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Öğe 1,10-Phenanthroline-5,6-dione and 9,10-phenanthrenequinone as redox mediators for amperometric glucose biosensors(SPRINGER, 2014) Zor, Erhan; Oztekin, Yasemin; Mikoliunaite, Lina; Voronovic, Jaroslav; Ramanaviciene, Almira; Anusevicius, Zilvinas; Bingol, HalukIn this study, two ortho-quinoidal compounds, 1,10-phenanthroline-5,6-dione (PD) and 9,10-phenanthrenequinone (PQ), were examined as electron transfer mediators suitable for amperometric glucose biosensors. The dependences of the electrochemical responses of PD- and PQ-based amperometric glucose biosensors on varied concentrations of glucose were investigated under aerobic and anaerobic conditions. The PD-modified graphite rod (GR) electrode revealed a current response seven times higher than that of the PQ-modified GR electrode. The reactivity indices of ortho-quinoidals assessed by means of B3LYP functional method applying 6-311G(D) basis set showed that the electron-accepting potency for PD was markedly higher as compared with that of PQ. Compared to PQ, considerably higher reactivity of PD has been defined in the reactions with NADP(+)-ferredoxin reductase (FNR, EC 1.18.1.2) as a model single-electron transfer FAD-dependent enzyme, which provided an additional evidence for PD as a more efficient mediator compared to PQ. This study illustrates that PD can be applied as a redox mediator for glucose oxidase and it could be more suitable for a reagent-less biosensor design than PQ.Öğe Catalytic degradation of organic dye using reduced graphene oxide-polyoxometalate nanocomposite(ELSEVIER SCIENCE SA, 2017) Ucar, Asuman; Findik, Mukerrem; Gubbuk, I. Hilal; Kocak, Nuriye; Bingol, HalukSilicotungstic acid (SiW) decorated reduced graphene oxide (rGO) nanocomposite (rGO-SiW) has been prepared and evaluated as a heterogeneous nanocatalyst for the degradation reactions of methylene blue (MB) and rhodamine B (RhB). The structural and morphological properties of rGO-SiW nanocomposite were investigated by various techniques such as Fourier transform infrared spectroscopy (FT-IR), Raman spectroscopy, X-ray diffraction (XRD), Atomic force microscopy (AFM) and Scanning electron microscope (SEM), which revealed the homogeneous and noncovalent anchoring of SiW nanoparticles on rGO sheets. The catalytic activity of rGO-SiW nanocomposite on the degradations of MB and RhB has been monitored using UV-visible absorption spectrometry in the presence of NaBH4 as the reducing agent at room temperature in water. The reduction reactions followed pseudo-first order kinetics and degradation were achieved in 34 min for MB and 81 min for RhB using rGO-SiW as catalysts. (C) 2017 Elsevier B.V. All rights reserved.Öğe Evaluation of 1,10-phenanthroline-5,6-dione as redox mediator for glucose oxidase(MAIK NAUKA/INTERPERIODICA/SPRINGER, 2016) Zor, Erhan; Oztekin, Yasemin; Ramanaviciene, Almira; Anusevicius, Zilvinas; Voronovic, Jaroslav; Bingol, Haluk; Barauskas-Memenas, DanaA low-cost and simply fabricated amperometric glucose biosensor based on glucose oxidase (GOx) and 1,10-phenanthroline-5,6-dione (PD) modified graphite rod electrode was developed. The electrode exhibited good electrocatalytic activity with a well-defined hyperbolic dependence of amperometric signal upon glucose concentration in the presence and in the absence of oxygen. The electrode showed a good reproducibility and repeatability with relative standard deviation of less than 3 and 5%, respectively. The interaction of GOx with PD mediator was confirmed by means of UV?Vis absorbance spectroscopy.