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Öğe Çevre ve klinik kimya analizleri için iletken polimerlerle modifiye edilmiş elektrokimyasal sensörlerin geliştirilmesi(1994) Karagözler, A. Alev; Titretir, Serap; Karagözler, A. Ersin; Ekinci, Ergun; Erdoğdu, GamzeBu projenin ilk aşamasında; pirol, p-aminofenol, fenilendiamin, 4-metoksifenol ve anilin gibi monomerlerin, enzim (glukoz oksidaz) varlığında sabit potansiyeldeki elektropolimerizasyonuyla değişik polimerik matrisli biyosensörler hazırlanmış ve bu biyosensörlerin glukoza karşı seçicilik, duyarlılık, doğrusallık, yanıt süresi ve kararlılık gibi sensör karakteristikleri sistematik bir yaklaşımla incelenmiştir Elde edilen sonuçlardan sensörlerin glukoz ölçümlerinde kullanılabilecek kadar doğrusal bir yanıt aralığına, hızlı bir yanıt süresine ve özellikle m-fenilendiamin polimeri durumunda tatminkar bir kararlılığa sahip oldukları gözlenmiştir. Bununla birlikte anılan polimerik sensörlerin en büyük dezavantajları interferantlardan etkilenmeleridir. İnterferans problemlerinin yenilebilmesi amacıyla seçimli geçirgen elektropolimerik materyallerin hazırlanması konusu üzerine yoğunlaşmıştır. Bu amaçla elektroaktif hidrojen peroksiti geçiren fakat girişime sebep olan askorbik asit ve okzalik asit gibi elektroaktif ve laktoz, sukroz ile üre gibi elektroaktif olmayan interferantlardan etkilenmeyen seçici geçirgen polibenzidin, poliindolin ve poli(o-toludin) polimerleri hazırlanarak geçirgenlik özellikleri optimize edilmiştir. İkinci aşamada; katekol, hidrokinon, dopamin, askorbik asit, epinefrin, asetaminofen ve p-aminofenolün diferansiyel puls voltametrisi ile poli-3-metiltiyofen, polipirol, polianilin ile modifiye edilmiş elektrotlarda elektrokimyasal davranışları incelenmiştir. Bu moleküllerin voltametrik analizine zemin elektrolit tür ve pH'sı ile film kalınlığının etkisi sistematik olarak araştırılmıştır. Ayrıca, dopamin ve askorbik asit ikili test karışımının elektrokimyasal davranışları çevrimli voltametri ve her bir bileşenin analizi diferansiyel puls voltametrisi ile incelenerek anılan polimerlerin elektrokataliz yetenekleri karşılaştırılmıştır. Polimer kaplı elektrotlar, ayrıca, yukarıda anılan moleküllerin flow injection analizinde amperometric detektör olarak kullanılmıştır. Polimer elektrotların yanıtının çıplak platininkiyle karşılaştırıldığında 5-16 kez daha yüksek olduğu görülmüştür. Benzer şartlar altında hazırlanan elektrotlarla elde edilen her üç polimer elektrodun da elektrokatalitik aktivite göstermekte olduğunu; ancak, poli-3-metiltiyofenin kararlılığının diğer elektrotlardan daha iyi olduğunu göstermiştir.Üçüncü aşamada ise; iletken polimerlerden poli-3-metiltiyofen ile modifiye edilmiş altın veya platin elektrotlarla bazı anyonik türlerin sıyırma voltametrik analizinin mümkün olup olmayacağı araştırılmıştır. İyodürün derişik zemin elektrolit türlerinde ve pH'larda bu elektrot üzerindeki davranışı dönüşümlü voltametri ile incelendiğinde polimer elektrotla sodyum sülfat içerisinde elde edilen voltamogramların çıplak elektrottakine en yakın olduğu görülmüştür. Sıyırma voltametrik analizden önce filmin seçilen zemin elektrolit içinde sıyırma voltametrik koşullarda şartlandırılması gereği ortaya çıkmıştır. Çalışmada anılan polimer elektrotla iyodürün $10^7$ M kadar düşük derişiminin sıyırma analizinin mümkün olduğu gösterilmiş, sıyırma analiz pik yükseklikleri üzerine film kalınlığının ve toplama süresinin etkileri incelenmiştir. Ferro/ferri siyanür redoks çifti ve antimon (III) ($SbO_{3^{3-}}$) iyonunun voltametrik sıyırma analiz imkanları araştırılmış, antimon (III) anılan elektrotta elektroaktif olmadığı, ferro/ferri siyanürün ise elektroaktif olmasına rağmen polimer filme katılmadığı ve böylece sıyırma öncesinde elektrotta toplamanın mümkün olmadığı görülmüştür.