Yazar "Gulce, Handan" seçeneğine göre listele

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    Amperometric biosensors based on deposition of gold and platinum nanoparticles on polyvinylferrocene modified electrode for xanthine detection
    (ELSEVIER, 2011) Bas, Salih Zeki; Gulce, Handan; Yildiz, Salih; Gulce, Ahmet
    In this study, new xanthine biosensors, XO/Au/PVF/Pt and XO/Pt/PVF/Pt, based on electroless deposition of gold(Au) and platinum(Pt) nanoparticles on polyvinylferrocene(PVF) coated Pt electrode for detection of xanthine were presented. The amperometric responses of the enzyme electrodes were measured at the constant potential, which was due to the electrooxidation of enzymatically produced H2O2. Compared with XO/PVF/Pt electrode, XO/Au/PVF/Pt and XO/Pt/PVF/Pt exhibited excellent electrocatalytic activity towards the oxidation of the analyte. Effect of Au and Pt nanoparticles was investigated by monitoring the response currents at the different deposition times and the different concentrations of KAuCl4 and PtBr2. Under the optimal conditions, the calibration curves of XO/Au/PVF/Pt and XO/Pt/PVF/Pt were obtained over the range of 2.5 x 10(-3) to 0.56 mM and 2.0 x 10(-3) to 0.66 mM, respectively. The detection limits were 7.5 x 10(-4) mM for XO/Au/PVF/Pt and 6.0 x 10(-4) mM for XO/Pt/PVF/Pt. The effects of interferents, the operational and the storage stabilities of the biosensors and the applicabilities of the proposed biosensors to the drug samples analysis were also evaluated. (C) 2011 Elsevier B.V. All rights reserved.
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    Amperometric xanthine biosensors based on electrodeposition of platinum on polyvinylferrocenium coated Pt electrode
    (ELSEVIER, 2011) Bas, Salih Zeld; Gulce, Handan; Yildiz, Salih
    Novel xanthine biosensors were successfully fabricated by immobilizing xanthine oxidase on polyvinylferrocenium perchlorate matrix (PVF+ClO4-) and platinum electrodeposited polyvinylferrocenium perchlorate matrix. PVF+ClO4- film was coated on Pt electrode at +0.7 V vs. Ag/AgCl by electrooxidation of polyvinylferrocene (PVF). Platinum nanoparticles were deposited on PVF+ClO4- electrode by electrochemical deposition in 2.0 mM H2PtCl6 solution at -0.2 V. Xanthine oxidase was incorporated into the polymer matrix via ion exchange process by immersing modified Pt electrodes in the enzyme solution. The amperometric responses of the biosensors were measured via monitoring oxidation current of hydrogen peroxide at +0.5 V. Under the optimal conditions, the linear ranges of xanthine detection were determined as 1.73 x 10(-3)-1.74 mM for PVF+XO- and 0.43 x 10(-3)-2.84 mM for PVF+XO-/Pt. The detection limits of xanthine were 5.20 x 10(-4) mM for PVF+XO- and 1.30 x 10(-4) mM for PVF+XO-/Pt. Moreover, the effects of applied potential, electrodeposition potential, H2PtCl6 concentration, amount of electrodeposited Pt nanoparticles, thickness of polymeric film, temperature, immobilization time, xanthine and xanthine oxidase concentrations on the response currents of the biosensors were investigated in detail. The effects of interferents, the operational and storage stabilities of biosensors and the applicabilities to drug samples of the biosensors analysis were also evaluated. (C) 2011 Elsevier B.V. All rights reserved.
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    Efficient photocatalytic decolorization of some textile dyes using Fe ions doped polyaniline film on ITO coated glass substrate
    (ELSEVIER, 2013) Haspulat, Bircan; Gulce, Ahmet; Gulce, Handan
    In this study, the photocatalytic decolorization of four commercial textile dyes with different structures has been investigated using electrochemically synthesized polyaniline and Fe ions doped polyaniline on ITO coated glass substrate as photocatalyst in aqueous solution under UV irradiation for the first time. Scanning electron microscopy, atomic force microscopy, FT-IR spectra, UV-vis spectroscopy measurements were used to characterize the electrochemically synthesized polymer film photocatalyst. Film hydrophilicity was assessed from contact angle measurements. The results show that both of the polymer films exhibit good photocatalytic performance. Surprisingly, it was determined that by using Fe(II) ions during polymerization, it is possible to modify the surface roughness and wettability of the produced polyaniline films which favors their photocatalytic activity in water-based solutions. All four of the used dyes (methylene blue, malachite green, methyl orange and methyl red) were completely decolorizated in 90 min of irradiation under UV light by using Fe ions doped polyaniline at the dye concentration of 1.5 x 10(-5) M, while the decolorization of those dyes were between 43% and 83% by using polyaniline as photocatalyst. Hence, it may be a viable technique for the safe disposal of textile wastewater into waste streams. (C) 2013 Elsevier B.V. All rights reserved.
