses for uric acid were obtained even in the presence of the interfering substances such as ascorbic acid, cysteine, oxalic acid, lactose, sucrose, and urea. Moreover, the stability and the reversibility of the polymeric sensor were satisfactory. Therefore, it has been claimed that the polymeric electrode could be used as uric acid-selective membrane in the presence of the mentioned interfering species. (C) 2010 Wiley Periodicals, Inc. J Appl Polym Sci 120: 406-410, 2011Öğe Preparation and properties of selective polyurethane films and their use for the development of biomedical dopamine sensor(Taylor & Francis As, 2016) Savan, Ebru Kuyumcu; Pasahan, Aziz; Aksoy, Busra; Gungor, Oznur; Koytepe, Suleyman; Seckin, TurgayPolyurethane films were synthesized by 3,4-divanillyltetrahydrofuran and different diisocyanates. These prepared polyurethanes were characterized by FT-IR, DSC, DTA, and TGA techniques. For the amperometric applications, synthesized polyurethanes exhibited suitable T-g (degrees C), good thermal stability and good adhesive properties. In addition, because of their interesting film properties, attempts were made to prepare dopamine-sensing electrode. For this reason, selectivity of film-coated electrodes obtained from the chemically prepared polyurethanes toward electroactive and nonelectroactive species were examined by means of DPV technique. From the electrochemical results obtained, it has been demonstrated that the PU-1-coated electrode can be used for the development of biomedical sensor.Öğe Preparation of triaminotriazine-based polyimide-modified electrodes and their use for selective detection of catechin in green tea samples(Springer, 2020) Duran, Serap Titretir; Ayhan, Nurcan; Aksoy, Busra; Koytepe, Suleyman; Pasahan, AzizAn effective electrochemical sensor was developed from triaminotriazine-based polyimide (PI) films as selective membrane for the detection of catechin (CT). Firstly, triaminotriazine-based PI films were synthesized from 2,4,6-triamino-1,3,5-triazine (TAT) and pyromellitic dianhydride by thermal imidization method with different monomer ratios. Structural and morphological of synthesized PI films were characterized by Fourier transform infrared spectroscopy, scanning electron microscopy, and atomic force microscopy. Prepared polyimide films were used as membrane for the preparation of the modified electrodes. Catechin (CT) selectivity behavior of polyimide-modified Pt electrodes was investigated by means of differential pulse voltammetry (DPV). DPV voltammograms showed that peak currents of the modified electrode increased proportionally with increase in CT concentration. TAT-PI-1/1 sensor showed high selectivity, a high regression coefficient (R value = 0.9982 ), good repeatability (RSD of 2.15%), and limit of detection 0.0152 mM for catechin determination in the presence of multiple interferent species (1 mM coumaric acid, ascorbic acid, gallic acid, lactose, sucrose, fructose, maltose and glucose). Moreover, the TAT-PI-1/1 sensor was employed to determine CT in real sample.Öğe Preparation, characterization, and biocompatibility of chondroitin sulfate-based sol-gel coatings and investigation of their effects on osseointegration improvement(Taylor & Francis As, 2023) Pasahan, Aziz; Sevimli, Resit; Kivilcim, Nilufer; Acari, Idil Karaca; Erenler, A. Sebnem; Sezer, Selda; Durmat, H. TurgutIn this work, implants with enhanced antibacterial and surface properties besides mechanical, biological, and chemical properties were prepared with the replacement of traditional titanium and titanium alloys in the field of biomedical materials. Titanium substrates were coated with chondroitin sulfate (CS) containing (3-glycidoxypropyl)trimethoxysilane (GLYMO) and tetraethoxysilane (TEOS) based thin film using sol-gel technology. Chondroitin sulfate is a preferred material due to its characteristics antioxidative and osseointegresion properties besides its collagen-forming properties. Coated implants were morphologically elucidated with atomic force microscopy (AFM), and scanning electron microscopy (SEM). The structure of the chondroitin sulfate-containing films was investigated with Fourier Transform Infrared Spectroscopy (FTIR) and Energy Dispersive X-Ray Analysis (EDX) techniques. The obtained CS-based sol-gel surface coatings are thermally stable up to similar to 200 degrees C according to TGA and DTA analysis results. The biological and antibacterial properties of the coatings were also determined. The biocompatibility and osseointegration properties of the coatings developed within the scope of the study were, determined by in vivo studies on rats. According to biocompatibility results of CS/Sol-Gel coated surfaces, Cell viability (%) rates of CS-based coatings showed between 89 and 66%. According to the experimental data, it has been claimed that implants improved with antibacterial, stable, homogeneous, and biocompatible coatings can be used as a new alternative product for dental and orthopedic applications.