Öğe DNA base sensor characteristics of polymeric-nanocomposite electrode(Taylor & Francis As, 2016) Ayazli, Sezen Kursun; Ekinci, Bilge Zabci; Ekinci, ErgunThe electrochemical synthesis of polyamline films was carried out by potential sweep method in sulfuric acid solution at the glassy carbon electrode. The electrocatalytic behavior to DNA bases (adenine and guanine) uric acid, and dopamine of polyaniline nanocomposite sensor modified with nano-gold particles was investigated by DPV technique. By systematically examining the effects of the possible parameters affecting he electrocatalytic performance of the relevant sensor, the optimal value for the each parameter was determined. The detailed electrocatalytic studies of the optimized sensor revealed that this sensor could be used as DNA base sensor for guanine in the presence of adenine, dopamine, and uric acid. Moreover, the performance of the relevant sensor in thermally denatured fish sperm DNA was quite satisfactory. [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 Elektrokimyasal sensör materyali olarak polimerlerin sentezi ve fizikokimyasal özelliklerinin incelenmesi(İnönü Üniversitesi, 1995) Ekinci, ErgunHI ÖZET Çalışmanın amacı, amperometrik olarak glukoz tayini için glukoz oksidaz (GOD) immobilizasyon ortamı olarak yeni polimerik matriksler olan poli(p-aminofenol) ve poli(l,4- diaminobenzen) polimerleri sentezlemek ve sensör karakteristiklerini incelemektir. Glukoz sensörleri, glukoz oksidaz varlığında Ag/AgCl'e karşı 0.6 veya 0.7V'da KC1 çözeltisi içerisindeki monomerin [(p-aminofenol) yada (1,4-diaminobenzen)] elektrokimyasal polimerizasyonu ile hazırlandı. Kronoamperometrik glukoz yanıtı, hazırlanan poli(p- aminofenol)-God ya da poli(l,4-diaminobenzen)-God sensörün, enzimatik reaksiyon sonucu meydana gelen hidrojen peroksiti yükseltgemek amacıyla 0.7 V potansiyelde tutulmasıyla ölçüldü. Elde edilen sonuçlar, yeni sensörlerin 6 mM glukoza kadar doğrusal bir yanıta, hızlı bir yanıt süresine (<4 sn) ve yüksek duyarlılığa sahip olduğunu göstermektedir. Sensörlerin, laktoz, sukroz, üre, askorbik asit, ürik asit ve parasetamol gibi farklı maddelere karşı seçiciliği incelendi ve poli(p-aminofenol)-God için parasetamol hariç zemin akımı üzerinde herangi bir anodik sinyal gözlenmedi. Aynı zamanda, sensörlerin yanıt karakteristikleri üzerine pH ve sıcaklık etkileri sistematik olarak incelenmek suretiyle optimum değerler bulundu. Bundan başka, hem poli(l,4-diaminobenzen)-God ve hemde poli(p-aminofenol)-God elektrotların aktivasyon enerjileri ve kinetik parametreleri gibi fizikokimyasal özellikleri incelendi. Çalışmanın diğer kısmında, nafyon (polimer) bazlı amperometrik okzalat elektrot hazırlandı ve hazırlanan okzalat elektrodun okzalik asit için sensör karakteristikleri incelendi. Sonuç olarak, hazırlanan polimerik materyallerin sensör özellikleri yayınlanan diğer sensörlerle karşılaştırıldı ve üstün yanları vurgulandı.Öğe Elektropolimerik ürik asit sensörlerinin geliştirilmesi(2010) Ekinci, Ergun; Zabcı, Bilge Ekinci; Paşahan, Aziz; Kurşun, Sezen[Abstract Not Available]Öğe Immobilization of Glucose Oxidase in GLYMO/MTEOS Sol-Gel Film for Glucose Biosensor Application(Slovensko Kemijsko Drustvo, 2012) Demirkiran, Nizamettin; Ekinci, ErgunAn 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 ob served that the amperometric response of the enzyme electrode was linear for gluco se concentrations in the range from 2 to 10 m M. The response time of the biosensor to reach a steady-state cur rent 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 ob served 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 degrees C.