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    Glucose biosensor based on immobilization of glucose oxidase in electropolymerized poly(o-phenylenediamine) film on platinum nanoparticles-polyvinylferrocenium modified electrode
    (PERGAMON-ELSEVIER SCIENCE LTD, 2014) Turkmen, Esra; Bas, Salih Zeki; Gulce, Handan; Yildiz, Salih
    A new biosensor based on immobilization of glucose oxidase (Gox) using enzyme solution containing o-phenylenediamine(oPD) on platinum nanoparticles (PtNPs) electrodeposited polyvinylferrocenium perchlorate matrix (PVF+ClO4-) was fabricated for the bioelectrochemical determination of glucose. Firstly, PVF+ClO4- film was electroprecipitated on Pt electrode by electrooxidation of polyvinylferrocene, and then PtNPs were electrodeposited on PVF+ClO4-/Pt. Finally, Gox was immobilized simultaneously with the electropolymerization of oPD on PtNPs/PVF+ClO4-/Pt. The biosensor showed excellent anti-interference ability to ascorbic acid and uric acid due to the permselectivity of PoPD in the structure of the proposed biosensor. The linear range of Gox-PoPD/PtNPs/PVF+ClO4-/Pt was from 0.06 mM to 9.64 mM with a sensitivity of 17.40 mu A mM(-1) cm(-2) and a detection limit of 0.018 mM. The effects of applied potential, PVF+ClO4- film thickness, oPD concentration, Gox concentration, electropolymerization time and temperature on the response current of the biosensor were investigated in detail. The electrocatalytic effect of PtNPs as well as repeatability, reproducibility and stability of the biosensor were also studied. PtNPs modified PVF+ClO4-/Pt exhibited excellent electrocatalytic activity to the electrooxidation of H2O2. In addition, the biosensor was successfully applied for the determination of glucose concentration in human blood serum samples. (C) 2014 Elsevier Ltd. All rights reserved.
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    Hypoxanthine Biosensor Based on Immobilization of Xanthine Oxidase on Modified Pt Electrode and Its Application for Fish Meat
    (TAYLOR & FRANCIS AS, 2014) Bas, Salih Zeki; Gulce, Handan; Yildiz, Salih
    In this study, hypoxanthine biosensor based on immobilization of xanthine oxidase on polyvinylferrocenium perchlorate matrix coated Pt electrode for detection of hypoxanthine was presented. The steady-state background current of the biosensor was measured at+0.5V, which was due to the electrooxidation of enzymatically produced H2O2. The biosensor exhibited a linear range from 2.15x10(-3)mM to 1.03mM (r=0.9963) with a detection limit of 6.5x10(-4)mM (S/N=3) for the detection of hypoxanthine. The storage stability of the biosensor, the effect of interference by uric acid, and the applicability to fish sample of the biosensor analysis were also evaluated.
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    Nafion-Graphene Composite Film Modified Glassy Carbon Electrode for Voltammetric Determination of p-Aminophenol
    (PLEIADES PUBLISHING INC, 2014) Filik, Hayati; Cetintas, Gamze; Koc, Serkan Naci; Gulce, Handan; Boz, Ismail
    A Nafion-graphene (Nafion-GR) nanocomposite film modified glassy carbon electrode was fabricated by a simple drop -casting method, and used in the electrochemical detection of p-aminophenol (4-AP). Owing to the large surface area, good conductivity of GR and good affinity of Nafion, the sensor exhibited excellent electrocatalytic activity for the oxidation of 4-AP. The electrochemical behaviors of 4-AP on Nafion/GR film modified glassy carbon electrodes were investigated by cyclic voltammetry and differential pulse voltammetry. A calibration curve is constructed in the same matrix, urine, as the unknown samples to be analyzed. The Nafion-GR film modified electrode was linearly dependent on the 4-AP concentration and the linear analytical curve was obtained in the ranges of 0.5-200-M with differential pulse voltammetry (DPV) and the detection limit was 0.051-M. The Nafion-graphene nanocomposite modified electrode exhibited good reusability than pure graphene modified GCE. This procedure can be used for the determi- nation of p-aminophenol in the presence of its degradation products and paracetamol. Finally, the proposed method was successfully used to determine p-aminophenol in local tap water samples in urine samples and pharmaceutical preparations.
