Yazar "Solak, Ali Osman" seçeneğine göre listele

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    2-BENZO[C]CINNOLINE AND 2-BENZO[C]CINNOLINE 6-OXIDE MODIFIED GLASSY CARBON ELECTRODES: ELECTROCATALYTIC REDUCTION OF DIOXYGEN IN AQUEOUS MEDIA
    (Taylor & Francis Inc, 2011) Isbir-Turan, Aybuke A.; Ustundag, Zafer; Kilic, Emine; Guzel, Remziye; Uckan, Oznur; Solak, Ali Osman
    Benzo[c]cinnoline (BCC) molecules were electrochemically grafted onto a glassy carbon (GC) surface in nonaqueous media, and the modified surface was characterized using cyclic voltammetry (CV) with redox probes. Blockage of the electron transfer on the modified surface was observed using redox probes. Electrocatalytic effect of 2BCC modified GC (2BCC-GC) electrode surface towards to the electrochemical reduction of dioxygen was also investigated. A mechanistic scheme for the electrochemical catalysis was proposed. To clarify the mechanism of the dioxygen reduction, a less basic film of 2-benzo[c]cinnoline 6-oxide (2BCCNO) molecules was also prepared at the glassy carbon surface. The effect of electrochemical catalysis of dioxygen reduction at the 2BCC-GC surface was compared to that at the 2BCCNO-GC surface.
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    Analysis of the Nano-Surface of a Modified Glassy Carbon Electrode by Pseudo Phase Plane Method
    (Amer Scientific Publishers, 2011) Tenreiro Machado, J. A.; Baleanu, Dumitru; Dinc, Erdal; Solak, Ali Osman; Eksi, Haslet; Guzel, Remziye
    This paper presents the Pseudo phase plane (PPP) method for detecting the existence of a nanofilm on the nitroazobenzene-modified glassy carbon electrode (NAB-GC) system. This modified electrode systems and nitroazobenze-nanofilnn were prepared by the electrochemical reduction of diazonium salt of NAB at the glassy carbon electrodes (GCE) in nonaqueous media. The IR spectra of the bare glassy carbon electrodes (GCE), the NAB-GC electrode system and the organic NAB film were recorded. The IR data of the bare GC, NAB-GC and NAB film were categorized into five series consisting of FILM1, GC-NAB1, GC1; FILM2, GC-NAB2, GC2; FILM3, GC-NAB3, GC3 and FILM4, GC-NAB4, GC4 respectively. The PPP approach was applied to each group of the data of unmodified and modified electrode systems with nanofilm. The results provided by PPP method show the existence of the NAB film on the modified GC electrode.
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    Determination of Acetaminophen in Commercial Formulations Using Silver Nanostructured Aniline Modified Pencil Graphite Electrode
    (Electrochemical Soc Inc, 2013) Guzel, Remziye; Eksi, Haslet; Dinc, Erdal; Solak, Ali Osman
    A nanostructured silver-aniline modified pencil electrode obtained by applying experimental design and optimization was developed for the differential pulse stripping voltammetric quantification of acetaminophen in the pharmaceutical products, tablet and syrup. The electrode development process was performed by the modification of PGE with aniline using CV procedure and the reduction of silver nanoparticle on the polyaniline modified PGE. As a result, a new electrode system consisting of a nanostructured silver-polyaniline modified pencil graphite electrode (AgNS-PA-PGE) was obtained to reach a well-defined and higher peak current for the analysis of the related drug. The calibration curve was found linear in the range of 5 x 10(-8)-8 x 10(-7) M for acetaminophen. The validity and applicability of the proposed voltammetric method was tested by analyzing independent validation samples. It was observed that the proposed voltammetric approach for the real tablet and syrup samples gave successful analysis results. (C) 2013 The Electrochemical Society. All rights reserved.
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    Fabrication of an electrochemical E. coli biosensor in biowells using bimetallic nanoparticle-labelled antibodies
    (Wiley-V C H Verlag Gmbh, 2015) Ekşi, Haslet; Güzel, Remziye; Güven, Burcu; Boyacı, İsmail Hakkı; Solak, Ali Osman; 0000-0003-1333-060X
    An electrochemical biosensor was developed for the determination of Escherichia coli (E. coli) in water. For this purpose, silver-gold core-shell (Ag@Au) bioconjugates and anti-E. coli modified PS-microwells were designed in a sandwich-type format in order to obtain higher sensitivity and selectivity. Ag@Au bimetallic nanoparticles were synthesized by co-reduction method. The core-shell formation was analyzed by using UV-Vis spectroscopy and transmission electron microscopy. Biotin labeled anti-E. coli antibodies were coupled with Ag@Au nanoparticles to form bioconjugates. The electrochemical immunosensor was prepared by immobilizing anti-E. coli on polystyrene (PS)-microwells via chemical bonding. These modified microwells were identified with X-ray photoelectron spectroscopy and surface enhanced Raman spectroscopy. E. coli was sandwiched between Ag@Au bioconjugates and anti-E. coli on PS-microwells at different concentrations. The relationship between the E. coli concentration and stripping current of gold ions (Au3+) were investigated by square wave anodic stripping voltammetry at pencil graphite electrode. The proposed method can provide some advantages such as lower detection limit and shorter detection time. The electrochemical response for the immunosensor was linear with the concentration of the E. coli in the range of 10(1) and 10(5) cfu/mL with a limit of detection 3 cfu/mL. The procedure maintains good sensitivity and repeatability and also offers utility in the fields of environmental monitoring and clinical diagnosis.