Öğe Facilitated Proton Transfer by a Novel 2-Aminothiazole Derivative Across the Water/1,2-Dichloroethane Interface(SPRINGER/PLENUM PUBLISHERS, 2011) Bingol, Haluk; Coskun, AhmetThe behavior of proton transfer facilitated by a novel thiazole derivative, N-methyl-4-(4-phenoxyphenyl)thiazol-2-amine (MPPT), across the water/1,2-dichloroethane (1,2-DCE) interface was investigated electrochemically. The ionic partition diagram for MPPT was obtained from interpretation of the cyclic voltammograms. The apparent partition coefficient of MPPT was evaluated by the shaking-flask method under experimental conditions, while that for the protonated form of MPPT was calculated from its transfer potential obtained from the ionic partition diagram. It was suggested that the mechanism for transfer of MPPT across the water/1,2-DCE) interface depends on the pH of the aqueous phase. The parameters of the facilitated proton transfer across the water/1,2-DCE interface were evaluated as a quantitative measure of its lipophilicity.Öğe Fluorogenic ferrocenyl Schiff base for Zn2+ and Cd2+ detection(SPRINGER, 2017) Findik, Mukerrem; Ucar, Asuman; Bingol, Haluk; Guler, Ersin; Ozcan, EmineA novel sensor based on acetylferrocene-containing Schiff base (ASB) was synthesized by reaction of alpha-chloroacetylferrocene and N-(salicylidene)-l-valinmethylester. The structure of the compound was characterized by using elemental analysis and Fourier-transform infrared (FT-IR), H-1 nuclear magnetic resonance (NMR), and C-13 NMR spectroscopy. Its metal-cation-sensing properties were investigated spectrofluorometrically. ASB served as selective chemosensor for Zn2+ and Cd2+ towards alkali, alkaline-earth, and various heavy-metal ions. It showed significant fluorescence enhancement for Zn2+ and Cd2+ ions, stemming from C=N isomerization and chelation-enhanced fluorescence. The binding modes of the complexes were determined to have 1:1 complexation stoichiometry, and the binding constants were calculated as (6.93 +/- 0.25) x 10(6) M-1 for ASB center dot Zn (2+) and (7.49 +/- 0.18) x 10(5) M-1 for ASB center dot Cd (2+) using the nonlinear curve-fitting method.Öğe Organometallic chiral Schiff base for enantio-selective fluorescent recognition of methionine(SPRINGER INTERNATIONAL PUBLISHING AG, 2017) Ucar, Asuman; Findik, Mukerrem; Bingol, Haluk; Guler, Ersin; Ozcan, EmineHerein, the synthesis and characterization of a novel chiral Schiff bases derived from ferrocene, coded as 3, have been reported. The sensing behavior of the synthesized compound has been examined towards the enantiomers of some amino acids (methionine, alanine, serine, histidine, and threonine) by spectrofluorimetric method. The fluorescence response of compound 3 showed noticeable enhancement upon addition of d-methionine compared to l-methionine and kept nearly linear correlation with the concentration of d-methionine. The value of enantiomeric fluorescence difference ratio (ef) has been determined to be 1.54 when d - and l- methionine amount is 100 times more than compound 3. The results showed that the compound 3 can be used as a sensor for enantio-selective recognition of d-methionine.Öğe Preparation of a novel PSf membrane containing rGO/PTh and its physical properties and membrane performance(ROYAL SOC CHEMISTRY, 2015) Saf, Ahmet Ozgur; Akin, Ilker; Zor, Erhan; Bingol, HalukRecent advances in the fabrication of nanostructures such as graphene-related materials have received a lot of attention in membrane technology for the future of water supplies. Herein, we report the synthesis of a reduced graphene oxide/polythiophene (rGO/PTh) composite material using an in situ enzymatic polymerization reaction, which is an eco-friendly and a simple way to construct a nanocomposite material. Polysulfone (PSf) mixed matrix composite membranes containing rGO and rGO/PTh were prepared via a phase inversion method. The morphology of the membranes was evaluated by various characterization methods, including SEM, AFM, contact angle and porosity measurements. The performance and antifouling properties of the membranes were examined in detail. The PSf-rGO/PTh membrane showed a significant improvement in water flux permeability due to the enhancement of hydrophilicity and porosity. Moreover, the PSf-rGO/PTh membrane exhibited an approximately 10 times higher improved water flux than that of the rGO membrane as the pressure was increased. The fouling resistance ratio (FRR) and antifouling properties of the membranes were tested using two different protein solutions: bovine serum albumin (BSA) and cytochrome c (Ctc). The antifouling and FRR properties of the PSf-rGO/PTh membrane decreased due to not only the interactions between the functional groups on the membrane surface and fouling materials, but also the morphological properties of the membrane.