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    Novel Ni/Polypyrrole and Cu/Polypyrrole composites prepared in the presence of different acids: Synthesis and investigation of thermal stability
    (WILEY, 2007) Sen, Songul; Gok, Aysegul; Gulce, Handan
    We report the synthesis and characterization of new organic/inorganic hybrid materials constituted of Ni(0) and Cu(0) nanoparticles and polypyrrole (PPy). Copper and nickel nanoclusters were synthesized by a chemical reduction of aqueous metal salt solutions by sodium borohydride. PPy/Ni(0) and PPy/Cu(0) composites were obtained in the presence of two different acids H3BO3, CH3COOH), by polymerizing pyrrole-Ni and pyrrole-Cu particles by using iron (III) chloride. The composites have been characterized by scanning electron microscopy (SEM), energy dispersive spectrometer (EDS), thermogravimetric analysis (TGA), Fourier transform infrared spectroscopy (FTIR), and magnetic susceptibility techniques. Conductivity measurements of samples were taken using four-probe devices. The PPy/Ni(0) and PPy/Cu(0) nanocomposites doped with different acids exhibited higher conductivity values than those of homopolymers. Among all samples, Ni/PPy-H3BO3 has the highest conductivity (1.42 S cm(-1)). Homopolymers and composites showed a stable and increasing conductivity with increasing temperature, except Ni(0). We observed that from TGA analysis of polymers, metal composites of PPy synthesized in two different media are more stable than those of PPy-CH3COOH and PPy-H3BO3. The magnetic susceptibility values of homopolymers and Cu are negative, whereas the other samples are positive.
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    Polyvinylferrocenium based platinum electrodeposited amperometric biosensors for lysine detection
    (ELSEVIER SCIENCE SA, 2013) Sahin, Ozlem Gokdogan; Gulce, Handan; Gulce, Ahmet
    Two amperometric biosensors based on polyvinylferrocenium (PVF+) and platinum deposited PVF+ were constructed for lysine detection. The method for modification of electrodes relied on the electrooxidation of polyvinylferrocene in methylene chloride containing tetrabutylammonium perchlorate (TBAP) at +0.70 V and electrodeposition of platinum particles on the surface of PVF+ClO4- at -0.15 V vs. Ag/AgCl. Lysine oxidase (LyOx) enzyme was immobilized by ion exchange process into modified electrodes. The response of the resulted PVF(+)LyOx(-) and PVF(+)LyOx(-)/Pt biosensors determined by oxidation of enzymatically produced H2O2 at 0.60 V vs. Ag/AgCl. The influence of experimental conditions such as applied potential, pH, temperature on the biosensor responses were examined and analytical performance characteristics of the biosensors were determined. The experimental results of two biosensors compared with each other. The results showed that PVF(+)LyOx(-)/Pt biosensor had a linear range up to 3.0 mM whereas for PVF(+)LyOx(-) biosensor that range was linear up to 1.3 mM. The detection limits of PVF(+)LyOx(-)/Pt and PVF(+)LyOx(-) biosensors were determined to be about 6.5 x 10(-4) and 5.0 x 10(-4) mM, respectively. The response time of sensors was less than 30 s. The anti-interference ability and long-term stability of the biosensors were studied. The proposed biosensors were also used to determine lysine in pharmaceutical samples. (C) 2012 Elsevier B.V. All rights reserved.
