Yazar "Tamer, Ugur" seçeneğine göre listele

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    A novel glucose biosensor platform based on Ag@AuNPs modified graphene oxide nanocomposite and SERS application
    (Academic Press Inc Elsevier Science, 2013) Gupta, Vinod Kumar; Atar, Necip; Yola, Mehmet Lutfi; Eryilmaz, Merve; Torul, Hilal; Tamer, Ugur; Boyaci, Ismail Hakki
    This study represents a novel template demonstration of a glucose biosensor based on mercaptophenyl boronic acid (MBA) terminated Ag@AuNPs/graphene oxide (Ag@AuNPs-GO) nanomaterials. The nanocomposites were characterized by transmission electron microscopy (TEM), X-ray photoelectron spectroscopy (XPS), and X-ray diffraction (XRD) method. The TEM image shows that Ag@AuNPs in the nanocomposite is in the range of diameters of 10-20 nm. The nanocomposite was used for the determination of glucose through the complexation between boronic acid and diol groups of glucose. Thus, a novel glucose biosensor was further fabricated by immobilizing glucose oxidase (GOD) into MBA terminated Ag@AuNPs-GO nanocomposite film (MBA-Ag@AuNPs-GO). The linearity range of glucose was obtained as 2-6 mM with detection limit of 0.33 mM. The developed biosensor was also applied successfully for the determination of glucose in blood samples. The concentration value of glucose in blood samples was calculated to be 1.97 +/- 0.002 mM from measurements repeated for six times. (C) 2013 Elsevier Inc. All rights reserved.
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    Carbon nanotubes/alizarin red S-poly(vinylferrocene) modified glassy carbon electrode for selective determination of dopamine in the presence of ascorbic acid
    (Springer, 2012) Sen, Mine; Tamer, Ugur; Pekmez, Nuran Ozcicek
    A modified electrode was fabricated by electrochemical formation of poly(vinylferrocene) on the multiwall carbon nanotube-alizarin red S matrix covered glassy carbon electrode. A higher electrochemical activity was obtained to the electrocatalytic oxidation of dopamine. The electrode surface was characterized electrochemically and spectroscopically. Poly(vinylferrocene) (PVF) in electrode was used as an electron transfer mediator in the electrochemical oxidation of compounds due to its perfect reversible redox properties. Multi-wall carbon nanotubes (MWCNTs) / alizarin red S (ARS)-PVF electrode was used to the determination of dopamine in the presence of ascorbic acid in 0.1 M sulphate buffer solution at pH 7. The performance of the MWCNTs/ARS-PVF electrode was evaluated by DPV and amperometry.
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    Fabrication and characterization of poly(vinylferrocenium) perchlorate/poly(3,4-ethylenedioxythiophene) composite-coated electrode in methylene chloride
    (Elsevier Science Sa, 2012) Sen Teker, Mine; Tamer, Ugur; Pekmez, Nuran Ozcicek
    Poly(vinylferrocenium) perchlorate/poly(3,4-ethylenedioxythiophene) (PVF+/PEDOT) composite film was synthesized electrochemically on Pt electrode in a methylene chloride solution containing a mixture of poly(vinylferrocene) (PVF) polymer and 3,4-ethylenedioxythiophene monomer. PVF polymer in composite film was used as an electron transfer mediator in the electrochemical oxidation of compounds due to its perfect reversible redox properties. The resulting composite film was characterized electrochemically, spectroscopically and conductivity measurements. Ascorbic acid (AA) was selected as a model compound to evaluate the electrocatalytical ability of the PVF+/PEDOT composite film-coated electrode. The resulting coating exhibits significant electrochemical activity toward AA in 0.1 M phosphate buffer solution at pH 7, with high sensitivity and a wide linearity range. The steady state current vs. the concentration of AA are linear in the range of 2.22 x 10(-4)-6.4 x 10(-2) mol L-1 and 6.4 x 10(-2)-2.16 x 10(-1) mol L-1, respectively, for two linear regions. Limit of detection (LOD) was found to be 6.67 x 10(-5) mol L-1 at 0.35 V vs. SCE. The interaction of AA with PVF+ and PEDOT homopolymer films was investigated electrochemically and spectroscopically. The results showed that the catalytic activity of PEDOT-coated electrode was improved by the addition of PVF+. Applicability of the composite film was investigated by using pharmaceutical tablets, employing amperometric I-t method. (C) 2012 Elsevier B.V. All rights reserved.
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    Nanostructured organic semiconductor films for molecular detection with surface-enhanced Raman spectroscopy
    (Nature Publishing Group, 2017) Yilmaz, Mehmet; Babur, Esra; Ozdemir, Mehmet; Gieseking, Rebecca L.; Dede, Yavuz; Tamer, Ugur; Schatz, George C.
    pi-Conjugated organic semiconductors have been explored in several optoelectronic devices, yet their use in molecular detection as surface-enhanced Raman spectroscopy (SERS)-active platforms is unknown. Herein, we demonstrate that SERS-active, superhydrophobic and ivy-like nanostructured films of a molecular semiconductor, alpha,omega-diperfluorohexylquaterthiophene (DFH-4T), can be easily fabricated by vapour deposition. DFH-4T films without any additional plasmonic layer exhibit unprecedented Raman signal enhancements up to 3.4 x 10(3) for the probe molecule methylene blue. The combination of quantum mechanical computations, comparative experiments with a fluorocarbon-free alpha,omega-dihexylquaterthiophene (DH-4T), and thin-film microstructural analysis demonstrates the fundamental roles of the pi-conjugated core fluorocarbon substitution and the unique DFH-4T film morphology governing the SERS response. Furthermore, Raman signal enhancements up to similar to 10(10) and sub-zeptomole (< 10(-21) mole) analyte detection were accomplished by coating the DFH-4T films with a thin gold layer. Our results offer important guidance for the molecular design of SERS-active organic semiconductors and easily fabricable SERS platforms for ultrasensitive trace analysis.