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Öğe Electrochemical poly(1,3-phenylenediamine) synthesis as enzyme immobilization media(John Wiley and Sons Inc., 1998) Ekinci E.; Ö?ünç S.T.; Karacözler A.E.Electrochemical 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 O2. The amperometric responses of the resultant enzyme electrode to glucose were rapid, reaching steadystate 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. © 1998 John Wiley & Sons, Inc.Öğe Electrochemical Preparation of Poly(o-toluidine) Film and Its Application as a Permselective Membrane(John Wiley and Sons Inc., 1999) Özden M.; Ekinci E.; Karagözler E.Poly(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. © 1999 John Wiley & Sons, Inc.Öğe Immobilization of glucose oxidase in GLYMO/MTEO sol-gel film for glucose biosensor application(2012) Demirkiran N.; Ekinci E.An electrochemical biosensor was developed by using the sol-gel coating solution. The modified platinum electrode used in the study was constructed by immobilization of glucose oxidase under a layer of sol-gel film. The coating solution was prepared by using GLYMO, and MTEOS. Electrochemical measurements were carried out amperometrically by determining hydrogen peroxide produced by the enzymatic reaction between glucose and glucose oxidase. It was observed that the amperometric response of the enzyme electrode was linear for glucose concentrations in the range from 2 to 10 mM. The response time of the biosensor to reach a steady-state current value was approximately 80 s. The glucose selectivity of the biosensor was determined in the presence of some interfering substances, such as lactose, sucrose, urea, uric acid, oxalic acid, and ascorbic acid. It was observed that the interfering molecules did not cause any observable signal. The stability of the sensor was investigated, and it was found hat the initial sensor response decreased approximately 44% over a period of 30 days of storage in dry state at 4 °C.Öğe Immobilization of glucose oxidase in silica sol-gel film for application to biosensor and amperometric determination of glucose(2012) Demirkiran N.; Ekinci E.; Asiltürk M.In this study, an electrochemical biosensor was developed by using a sol-gel coating solution. The modified platinum electrode used in the study was constructed by immobilization of glucose oxidase under a layer of sol-gel film. The sol-gel coating solution was prepared by using GLYMO, TEOS, and MTEOS. Electrochemical measurements were carried out amperometrically by determining hydrogen peroxide produced by the enzymatic reaction between glucose and glucose oxidase. The amperometric responses of the resulting enzymatic electrode to glucose were rapid. It was observed that the amperometric response of the enzymatic electrode was linear for glucose concentrations in the range from 2 to 18 mM with 50 s response time. LOD and LOQ for the enzymatic electrode were calculated to be 0.055 mM and 0.184 mM, respectively. It was determined that the developed biosensor had an acceptable reproducibility. The selectivity of the biosensor was determined in the presence of some interfering substances, such as lactose, sucrose, urea, uric acid, oxalic acid, and ascorbic acid. The stability of the biosensor was investigated, and it was found that the sensor response decreased by 59% of its initial response over a period of 30 days of storage in dry conditions at 4 °C.Öğe The mechanical and physical properties of unfired earth bricks stabilized with gypsum and Elazığ Ferrochrome slag(Elsevier B.V., 2017) Türkmen İ.; Ekinci E.; Kantarcı F.; Sarıcı T.During the last few years, an increasing interest has been appeared for earth as a building material. Earth-based materials have been studied because of energy efficiency and ecologically sustainability. The chromite deposits, 10% of the world reserves, are processed in Elazığ Ferrochrome Factory in Eastern of Turkey. Elazığ Ferrochrome slag (EFS) as a by-product of the factory is produced roughly 50,000 tons in a year. The disposal, removal and storage of this by-product is a serious problem. Therefore, the utilization of this waste material in building applications is very important. The aim of this work is to investigate effects of gypsum and EFS additives on mechanical and physical properties of unfired earth brick (UEB) materials in order to assess their potential advantages in building applications. The earth material was characterized by laboratory tests. Four different UEB samples were produced by using different compositions of earth, gypsum, EFS and straw fibers. Compressive strength, water absorption coefficient, drying shrinkage, ultrasonic pulse velocity (UPV) and density of the prepared UEB samples were determined. The experimental findings have showed that the usage of gypsum and EFS in stabilizing process of UEBs was advantageous. © 2017Öğe Optimization of production parameters of alkali-activated concrete(Elsevier, 2021) Kantarci F.; Türkmen I.; Ekinci E.Concrete is a frequently preferred construction material which is used in many fields and applications such as buildings, roads, tunnels, bridges, dams and harbors. Portland cement (PC), the main component of concrete, is a leading building material all over the world with an annual production capacity of 4 billion tons and a growth rate of 4%. About 7% of total CO2 emissions originate from production of PC. It is predicted that 17% of total CO2 emissions will come from PC production in the next few years. Scientists have been making effort to overcome environmental and economic problems caused from PC production. Alkali-activated binders (AABs) emerging as a result of these efforts were originally proposed by French researcher Davidovits for aluminosilicate-based inorganic polymers. AABs are semicrystalline three-dimensional polymers synthesized by activation of high alkali solution with raw material rich in silicon and aluminum. Alkali-activated concrete (AAC) has been applied in various applications such as ready mixed concrete, reinforced concrete, concrete pipes, lightweight concrete. While most of the studies have focused on the reaction mechanisms and microstructures of AABs, relatively few studies have been carried out on the mix designs of AAC. However, engineering properties of AABs depend on raw materials, alkali activator type and alkali activator content, curing parameters, water content and mixing parameters. The aim of this chapter is to comparatively asses the production parameters of AACs in order to provide an understanding of the current findings and develop a general guideline. © 2022 Elsevier Ltd All rights reserved.