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    Preparation of a New Polyaniline/CdO Nanocomposite and Investigation of Its Photocatalytic Activity: Comparative Study under UV Light and Natural Sunlight Irradiation
    (AMER CHEMICAL SOC, 2013) Gulce, Handan; Eskizeybek, Volkan; Haspulat, Bircan; Sari, Fahriye; Gulce, Ahmet; Avci, Ahmet
    Polyaniline (PANI)/CdO nanocomposite was prepared for the first time in aqueous diethylene glycol solution medium, by chemical oxidative polymerization, and its photocatalytical activity was studied. Optical analysis of the new PANI/CdO nanocomposite revealed that electron densities and bond energies of the PANI homopolymer decreased after modifying with CdO nanoparticles, due to interactions between PANI chains and CdO nanoparticles. The prepared PANI/CdO nanocomposite exhibits excellent photocatalytic activity under both UV light and natural sunlight irradiation. The photocatalytic decolorization rate was increased up to 7 times after CdO addition, compared to the decolorization rate of PANI homopolymer under UV light irradiation. During the photocatalytic activity investigations, methylene blue and malachite green dyes were photocatalytically decolorized under natural sunlight irradiation with 99% efficiency by the use of 0.4 mg/mL PANI/CdO nanocomposite as photocatalyst. Furthermore, the PANI/CdO photocatalyst retains its efficiency with slight decreases upon being reused up to five times.
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    Synthesis and characterization of polyvinylferrocene/polypyrrole composites
    (TAYLOR & FRANCIS INC, 2008) Sen, Songuel; Gok, Aysegul Uygun; Gulce, Handan; Aldissi, Matt
    Conducting polymer composites of polyvinylferrocene and polypyrrole (PVF/PPy) were synthesized chemically by the in situ polymerization of pyrrole in the presence of PVF using FeCl3 as oxidant. Acetic (CH3COOH) and boric (H3BO3) acids were used as the synthesis medium. Effects of the synthesis medium on the properties of the PVF/PPy composite were investigated. The PVF/PPy composites and homopolymers were characterized by fourier transform infrared spectroscopy (FTIR), thermogravimetric analysis (TGA), scanning electron microscopy (SEM), energy dispersive spectroscopy (EDS) and magnetic susceptibility techniques. Conductivity measurements were performed using the four-probe technique. We found that the conductivities of PVF/PPy-H3BO3 (1.19 S cm(-1)) and PVF/PPy-CH3COOH (4.510-1 S cm(-1)) increased relative to those of the homopolymers of PPy-H3BO3 (2.110-2 S cm(-1)) and PPy-CH3COOH (1.210-2 S cm(-1)) due to the interaction of PVF with the pyrrole moiety. The stability of all homopolymers and composites were investigated by thermogravimetric analysis and by conductivity measurements during heating-cooling cycles. There was a small drop in conductivity caused by the annealing of PVF/PPy composites at 70 degrees C. The conductivity of all samples increased with temperature and exhibited stable electrical behavior with increasing temperature. TGA analysis of samples showed that the composites were more stable than the homopolymers or PVF separately. The magnetic susceptibility values of samples were negative, except for PVF/PPy-H3BO3. Morphology changes of the composites investigated by scanning electron microscopy (SEM), attributed to synthesis conditions, have a significant effect on their conductivity.
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    ZnO-TiO2 nanocomposites formed under submerged DC arc discharge: preparation, characterization and photocatalytic properties
    (SPRINGER, 2014) Avci, Ahmet; Eskizeybek, Volkan; Gulce, Handan; Haspulat, Bircan; Sahin, Omer Sinan
    A rutile TiO2 (alpha-TiO2) and hexagonal wurtzite ZnO nanocomposite was directly and synchronously synthesized via arc discharge method submerged in de-ionized water. In correlation with the detailed characterization of the morphology, and crystalline structure of the prepared ZnO-TiO2 nanocomposites, the UV-visible and photoluminescence properties were studied. X-ray diffraction and transmission electron microscopy investigations revealed the co-existence of alpha-TiO2 and hexagonal wurtzite ZnO phases with the ZnO and alpha-TiO2 nanoparticles are in nanorod and nanospheres morphologies, respectively. The diameters of the synthesized nanocomposite particles are in the range of 5-70 nm. Interestingly, the as-prepared ZnO-TiO2 nanocomposite shows better photocatalytic activity for photodegradation of the methylene blue dye than both of pure ZnO and TiO2 nanocatalyts. This work would explore feasible routes to synthesize efficient metal or/and metal oxide nanocomposites for degrading organic pollutants, gas sensing or other related applications.