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Öğe Alkali metals (Na, K) doped ZnO/CuO composite films for real-time tracking of sweat loss(Elsevier Sci Ltd, 2023) Sahin, B.; Ozyilmaz, G.; Kaya, T.Real-time sweat rate monitoring provides clinically proper directives for preventive medicine and dis-ease diagnosis. This research represents an attempt to develop a semiconductor-based nanostructured sensor for monitoring sweat rate using a ZnO/CuO composite thin film. A series of alkali metals (sodium, Na; potassium, K) doped ZnO/CuO composite samples were fabricated on soda lime glass substrates by the Successive Ionic Layer Adsorption and Reaction method. The sweat solution sensing response characterization exhibited promising sensing behavior under room conditions. The Na-and K-doped samples showed a pronounced response at low and high concentrations of the sweat solution. While the undoped composite film responds to the high concentration sweat solution (117.90 mM) with a sensi-tivity of 4.10, this value increases up to 9.15 for the 2.0% Na-doped samples. In addition, the response time shortens from 6 s to 4 s for 2.0% Na substitutions. Pristine, 2.0% Na and 2.0% K-substituted ZnO/CuO composites exhibit great linearity with linear regression ranges, R2, of 0.958, 0.971, and 0.984, respec-tively. We concluded that doping of ZnO/CuO composites with alkali metals Na and K is a good candidate for real-time tracking of sweat loss as biological evidence.(c) 2023 Elsevier Ltd. All rights reserved.Öğe Electrochemical synthesis of poly (aniline-co-o-anisidine) coatings on brass: corrosion protection properties(Taylor & Francis Ltd, 2009) Ozyilmaz, A. T.; Ozyilmaz, G.; Colak, N.Poly (aniline-co-o-anisidine) films were coated on Cu-40% brass electrodes using cyclic voltammetric conditions in a sodium oxalate solution with 0.06M aniline and 0.06M o-anisidine monomers at applied scan rates of 20 and 50 mV s(-1). Using this procedure, the surface of the electrodes was clearly covered with a black copolymer layer of strongly adherent homogeneous characteristics. In order to evaluate the corrosion performance of copolymer coated (CuZn/PANI-co-POA) and uncoated electrodes in 3.5% NaCl, AC electrochemical impedance spectroscopy, anodic polarisation plots and open circuit potential-time curves were used. The copolymer films exhibited significant protection efficiency against the attack of corrosive agents and reduced drastically the corrosion rate of the brass.Öğe Glucose Oxidase-polypyrrole Electrodes Synthesized in p-Toluenesulfonic Acid and Sodium p-Toluenesulfonate(Pleiades Publishing Inc, 2011) Ozyilmaz, G.; Ozyilmaz, A. T.; Can, F.Amperometric glucose biosensors have been developed based on entrapment on platinum (Pt) electrode using cyclic voltammetry technique in glucose oxidase (GOD) and pyrrole containing p-toluene-sulfonic acid (pTSA) or sodium p-toluenesulfonate (NapTS) as supporting electrolyte solutions. Both of electrolyte solutions were suitable media for the formation and deposition of polypyrrole-GOD (PPy-GOD) layers on Pt substrate. Pt/PPy-GOD electrodes brought about in different morphological properties as well as different electrochemical and biochemical response. The highest responses obtained in pTSA and NapTS electrolytes were observed at pH of 4.5 and 7.0 for Pt/PPy-GOD electrodes, respectively. While linearity was observed between 0.0-1.0 mM glucose substrate for both electrodes, I-max value of Pt/PPy-GOD(NapTS) electrode was approximately twice as high as that of Pt/PPy-GOD(pTSA) electrode as 25.4 and 14.2 mu A, respectively. Five commercial drinks were tested with enzyme electrodes and compared with results obtained spectrophotometrically using glucose kit. Results revealed that Pt/PPy-GODNapTS electrode exhibited better biosensor response.Öğe Glucose oxidase-polypyrrole electrodes synthesized in p-toluenesulfonic acid and sodium p-toluenesulfonate.