Yazar "Ekinci, E" seçeneğine göre listele
Listeleniyor 1 - 15 / 15
Sayfa Başına Sonuç
Sıralama seçenekleri
Öğe Electrochemical poly(1,3-phenylenediamine) synthesis as enzyme immobilization media(John Wiley & Sons Inc, 1998) Ekinci, E; Ogunc, ST; Karagozler, AEElectrochemical polymerization of the 1,3-phenylenediamine in the presence of glucose oxidase with KCl aqueous electrolyte at a potential of 0.800 V versus Ag-AgCl produces adherent poly(1,3-phenylenediamine) containing enzyme (glucose oxidase) film on a platinum electrode. Polymeric sensor prepared in this one-step procedure can be used to determine hydrogen peroxide formed as the result of the enzymatic reaction between glucose and glucose oxidase in the presence of O-2. The amperometric responses of the resultant enzyme electrode to glucose were rapid, reaching steady-state values within 4-5 s, and there was a linear relationship between glucose concentration and obtained current up to 6 mM. Polymeric sensor was stable for more 3 months. The glucose selectivity of enzyme electrode was determined in the presence of some interfering substances, such as lactose, sucrose, urea, uric acid, paracetamol, and ascorbic acid. Also, the effects of buffer concentration, storage conditions, and temperature on the steady-state amperometric responses were studied. Moreover, the Arrhenius activation energy for the enzymatic reaction was calculated. (C) 1998 John Wiley & Sons, Inc.Öğe Electrochemical preparation of poly(o-toluidine) film and its application as a permselective membrane(Wiley, 1999) Özden, M; Ekinci, E; Karagözler, EPoly(o-toluidine) films were electrochemically synthesized on Pt electrodes at a constant potential (0.75 V versus Ag/AgCl) from a deoxygenated aqueous solution of 0.1M toluidine dissolved in 0.1M KCl. To form permselective polymeric film electrodes, poly(o-toluidine) films at different thicknesses were prepared by varying the amount of charge consumed during electrochemical polymerization. Then, experimental parameters (e.g., concentrations of monomer and electrolyte and pH of the phosphate buffer salt solution) affecting the polymeric film thickness were optimized. Permeation of the various electroactive and nonelectroactive species such as ascorbic acid, oxalic acid, hydrogen peroxide, lactose, sucrose, and urea through the optimized poly(o-toluidine)-coated electrodes was investigated using a chronoamperometric technique. From experimental results, it was found that a poly(o-toluidine)-coated electrode permitted the oxidation of hydrogen peroxide and prevented the permeation of the mentioned electroactive and nonelectroactive species. in other words, it was seen that this polymeric electrode responded to only hydrogen peroxide selectively. Thus, it has been claimed that a poly(o-toluidine)-coated Pt electrode can be used as a permselective polymeric membrane to overcome interference problems occurring in the hydrogen peroxide-based biosensor applications. (C) 1999 John Wiley & Sons, Inc.Öğe Electrochemical synthesis and optimization of poly(4-methoxyphenol) film as a sensor material(John Wiley & Sons Inc, 1998) Ozden, M; Ekinci, E; Karagozler, AEThis article describes that electrochemical polymerization of 4-methoxyphenol in the presence of enzyme glucose oxidase produces adherent polymeric films containing the active enzyme onto the surface of platinum electrodes. Polymeric electrodes prepared in this one-step procedure can be operated for the glucose determination. The effects of the electrochemical polymerization parameters (for example, concentrations of monomer, electrolyte, and enzyme; film thickness; and polymerization potential) on the electrode preparation and the effects of amperometric measurement parameters (for example, pH, temperature) on the amperometric responses to the glucose of the prepared electrodes were systematically investigated, and optimal values were determined. Furthermore, glucose specificity and storage stability of the enzyme electrode were investigated. (C) 1998 John Wiley & Sons, Inc.