Browsing by Author "Erbas, SÇ"

Now showing 1 - 7 of 7
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    Synthesis and Spectroscopic Studies of Phenanthroimidazole-Imine Derivatives and Evaluation of Their Antioxidant Activity
    Gülle, S; Erbas, SÇ; Uzel, A
    The phenanthroimidazole derivatives are used in the drug industry in large scale. In this study four new phenanthroimidazole-imine derivatives were synthesized and their spectroscopic studies as well as their antioxidant behaviors were examined. Structural analyses were made by FT-IR, H-1-NMR, C-13-NMR, LC-MS spectroscopy techniques. UV-vis absorption and emission spectroscopy techniques have been used to determine the photophysical characteristics of four newly synthesized phenanthroimidazoles. The maximum absorption and emission wavelengths, molar extinction coefficients (epsilon), singlet energy levels (Es), Stokes' shift values (Delta lambda) of phenanthroimidazole-imine derivatives are given. Additionally, the antioxidant behavior of all compounds were investigated which the ascorbic acid used as standard molecule in present study.
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    Investigation of spectroscopic and thermo-mechanical behaviors of different phenanthroimidazole-azo dyes in solvent and polymer medium
    Erbas, SÇ; Uregil, U; Gülle, S; Bastürk, SB
    The aim of this study is the investigation of the interaction between dyes and polymers which have different polarities. Dye doped polymer films have larger application areas because of the fact that dye is more stable when doped in polymer compared to solvent medium. However, dye dispersion in the polymer medium affects both the spectroscopic and mechanical properties of the polymer. The polymer-dye interaction must be high for a good dispersion,. In this study, polypropylene with apolar character and polymethylmethacrylate with polar groups were chosen as a solid phase to examine polymer-dye interactions. The photophysical properties of phenanthroimidazole-azo compounds synthesized previously were examined with UV-visible and fluorescence spectroscopy techniques in tetrahydrofuran and two polymer media. Also, photostability tests of azo dyes in THF and polymer films were performed. Surface roughness characterizations of polymer films were carried out with AFM. Additionally, the viscoelastic behaviors of the polymethylmethacrylate and polypropylene films under sinusoidal vibrations at different temperatures were studied by dynamic mechanical analysis technique.
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    A Selective Fluorescence Sensor for Fe (III) Based on Phenanthroimidazole Imine Compound
    Gülle, S; Erbas, SÇ
    Experimental studies in the aqueous solution are crucial for the detection of metal cations in environmental and biological media. Polymer materials allow to work in aqueous media for fluorescent substances which are insoluble in water. Fluorescence sensor studies of the phenanthroimidazole imine compound (PI) synthesized previously by our group were performed in the polymer medium and the selective response to Fe (III) cation was obtained. The resulting sensor exhibited a selective fluorescence quenching effect to Fe (III). A logarithmic calibration graph was obtained in the range of 5.0 x 10(- 5) and 1.0 x 10(- 2) M. The interference effects of other ions besides Fe (III) have been examined and it has been observed that PI compound behaves selectively to Fe (III) ion in aqueous media. In addition, regeneration and reproducibility studies were carried out to determine the long-term usage of PI doped polymer film and reproducible results have been obtained for Fe (III) cation.
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    Preparation and characterization of strontium aluminate/urea-formaldehyde composite: a solution for oxidation-induced darkening problem
    Koçak, G; Erbas, SÇ
    Purpose This study aims to produce homogenously prepared polymer composites by adding two different strontium aluminate derivatives (Sr4Al14O25 and SrAl2O4) to urea-formaldehyde (UF) at different mass concentrations. In the context of this work those strontium-based derivatives were compared in terms of mechanical and luminescent characteristics. Additionally, sodium bicarbonate was integrated with the prepared composites to eliminate/minimize darkening problem, which might arise from the oxidation of Eu +2 to Eu2O3, on the surface of strontium aluminate/urea-formaldehyde composites. Design/methodology/approach In this study, strontium aluminate/UF composite materials were produced using a compression molding technique. Their mechanical, thermomechanical and luminescence properties were investigated via various characterization methods. Particle size analysis was used to characterize phosphor derivatives, whereas scanning electron microscopy with energy dispersive X-ray spectroscopy (SEM-EDX) was conducted for morphological examination. Findings The darkening problem was prevented by the introduction of sodium bicarbonate into the composite systems. Based on the characterization and test results, the only addition of strontium aluminate reduced the mechanical properties. However, it was seen that the introduction of sodium bicarbonate into the composites improved those properties positively. The appropriate amounts of strontium aluminate and sodium bicarbonate were determined by conducting an experimental optimization study. The optimum composition of the composite materials was obtained by introducing 2% phosphor and 3% NaHCO3. Originality/value The approach used in this study has provided a method to solve the darkening problem, which degrades the aesthetic appearance in industrial production.