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    Factor Analysis for the Characterization of the Nano-Surface of the Nitroazobenzene-Modified Glassy Carbon Electrode
    (Amer Scientific Publishers, 2012) Dinc, Erdal; Baleanu, Dumitru; Solak, Ali Osman; Eksi, Haslet; Guzel, Remziye
    Factor analysis with orthogonal varimax rotation was applied to determine the existence of a nano-structure on the nitroazobenze-modified glassy carbon electrode (NAB-GC) system. The NAB-GC electrode systems and benzoic acid-nanofilm (NAB-FILM) were obtained by using the electrochemical surface modification experiments. The IR spectra of the bare glassy carbon electrodes (GC), the NAB-GC electrode system and NAB-FILM were recorded. The IR data of the bare GC, BA-GC and BA-FILM were categorized into five series consisting of FILM1, GC-NAB1, GC1; FILM2, GC-NAB2, GC2; FILM3, GC-NAB3, GC3; FILM4, GC-NAB4, GC4; FILM5, GC-NAB5, GC5, respectively. The factor loadings were extracted by making use of the factor analysis approach applied to each group. The orthogonal varimax rotation technique was used to obtain the rotated factor loadings corresponding to the first two factors. After the estimation of the relationship among and within groups, the results predict the existence of the NAB-FILM on the NAB modified glassy carbon electrodes.
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    A new approach to the characterization of the nano-surface structure by using factor analysis
    (Elsevier, 2012) Dinc, Erdal; Baleanu, Dumitru; Solak, Ali Osman; Eksi, Haslet; Guzel, Remziye
    The study provides a new approach to explore the existence of a nanostructure on the benzoic acid-modified glassy carbon electrode (BA-GC) system by applying factor analysis with varimax rotation of factors. The infrared spectra (IR) spectra of the bare glassy carbon electrodes (GC) and the BA-GC electrode systems with benzoic acid-nanofilm (BA-FILM) were obtained by using 10 different surface modification experiments. The IR data of the bare GC, BA-GC and BA-FILM were categorized into three series corresponding to the GC, BA-GC and BA-FILM. The factor analysis method was separately applied to each group to extract the factor loadings. By making use of these loadings, the rotated factor loadings corresponding to the first two factors were computed to estimate the relationship among and within groups. The results provided by the factor analysis method indicate the existence of the BA-FILM on the BA modified glassy carbon electrode. (C) 2011 Elsevier B.V. All rights reserved.
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    New Voltammetric Approach to the Quantitation of Paracetamol in Tablets and Syrup using Chemometric Optimization Technique
    (Pleiades Publishing Inc, 2019) Guzel, Remziye; Eksi, Haslet; Dinc, Erdal; Solak, Ali Osman
    A new voltammetric approach was developed for the determination of paracetamol in tablet and syrup samples using chemometric optimization. The method is based on the use of the gold nanoparticles-polyaniline (AuNPs-PA) modified pencil graphite electrode (PGE). Electrode system was fabricated by using the electrochemical reduction of gold on aniline modified pencil electrode to give gold nanoparticles. A 3(3) full factorial design was used to find optimal oxidation conditions of paracetamol on the AuNPs-PA-PGE. The optimal oxidation conditions of drug substance were found as -524 mV for the accumulation potential, 295 s for the accumulation time and pH 8.69 (for the phosphate buffer solution, 0.1 M). The determination of paracetamol was linear in the range of 2.0 x 10(-7)-6.0 x 10(-6) M with a detection limit of 5 x 10(-8) M. As a result, the proposed voltammetric approach gave satisfactory results for the determination of the related drug substance in tablets and syrup.
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    New voltammetric approach to the quantitative estimation of sildenafil citrate in tablets using disposable pencil graphite electrode
    (American Scientific Publishers, 2014) Güzel, Remziye; Ekşi, Haslet; Dinç, Erdal; Solak, Ali Osman
    The voltammetric behavior of sildenafil citrate (SC) was studied through differential pulse stripping voltammetry. The best sensitivity, optimal experimental conditions and settings for the voltammetric method development were obtained by applying experimental design and optimization methodology to the designed sample runs at different accumulation times, accumulation potentials and pHs. The linearity over the concentration range 1 × 10-7 M-8 × 10-6 M for SC was determined and the limit of detection (LOD) was 3.1 × 10-8 M. For the method ability and validity, mean recovery result and relative standard deviation were found to be 99.3% and 2.19%, respectively. The method was applied to the determination of SC in pharmaceutical and plasma samples.