Öğe Electrochemical synthesis and sensor application of poly(1,4-diaminobenzene)(Elsevier Science Sa Lausanne, 1996) Ekinci, E; Karagozler, AA; Karagozler, AEThis paper describes a novel polymeric matrix, poly (p-phenylenediamine), as glucose oxidase entrapment media for amperometric glucose determination. The glucose sensor was constructed in a one-step procedure by anodic electropolymerization of p-phenylenediamine and concomitant incorporation of glucose oxidase at a potential of 0.7 V versus Ag/AgCl. Results show that the new glucose sensor has a linear range up to 6 mM, fast response time (less than 4 s) and high sensitivity. The specificity of the enzyme electrode for possible interfering species such as lactose, sucrose and urea was tested, and no discernible anodic signal was detected above the background current. Moreover, the effects of pH and temperature on the amperometric response were systematically investigated and the activation energy for enzymatic reaction was calculated as 41 kJ/mol. Also, the biosensor was found to be stable for more than 30 days.Öğe Investigation of polymerization parameters affecting dopamine selectivity of a polymeric membrane(Springer-Verlag, 2000) Ekinci, E; Erdogdu, G; Karagözler, AEBy means of electrochemical oxidative polymerization, poly (1,3-phenylenediamine) films on a gold electrode were prepared at a potential of 0.8 V. The permeation properties of polymeric films at the different thickness were investigated by cyclic and differential pulse voltammetry techniques. Voltammetric studies showed that polymeric film at the 1.2 mC thickness exhibited selective permeation for dopamine while rejecting ascorbic acid. Then, all the polymerization parameters affecting the permselective characteristics were systematically investigated and the optimal values were determined. Moreover, stability of polymeric membrane was examined. The results showed that polymeric membrane, owing to permselective character, could be used as a dopamine selective membrane.Öğe Poly (4-methoxyphenol) film as a galactose-sensing material(Pergamon-Elsevier Science Ltd, 2004) Ekinci, E; Pasahan, APoly (4-methoxyphenol)-galactose oxidase biosensor for galactose is reported. This amperometric biosensor was prepared in a one-step procedure by electrochemical polymerization of the relevant monomer in the presence of galactose oxidase on Pt electrode surface in a KCl solution at potential of 0.6 V vs. Ag/AgCl. From the steady-state amperometric responses to galactose of the resulting polymeric biosensor, its sensor characteristics such as feasibility of preparation, linear range, response time, selectivity and stability were evaluated. (C) 2004 Elsevier Ltd. All rights reserved.Öğe Preparation and electrochemical behavior of dopamine -: selective polymeric membrane(Springer Verlag, 2000) Erdogdu, G; Ekinci, E; Karagözler, AEo-toluidine was polymerized electrochemically using constant-potential electrolysis at a gold electrode surface. Electrochemical behavior of dopamine and ascorbic acid at the polymer electrode prepared in this manner was examined by cyclic and differential pulse voltammetry techniques. The influence of chemical and electrochemical variables on dopamine selectivity of the polymer electrode was systematically investigated and the optimal values for each parameter were determined. Experimental results showed that optimized polymeric membrane exhibited selectivity for dopamine while blocking ascorbic acid. Therefore, it is claimed that poly (o-toluidine) film can be used as a dopamine-selective polymeric membrane in the presence of ascorbic acid.Öğe Preparation and properties of polybenzidine film-coated electrode as an H2O2 selective polymeric material(Wiley, 1998) Ekinci, E; Ozden, M; Turkdemir, MH; Karagozler, AEBy means of electrochemical polymerization, polybenzidine-modified electrodes were prepared in an aqueous monomer solution at a potential of 0.7 V versus Ag/AgCl. The permselective character of the polybenzidine electrode prepared in a one-step procedure was examined for electroactive (ascorbic acid, oxalic acid, and hydrogen peroxide) and nonelectroactive (lactose, sucrose, and urea) species. Influence of the various parameters on the permselective properties of the polybenzidine membrane was systematically investigated and the optimal values for these parameters were determined. It has been found that polybenzidine membrane showed selective permeation for hydrogen peroxide while blocking the permeation of electroactive and nonelectroactive interferents through film. In brief, it is claimed that this polybenzidine film can be used as a coating material to prevent interferences in electrochemical biosensor applications. (C) 1998 John Wiley & Sons, Inc.