Öğe Spectrophotometric and electrochemical behavior of a novel azocalix[4]arene derivative as a highly selective chromogenic chemosensor for Cr+3(PERGAMON-ELSEVIER SCIENCE LTD, 2011) Bingol, Haluk; Kocabas, Erdal; Zor, Erhan; Coskun, AhmetIn this study, a novel azocalix[4]arene derivative, 5,11,17-tris[(1-naphtyl)azo]-25,26,27,28-tetrahydroxycalix[4]arene (NAC4) bearing napthyl groups on the upper rim was synthesized. Its complexation behavior for alkali, alkaline-earth and various heavy metal ions (Li+, Na+, K+, Rb+, Cs+, Mg2+, Ca2+, Sr2+, Ba2+, Pb2+, Hg2+, Ni2+, Cd2+, Cu2+, Zn2+, Co2+, Fe2+, Cr3+, Ag+) was investigated by spectroscopic and voltammetric methods. This chemosensor exhibits decreased absorbance in the presence of Hg2+ and a unique absorbance quenching effect only for Cr3+. In addition, a new absorption band centered at 565 nm with the formation of the 1:1 host-guest complex (Cr3+-NAC4) was observed in the case of Cr3+, leading to an obvious color change from light orange to dark lilac. In voltammetric experiments, Cr3+ ions decreased voltammetric peaks of NAC4, whereas no significant changes occurred in the presence of the other metal ions. The Benesi-Hildebrand method was used to determine a logarithmic value of 3.76 for the association constant of the complex between Cr3+ and NAC4. (C) 2010 Elsevier Ltd. All rights reserved.Öğe Spectrophotometric and voltammetric characterization of a novel selective electroactive chemosensor for Mg2+(VERSITA, 2013) Zor, Erhan; Saf, Ahmet Ozgur; Bingol, HalukA novel azocalix[4]arene derivative, 5,11,17,23-tetrakis[(acetophenone)azo]-25,26,27,28-tetrahydroxycalix[4]arene (APC4), containing acetophenone azo groups at the upper rim was synthesized as a chemosensor. Its binding and sensing properties with alkali and alkaline earth metal ions (Li+, Na+, K+, Rb+, Cs+, Mg2+, Ca2+, Sr2+, Ba2+) were investigated by UV-vis spectrophotometric and voltammetric techniques. The stoichiometric ratio and the association constant were determined spectrophotometrically as 1:1 and (1.94 +/- 0.31)x10(5) L mol(-1) for the complex between Mg2+ and the chemosensor, respectively. Moreover, it was shown that the interaction between Mg2+ and the APC4 occurred by means of the phenol groups at the lower rim by voltammetric methods. The results of spectrophotometric and voltammetric experiments showed that the chromogenic chemosensor has high selectivity towards Mg2+ among the other used metal ions, especially the interfering Ca2+ ion.Öğe Synthesis of a Novel Thiadiazine Derivative and Electrochemical Properties for Pb2+ Transfer across Water/1,2-Dichloroethane Interface(PEKING UNIV PRESS, 2011) Baslak, Canan; Bingol, Haluk; Coskun, Ahmet; Atalay, TevfikThe transfer of Pb2+ facilitated by interfacial complexation with 5-(4-phenoxyphenyl)-6H-1,3,4-thiadiazin-2-amine (PPTA) at the polarized water/1,2-dicholoroethane (1,2-DCE) interface was investigated by cyclic voltammetry. We synthesized the thiadiazine derivative, PPTA, firstly. The transfer was performed at different metal concentrations and scan rates, and the obtained voltammetric transfer peaks toward Pb2+ ion over other divalent cations (Zn2+, Co2+, Ni2+, Cd2+, Hg2+, and Cu2+) were reversible. The dependence of the half-wave potentials of the Pb2+ ion on the concentration of PPTA in the organic phase indicates that the ion transfer is facilitated by the formation of 1:2 (metal: ligand) complex in the organic phase with the association constant (Ig beta(2)) of (17.1 +/- 0.2).