(2011) Ozyilmaz, G.; Ozyilmaz, A.T.; Can, F.Amperometric glucose biosensors have been developed based on entrapment on platinum (Pt) electrode using cyclic voltammetry technique in glucose oxidase (GOD) and pyrrole containing p-toluenesulfonic acid (pTSA) or sodium p-toluenesulfonate (NapTS) as supporting electrolyte solutions. Both of electrolyte solutions were suitable media for the formation and deposition of polypyrrole-GOD (PPy-GOD) layers on Pt substrate. Pt/PPy-GOD electrodes brought about in different morphological properties as well as different electrochemical and biochemical response. The highest responses obtained in pTSA and NapTS electrolytes were observed at pH of 4.5 and 7.0 for Pt/PPy-GOD electrodes, respectively. While linearity was observed between 0.0-1.0 mM glucose substrate for both electrodes, I(max) value of Pt/PPy-GOD(NapTS) electrode was approximately twice as high as that of Pt/PPy-GOD(pTSA) electrode as 25.4 and 14.2 microA, respectively. Five commercial drinks were tested with enzyme electrodes and compared with results obtained spectrophotometrically using glucose kit. Results revealed that Pt/PPy-GOD(NapTS) electrode exhibited better biosensor response.Öğe Novel synthesis medium for poly(aniline-co-o-anisidine)(Elsevier Science Sa, 2006) Ozyilmaz, A. T.; Ozyilmaz, G.; Colak, N.Aqueous sodium oxalate (NaOX) solutions both without (1) and with (2) p-toluenesulfonic acid (p-TSA) were used to synthesize a poly (aniline-co-o-anisidine) (PANI-co-POA) film on mild steel (MS). Polarization of the substrate in p-TSA containing NaOX solution mixture led to the passivation of the surface mainly via the formation of an iron(II) oxalate layer. Copolymer coatings showed that p-TSA+NaOX solution mixture was a suitable medium for the deposition of a uniform, compact and strongly adherent PANI-co-POA coating on MS electrode. Similar coating was achieved when NaOX solution was used free of p-TSA. It was observed that addition of p-TSA in NaOX solution provided also an increase in electropolymerization rate. Evaluation of the anticorrosion performance of copolymer coatings in 3.5% NaCl solution was investigated by using AC impedance spectroscopy (EIS) technique and anodic polarization curves. Both copolymer coatings exhibited a significant physical barrier property against the attack of corrosive products on mild steel, in longer periods. (c) 2006 Elsevier B.V. All rights reserved.Öğe Phylogenetic Analysis and Characterization of Lipolytic Activity of Halophilic Archaeal Isolates(Maik Nauka/Interperiodica/Springer, 2012) Ozcan, B.; Ozyilmaz, G.; Cihan, A.; Cokmus, C.; Caliskan, M.Five isolates designated as B45, D83A, A206A, A85 and E49 found to possess lipolytic activities were taxonomically classified on the basis of their phylogenetic, phenotypic and chemotaxonomic characteristics. The isolates were determined to be gram-negative, catalase and oxidase positive, hydrolyzing Tween 80 and 60 but not starch, need 3.5-4 M NaCl for optimal growth and lack of anaerobic growth with arginine or DMSO. All isolates had the highest lipolytic activity at pH 8.5. Lipase and esterase activities increased with salt concentration up to 3-4.5 M NaCl, and decreased at 5 M NaCl. Esterase and lipase showed their maximal activities at 50-55 degrees C and 60-65 degrees C, respectively. The phylogenetic tree constructed by the neighbor-joining method indicated that the strain B45 and A85 were closely related to the members of genera Halovivax and Natrinema, respectively. The closest relative of the strain A206A and D83A were found to be Haloterrigena saccharevitans. The strain E49 displayed a more distant relationship to known strains.Öğe Phylogenetic analysis and characterization of lipolytic activity of halophilic archaeal isolates.