Öğe The preparation and sensor application of poly(p-aminophenol)(Vch Publishers Inc, 1996) Ekinci, E; Karagozler, AA; Karagozler, AEAn amperometric biosensor for glucose based on a novel polymeric matrix is described. The sensor was prepared by electrochemical polymerization of p-aminophenol in the presence of glucose oxidase on Pt substrates in a KCl solution at a potential of 0.6 V (vs. Ag/AgCl). The chronoamperometric response of poly(p-aminophenol)-glucose oxidase biosensor to hydrogen peroxide formed as the result of enzymatic reaction was measured at a potential of 0.7 V (vs. Ag/AgCl) in PBS solution. It was shown that a biosensor prepared by this onestep procedure has a linear range up to 6 mM glucose, a response time less than 5 s and a lifetime around 15 days. The sensitivity of the electrode was superior to that of much publicized polypyrrole based glucose oxidase electrode. Also, the substrate selectivity of PAP/GOx electrode was tested for coexisting substances such as lactose, sucrose, urea, paracetamol, uric and ascorbic acid and no discernible anodic response was observed above the background current.Öğe Preparation and sensor properties of poly (o-toluidine) film(Springer Verlag, 1999) Ekinci, EAn amperometric biosensor for glucose was constructed in a one-step procedure by the electropolymerization of o-toluidine in the presence of glucose oxidase on Pt substrates in KCl aqueous electrolyte at a potential of 0.5 V vs Ag / AgCl. The amperometric responses of the prepared polymeric biosensor to the glucose were measured at a potential of 0.7 V in PBS solution. Results showed that this polymeric sensor exhibited a fast amperometric response time (4-5 s) and a linear range up to 6 mM glucose with poor stability. Also, it was seen that biosensor responded successfully to glucose injections in the presence of some interfering species such as lactose, sucrose and urea.Öğe Preparation, characterization and H2O2 selectivity of hyperbranched polyimides, containing triazine(Springer, 2005) Ekinci, E; Emre, FB; Köytepe, S; Seçkin, TNovel polyimides based on aromatic dianhyride and various hexahydrotriazine monomers were synthesized via two-stage solution polycondensation method. The resulting polyimides were characterized by solubility, viscosity, density, spectroscopic and thermal analysis methods. The results showed that polyimides soluble in polar solvents and had inherent viscosities ranging from 1.92 to 2.32 dL/g. The glass transition temperatures were 315 and 344 degrees C, and the 10% weight loss Then, polyimide-modified electrodes were prepared for the selective determina-temperatures were above 604 and 628 degrees C. Then, polyimide-mofified electrodes were prepared for the selective determination of hydrogen peroxide. The electrochemical behavior of the resulting polyimide film electrodes to the electroactive and non-electroactive species such as ascorbic acid, oxalic acid, hydrogen peroxide, lactose, sucrose and urea was examined by CV, DPV and TB techniques. From the obtained findings, it was shown that polyimide-coated electrode (PI-2) was only permitted to hydrogen peroxide among the species examined. As a result, it is claimed that polyimide electrode could be used as a selective membrane for hydrogen peroxide.Öğe Preparation, optimization, and voltammetric characteristics of poly(o-phenylenediamine) film as a dopamine-selective polymeric membrane(John Wiley & Sons Inc, 2001) Ekinci, E; Erdogdu, G; Karagözler, AEPoly(o-phenylenediamine) films were electrochemically prepared on gold electrodes from the corresponding monomer in an aqueous solution at a constant potential. The polymeric films prepared in this one-step procedure were found to be thin and insoluble in the aqueous solution. Cyclic and differential pulse voltammetric techniques were used to examine the permeation properties of ascorbic acid and dopamine at the resultant polymeric film electrode. Then, the effects of the chemical and electrochemical variables (e.g., film thickness, polymerization potential, concentrations of monomer and electrolyte) on the permselectivity characteristics of the polymeric film were systematically investigated and the optimal values for each parameter were determined. Furthermore, it was found that the optimized polymer electrode was found to be stable for the successive runs. As a result, it is claimed that poly(o- phenylenediamine) film can be used as a dopamine-selective polymeric membrane. (C) 2000 John Wiley & Sons, Inc.