Öğe IMMOBILIZATION OF GLUCOSE OXIDASE IN SILICA SOL-GEL FILM FOR APPLICATION TO BIOSENSOR AND AMPEROMETRIC DETERMINATION OF GLUCOSE(Soc Chilena Quimica, 2012) Demirkiran, Nizamettin; Ekinci, Ergun; Asilturk, MeltemIn 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 degrees C.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 characterization of an aromatic polyimide and its use as a selective membrane for H_2O_2(Turkish Journal of Chemistry, 2006) Ekinci, Ergun; Köytepe, Süleyman; Paşahan, Aziz; Seçkin, TurgayÖz: Başlık (İngilizce): Öz (İngilizce): Selectivity behavior to electroactive and non-electroactive substances of a polyimide prepared from 2,2'-dimethyl-4,4'-diaminobiphenyl and the corresponding dianhydride was examined by electrochemical methods. From the excellent electrochemical findings obtained, it was observed that polyimide film was only permeable to hydrogen peroxide among the substances examined. Therefore, it is claimed that the mentioned polymeric film can be successfully used as a hydrogen peroxide-selective membrane in the presence of electroactive and non-electroactive interferents.Öğe Preparation and optimization of conducting polymer(polypyrrole)as a glucose sensor(Turkish Journal of Chemistry, 1995) Ekinci, Ergun; Özden, Mustafa; Karagözler, A. Alev; Türkdemir, Haluk M.; Karagözler, A. AlevPreparation and optimization of conducting polymer(polypyrrole)as a glucose sensor Öz: Anahtar Kelimeler: Konu Alanı: Fen > Mühendislik > Mühendislik, Kimya Belge Türü: DergiMakale Türü: DiğerErişim Formatı: Erişime AçıkÖğe 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 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 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.Öğe Synthesis, characterization of pyridine-based polyimides and their use as glucose oxidase immobilization media(Walter De Gruyter Gmbh, 2012) Pasahan, Aziz; Koytepe, Suleyman; Ekinci, ErgunA novel diamine monomer, containing 2,6-diaminopyridine, bis-p-dimethylaminophenyl-2,6-pyridine (S26DAP), was prepared from 4-(dimethylamino)benzaldehyde and 2,6-diaminopyridine. The monomer was characterized by FT-IR, NMR and elemental analyzer. The monomer was then utilized to prepare polyimides with dianhydrides such as pyromellitic dianhydride (PMDA), 3,3',4,4'-benzophenonetetracarboxylic dianhyride (BPDA), 4,4'-oxydiphthalic anhydride (ODPA) and 3,3',4,4'-biphenyltetracarboxylic dianhydride (BTDA) by the one-step method; synthesis of polyimides, followed by thermal imidization. The polyimides were characterized by FT-IR, GPC with intrinsic viscosity and adhesive properties also being evaluated. The polyimides exhibited high T-g (degrees C) (186-209 degrees C), good thermal stability and good adhesive properties. Medium to high molecular weight polymers were attained, with inherent viscosities near or higher than 1.05-1.32 dL/g, the solubility in dipolar aprotic solvents of the polyimides were much better than that of the aromatic polyimides. Furthermore, chemically synthesized polyimides were used for immobilization of glucose oxidase (GOx). The amperometric responses of the prepared GOx-polyimide-coated electrodes to glucose were examined at a potential of 0.7 V in PBS solution by means of TB technique. The results show that polyimide (S26DAP-PI-4) can be used for immobilization of glucose oxidase.