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    A novel surface plasmon resonance enhanced total internal reflection ellipsometric application: electrochemically grafted isophthalic acid nanofilm on gold surface
    (Royal Soc Chemistry, 2011) Ustundag, Zafer; Caglayan, Mustafa Oguzhan; Guzel, Remziye; Piskin, Erhan; Solak, Ali Osman
    The scope of this study is to modify a Surface Plasmon Resonance (SPR) sensor slide with isophthalic acid to evaluate the possible application on the detection of copper(II) ions in aqueous media by total internal reflection ellipsometry. A gold sensor surface was modified by an electrochemical diazonium reduction modification method. The modified surfaces are characterized with cyclic voltammetry (CV) and ellipsometry. Isophthalic acid monolayer modified gold slides were used for in situ detection of aqueous Cu2+ solution with the SPR enhanced total internal reflection ellipsometry (SPRe-TIRE) technique. Layer formation, pH dependency of adsorption, sensor response of the SPRe-TIRE and isothermal kinetic parameters were examined. A high dependency on the number of CV cycles in the monolayer-multiple layer transition was observed. The suggested sensor gave a linear response over a wide range of Cu2+ concentrations. It was also reported that adsorption on the SPRe-TIRE sensor gave Langmuir adsorption model behavior.
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    Preparation and characterization of poly(indole-3-carboxaldehyde) film at the glassy carbon surface
    (Elsevier Science Sa, 2010) Deletioglu, Didem; Hasdemir, Erdogan; Solak, Ali Osman; Ustundag, Zafer; Guzel, Remziye
    Indole-3-carboxaldehyde (In3C) monomer was oxidized by electrochemical methods at the glassy carbon (GC) electrode in 0 05 M tetrabutylammonium tetrafluoroborate in acetonitrile with the aim to prepare a modified electrode Modification was performed using cyclic voltammetry (CV) scanning from 0 0 V to 2 0 V at a scan rate of 50 mV s(-1) for 10 cycles in 1 mM In3C monomer solution The modified GC surface (In3C-GC) was characterized by CV response of potassium ferricyanide and ferrocene redox probes as well as by the electrochemical impedance spectroscopy The modified surface was analyzed by reflection-absorption infrared spectroscopy and compared with the spectrum of the monomeric In3C Elemental composition of the surface was determined by X-ray photoelectron spectroscopy Contact angle measurements was also performed to check the changes in hydrophobic character of the bare GC and compared to that of In3C-GC surface Thickness of the oligomeric/polymeric film was investigated by ellipsometric measurements and a surface confined polymerization mechanism was proposed (c) 2010 Published by Elsevier B V
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    Spectroscopic and Electrochemical Characterization of Benzoylglycine-Modified Glassy Carbon Electrode: Electrocatalytic Effect Towards Dioxygen Reduction in Aqueous Media
    (Taylor & Francis Inc, 2011) Isbir-Turan, Aybuke A.; Ustundag, Zafer; Eksi, Haslet; Guzel, Remziye; Solak, Ali Osman
    Present work aims to create a benzoylglycine (BG)-modified glassy carbon (GC) substrate exploiting the electroreduction of diazonium salts. Dopamine was used to confirm the attachment of benzoylglycine molecules onto the glassy carbon surface by observing the blockage of the electron transfer using cyclic voltammetry (CV). BG-modified GC surface (BG-GC) was also characterized by Raman spectroscopy and electrochemical impedance spectroscopy (EIS) techniques. The ellipsometric thickness of the BG film was measured as approximately 14nm for seven CV cycles. The electrocatalytic effect of BG-GC electrode surface against dioxygen reduction was investigated. The catalytic effect for dioxygen reduction of the BG-GC surface was compared with that of 2-benzo[c]cinnoline, 2-benzo[c]cinnoline 6-oxide- and diethylene glycol bis(2-aminophenyl)ether-modified GC surfaces to clarify the mechanism of catalysis of the surfaces in terms of molecular structure.
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    Synthesis, characterization, and application of silver nanoparticle-thiophenol nanocomposite film on the glassy carbon surface
    (Wiley, 2013) Güzel, Remziye; Ekşi, Haslet; Üstündağ, Zafer; Solak, Ali Osman
    In this study, 4-thiophenol modified glassy carbon electrode was prepared by the reduction of 4-diazothiophenol tetrafluoroborate salt. Silver nanoparticles were attached to the thiophenol modified surface to prepare a thiophenol-silver nanoparticle composite film. 4-Aminothiopenol molecules were deposited by self-assembling technique to form multi-layered nanofilms of TP/SNP/PhNH2 on glassy carbon substrate. These surfaces were characterized by cyclic voltammetry, electrochemical impedance spectroscopy, X-ray photoelectron spectroscopy, reflectance-absorption infrared spectroscopy, and ellipsometry at each multilayer film growth process. Atomic force microscopic images of GC/TP/SNP/PhNH2 surfaces were also acquired. The characterization methods show that the amine group containing surface permits the subsequent modification by a variety of coupling reactions for the immobilization of more complex systems. An application of the electrode modification for the determination of uric acid with a significantly lower detection limit is described. Copyright (c) 2013 John Wiley & Sons, Ltd.