Öğe Synthesis and optimization of permselective polymer (polyindoline) film(Springer Verlag, 1998) Ozden, M; Ekinci, E; Karagozler, AEA polyindoline permselective polymer film was readily synthesized by an electrochemical polymerization of indoline in an aqueous solution of KCl at a potential of 0.4 V vs Ag/AgCl. The amperometric responses of the polyindoline film-coated platinum electrodes to electroactive (ascorbic acid, oxalic acid and hydrogen peroxide) and non-electroactive (lactose, sucrose and urea) substances were measured at a potential of 0.7 V. Effects of various variables such as film thickness, concentrations of monomer and electrolyte, and pH on the permselective behavior of the polymeric membrane were systematically investigated and the optimal values were determined. It was found that permselective polyindoline-coated electrodes prepared in this one-step procedure permitted hydrogen peroxide oxidation while it prevented interference due to oxidizable species such as ascorbic acid and oxalic acid. As a result, it is believed that this polymeric membrane, owing to its permselective character, can be used as the protective material in the construction of hydrogen peroxide-based biosensors.Öğe Synthesis, characterization and dopamine selectivity of 1,4-bis(3-aminopropyl)piperazine -: Containing polyimide(Springer, 2004) Pasahan, A; Köytepe, S; Ekinci, E; Seçkin, TA novel polyimide prepared from 1,4-bis(3-aminopropyl) piperazine and pyromellitic dianhydride (PMDA) was characterized by thermal, FTIR, GPC and microanalysis techniques. Thermal properties of the polyimide were evaluated by differential scanning calorimetry (DSC), differential thermal analysis (DTA) and thermogravimetry (TGA). Moreover, platinum electrodes were covered with this polyimide and permeation properties of the resulting polyimide-coated electrodes to dopamine and ascorbic acid were examined by electrochemical method. On the basis of the permselectivity data obtained, it was found that the polyimide-coated electrode exhibited selective permeation for dopamine while blocking ascorbic acid.Öğe Synthesis, characterization and H2O2-sensing properties of pyrimidine-based hyperbranched polyimides(Pergamon-Elsevier Science Ltd, 2005) Köytepe, S; Pasahan, A; Ekinci, E; Seçkin, TA series of hyperbranched polyimides having pyrimidine core in the backbone was prepared by solution polycondensation of pyromellitic dianhydride (A(2) type) and 2,4,6-triaminopyrimidine (B-3 type). The resulting polyimides were characterized by IR, GPC, DTA, DSC, TGA, density and viscosity measurement. The results showed that polyimides were obtained in 82-86 % yield, had inherent viscosities of 1.58-1.87 dL/g and highly thermal stability. From the solubility tests, it was found that all the polyimides were soluble in NMP, DMAc and DMSO at room temperature. In addition, because of their interesting film properties, attempts were made to prepare H2O2-sensing polyimide material. For this reason, selectivity of film-coated electrodes obtained from the chemically prepared hyperbranched polyimides toward electroactive (ascorbic acid, oxalic acid and hydrogen peroxide) and non-electroactive (lactose, sucrose and urea) species was examined by means of CV, DPV and TB techniques. From the electrochemical data obtained, it has been demonstrated that polyimide (HPI-2) film responded to only hydrogen peroxide among the species examined. In other words, it has been claimed that the mentioned polyimide-coated electrode can be used as H2O-selective membrane in the presence of the electroactive and non-electroactive interferents. (C) 2004 Elsevier Ltd. All rights reserved.