Öğe Öğe Synthesis and characterization of polyurethanes containing glucose for selective determination of epinephrine in the presence of a high concentration of ascorbic acid(Wiley-Blackwell, 2013) Pasahan, Aziz; Koytepe, Suleyman; Cengiz, Mahmut Alper; Seckin, TurgayPolyurethane (PU) films were prepared from glucose, ethylene glycol and diphenylmethane diisocyanate and used to construct a novel polymer electrode for the detection of epinephrine (EP) in the presence of a high concentration of ascorbic acid (AA). The NCO:OH molar ratio was kept constant at 1 and the saccharide content was varied. The PUs were characterized using Fourier transform infrared spectroscopy, differential scanning calorimetry and differential thermal and thermogravimetric analyses, with intrinsic viscosity and adhesive properties also being evaluated. The PUs exhibited high glass transition temperature, good thermal stability and good adhesive properties. The incorporation of saccharides into the PU structure resulted in a higher crosslinking density and a higher content of hard segments. Medium- to high-molecular-weight polymers were obtained, with inherent viscosities near or higher than 0.982.14 dL g-1. The solubility of the PUs was much better than that of aromatic PUs. The modified polymer electrodes were then used to determine EP in the presence of a high concentration of AA using differential pulse voltammetry. From the amperometric results for the PU electrode, it is concluded that a PU film containing 5 wt% glucose can be used as a membrane for EP detection in the presence of a large concentration of AA, because of its strong adherence to the electrode surface, easy preparation, chemical stability, selectivity and very high statistical confidence (R = 0.9994). (C) 2012 Society of Chemical IndustryÖğe Synthesis of sterically hindered N-benzyladamantyl substituted benzimidazol-2-ylidene palladium complexes and investigation of their catalytic activity in aqueous medium(Pergamon-Elsevier Science Ltd, 2017) Dehimat, Zineb Imene; Pasahan, Aziz; Tebbani, Dahmane; Yasar, Sedat; Ozdemir, IsmailNHC-Pd-PEPPSI complexes with bulky benzyladamantyl substituted N-heterocyclic carbenes (NHC) were synthesized and characterized by NMR, HRMS, and micro analysis. These complexes were then used for Suzuki-Miyaura coupling reactions between aryl bromides and phenylboronic acid. With low catalyst, loading, all synthesized complexes rapidly catalyzed the Suzuki-Miyaura cross-coupling reaction in iPrOH/water (1:3 v/v) at room temperature in air. All palladium compounds were stable and had high catalytic activity for the Suzuki-Miyaura coupling reaction. (C) 2017 Elsevier Ltd. All rights reserved.Öğe Synthesis, Characterization of a New Organosoluble Polyimide and Its Application in Development of Glucose Biosensor(Taylor & Francis Inc, 2011) Pasahan, Aziz; Koytepe, Suleyman; Ekinci, ErgunA new aromatic organosoluble polyimide was synthesized from the 4,4'-Diaminodiphenileethane with 3,3',4,4'-benzophenonetetracarboxylic dianhydride (BTDA) via a conventional two-stage process. This polymer showed good solubilities in N-methyl-2-pyrrolidone and m-cresol. The polyimide was characterized by FT-IR, GPC, TGA, DSC and DTA, with intrinsic viscosity and adhesive properties also being evaluated. Then, glucose oxidase (GOD) enzyme was immobilized into aromatic organosoluble polyimide by two different methods. It was demonstrated that the poly[4,4'-Diamina very promising substrate for the immobilization and stabilization of enzymes and the development of highly stable biosensors.Öğe Synthesis, Characterization of Guar-Containing Polyurethane Films and their Non-enzymatic Caffeic Acid Sensor Applications(Taylor & Francis Inc, 2017) Duran, Serap Titretir; Pasahan, Aziz; Ayhan, Nurcan; Gungor, Oznur; Cengiz, Mahmut Alper; Koytepe, SuleymanStable voltammetric sensors were fabricated by dropping the guar-containing polyurethane films on a platinum electrode for the non-enzymatic determination of caffeic acid. The voltammetric responses of PU-G-1% toward caffeic acid have a linear concentration range from 1 to 15mM with a correlation coefficient of 0.9938. The detection limit of PU-G-1% electrode was approximately 0.25mM. PU-G-1% sensor showed the good sensitivity, selectivity, high R-value, low detection limit, and high reproducibility toward caffeic acid. Therefore, it is claimed that the polyurethane film containing 1% guar can be used as an excellent selective membrane for caffeic acid detection in the presence of interferent molecules. [GRAPHICS] .