(2012) Ozcan, B.; Ozyilmaz, G.; Cihan, A.; Cokmus, C.; Caliskan, M.Five isolates designated as B45, D83A, A206A, A85 and E49 and found to possess a activity were taxonomically classified on the basis of their phylogenetic, phenotypic and chemotaxonomic characteristics. The isolates were determined to be Gram-negative, catalase and oxidase positive, hydrolyzing Tween 80 and 60 but not starch, need 3.5-4 M NaCl for optimal growth and lack of anaerobic growth with arginine or DMSO. All isolates had the highest lipolytic activity at pH 8.5. Lipase and esterase activities increased with salt concentration up to 3-4.5 M NaCl, and decreased at 5 M NaCl. Esterase and lipase showed their maximal activities at 50-55 degrees C and 60-65 degrees C, respectively. The phylogenetic tree constructed by the neighbor-joining method indicated that the strain B45 and A85 were closely related to the members of genera Halovivax and Natrinema, respectively. The closest relative of the strain A206A and D83A were found to be Haloterrigena saccharevitans. The strain E49 displayed a more distant relationship to known strains.Öğe Simultaneous co-immobilization of glucose oxidase and catalase in their substrates(Pleiades Publishing Inc, 2007) Ozyilmaz, G.; Tukel, S. S.Glucose oxidase (GOD) and catalase (CAT) were simultaneously co-immobilized onto magnesium silicate (Florisil (R)) by covalent coupling. Glucose was added in immobilization mixture and hydrogen peroxide, which is the substrate of CAT, was produced in coupling mixture during immobilization time. Therefore, co-immobilization of GOD and CAT was carried out in the presence of both their substrates: glucose and hydrogen peroxide, respectively. The effect of glucose concentration in immobilization mixture on activities of GOD and CAT of co-immobilized samples were investigated. Maximum GOD and CAT activities were determined for samples co-immobilized in the presence of 15 and 20 mM glucose, respectively. Co-immobilization of GOD and CAT in the presence of their substrates highly improved the activity and reusability of both enzymes.Öğe Simultaneous co-immobilization of glucose oxidase and catalase in their substrates.(2007) Ozyilmaz, G.; Tukel, S.S.Glucose oxidase (GOD) and catalase (CAT) were simultaneously co-immobilized onto magnesium silicate (florisil) by covalent coupling. Glucose was added in immobilization mixture and hydrogen peroxide which is the substrate of CAT was produced in coupling mixture during immobilization time. Therefore, co-immobilization of GOD and CAT was carried out in presence of both their substrate: glucose and hydrogen peroxide, respectively. The effect of glucose concentration in immobilization mixture on activities of GOD and CAT of co-immobilized samples were investigated. Maximum GOD and CAT activities were determined for samples co-immobilized in presence of 15 and 20 mM glucose, respectively. Co-immobilization of GOD and CAT in presence of their substrates highly improved the activity and reusability of both enzymes.Öğe Synthesis and characterization of poly(aniline) and poly(o-anisidine) films in sulphamic acid solution and their anticorrosion properties(Elsevier Science Sa, 2010) Ozyilmaz, A. T.; Ozyilmaz, G.; Yigitoglu, O.Poly(o-anisidine) (POA) and polyaniline (PANI) coatings were synthesized on platinum (Pt) surface and stainless steel(SS)in monomer containing 0.50 M sulphamic acid (SA) solution by means of cyclic voltammetry (CV) technique. Meanwhile, poly(o-anisidine) film was also deposited with a different scan rate on SS electrode. The behaviour of PANI and POA films obtained on stainless steel examined by CV was different from the one obtained for PAN] and POA on Pt electrode. The corrosion performances of PANI and POA coatings in 3.5% NaCl solution were investigated with anodic polarization technique and electrochemical impedance spectroscopy (EIS). EIS measurements verified the effect of monomers and that of scan rate on corrosion inhibition of coatings on SS electrode. The results showed that POA film synthesized at low scan rate exhibited an effective anticorrosive property on SS electrode. POA synthesized at low scan rate and PANI coatings provided a remarkable anodic protection to SS substrate for longer exposure time than the one observed for POA coating produced at high scan rate as well as that of bare SS electrode. (C) 2009 Elsevier BY. All rights reserved.