Öğe Synthesis, characterization of naphthalene-based polyimides, and their use as immobilized enzyme membrane(Wiley, 2011) Pasahan, Aziz; Koytepe, Suleyman; Ekinci, ErgunA new monomer, 1,5-bis(p-dimethylaminophenylimino)naphthalene, was prepared through Schiff-base condensation reaction of 1,5-diaminonaphthalene and 4-(dimethylamino)benzaldehyde in the presence of ethanol. A series of aromatic polyimides bearing naphthalene and -CH=N-groups were synthesized from the diamine with five kinds of commercial dianhydrides via a conventional one-stage process. The resulting naphthalene based polyimides (NBPs) showed good solubilities in N-methyl-2-pyrrolidone and m-cresol. NBPs had glass-transition temperatures at 139-174 degrees C and 10% weightloss temperatures above 430 degrees C in nitrogen atmospheres. Excellent properties of NBPs are attributed to the incorporation of the naphthalene and -CH=N- group in 1,5-bis(p-dimethylaminophenylimino)naphthalene. Moreover, chemically prepared polyimides were used for immobilization of glucose oxidase (GOx). The amperometric responses of the NBPs-GOx-Pt electrodes toward glucose were examined at a potential of 0.7 V in PBS solution by means of time-base (TB) technique. Results show that NBPs bearing -O- group membrane (PI-3) has many advantages in the immobilization of glucose oxidase because of its strong adherence to electrode surface and chemical stability and selectivity. Copyright (C) 2010 John Wiley & Sons, Ltd.Öğe Synthesis, characterization of phosphine oxide-containing polyimides and their use as selective membrane for dopamine(Springer, 2008) Koeytepe, Sueleyman; Pasahan, Aziz; Ekinci, Ergun; Alici, Buelent; Seckin, TurgayTris-(p-aminophenoxy)phosphineoxide, t-APPO, was prepared from 4-nitrophenol and POCl3, followed by hydrogenation. A series of polyimides prepared from t-APPO and the corresponding dianhydrides by two-stage polycondensation method was characterized by Fourier Transform Infrared Spectrometer (FTIR), GPC, thermal analysis and physical methods. Moreover, in order to check the permeation properties of the resulting polyimide film, the selectivity of the polyimide-coated electrode toward electroactive species (ascorbic acid and dopamine) was examined by means of cyclic voltammetry (CV), differential pulse voltammetry (DPV) and time-base amperometric measurement (TB) techniques. As a result, it has been found that polyimide electrode showed selective permeation for dopamine while blocking the permeation of ascorbic acid through film. Therefore, it has been claimed that phosphine oxide-containing polyimide electrode can be used as a dopamine-selective membrane in the presence of ascorbic acid.Öğe Synthesis, characterization of poly(4, 4?-diaminophenylethanepyromellitimide) and its use as immobilized enzyme polyimide membrane(Sage Publications Ltd, 2011) Pasahan, Aziz; Koytepe, Suleyman; Ekinci, ErgunA novel polyimide prepared from pyromellitic dianhydride (PMDA) and 1,2-bis(4-aminophenyl)ethane was characterized by Fourier transform infrared spectrometer and gel permeation chromatography. Thermal properties of the poly(4,4'-diaminophenylethane-pyromellitimide) (PDP) were evaluated by differential scanning calorimetry, differential thermal analysis and thermogravimetry. The PDP exhibited high decomposition temperature T(d) (degrees C), good thermal stability and good adhesive properties. Moreover, that the possibility of whether the chemically-prepared polyimide film could be used as a membrane for immobilization of glucose oxidase (GOx) was investigated. The amperometric response of the PDP/GOx/Pt electrode to hydrogen peroxide, formed as the product of enzymatic reaction, was measured at a potential of 700 mV (vs. SCE) in phosphate buffer solution by means of the TB technique. The amperometric glucose sensor was very high R-value (0.9995). The structure of the GOx micelles contained in polyimide membrane was observed by scanning electron microscopy. From the amperometric responses, it was also demonstrated that PDP film could be used as a solid-state immobilized enzyme polyimide membrane for biosensor design because of its strong adherence to electrode surface and chemical stability.