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    Synthesis of Novel Phenanthroimidazole Based Beta-Diketone Compounds: Investigation of Their Spectroscopic Properties and Electrochemical Characterization
    Gülle, S; Erbas, SÇ; Polatoglu, I
    In this study, three new phenanthroimidazole based beta-biketone compounds containing different donor (methoxy and dodecyloxy) and acceptor (cyano) groups were synthesized. Spectroscopic and electrochemical properties of the synthesized compounds were studied. FTIR, 1H-NMR, 13C-NMR, and LC-MS/MS were carried out for the structural analyses of the phenanthroimidazole derivatives. UV-vis absorption and emission studies were also carried out in the solvents with different polarities. High molar absorption coefficients and high Stokes' shift values were observed. The photostability of these derivatives was measured in all the solvents used. These values suggest that the derivatives could be used in fluorescence imaging applications for various biological and analytical purposes. Furthermore, the potential use of these molecules as electron transfer mediators for the electrochemical behavior of biological material was investigated. All the curves were also simulated using the most suitable equivalent Randles circuit. The charge-transfer resistance values varied depending on the donor and acceptor groups in the synthesized molecules. The Nyquist plots were evaluated, and it was observed that these molecules exhibit different resistance to electron transfer. These synthesized molecules can potentially be used as electron transfer mediators in the electrochemical detection of biological analytes.
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    FABRICATION AND CHARACTERIZATION OF NANOCLAY-REINFORCED THERMOPLASTIC COMPOSITE FILMS
    Erbas, SÇ; Bastürk, SB
    A number of nanoclay/poly(methyl methacrylate) (PMMA) composite films were prepared with three different clay concentrations (0.5 %, 1 % and 2 % (w/%)) via a solution-casting process. The nanoclay was modified by applying different compatibilization techniques: mere silane surface treatment and surfactant application with the addition of a silane agent. The interlayer distances of the clay galleries were determined using X-ray diffraction (XRD) and the modifications were verified with Fourier-transform infrared spectroscopy (FTIR) analysis. The dynamic mechanical analyses (DMA) were performed to clarify the viscoelastic properties of the produced films. Morphological characterizations were carried out with a scanning electron microscope (SEM). The neat clay/PMMA composites and pure PMMA film were also used to compare the effects of the compatibilization methods. The silane-modified clay/PMMA composites exhibited the best performance, as compared to neat PMMA, by considering the storage modulus (17.7 % increase) and the glass-transition temperature (20 % increase). However, in terms of the dynamic mechanical properties, the joint implementation of these two modification techniques did not satisfy the expectations, probably due to the excess modifier and the plasticizing effect.
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    Novel organic dyes based on phenyl-substituted benzimidazole for dye sensitized solar cells
    Saltan, GM; Dinçalp, H; Kiran, M; Zafer, C; Erbas, SÇ
    Two new sensitizers derived from benzimidazole core for dye-sensitized solar cell (DSSC) applications were designed and synthesized as D-pi-A structures, in which two phenyl-substituted benzimidazole group, a phenyl ring and a cyanoacrylic acid were used as the electron donor, pi-conjugated linkage and the electron acceptor, respectively. Effect of methoxy- and N,N-dimetylamino- moieties attached to the phenyl groups of benzimidazole were investigated by means of optical and photovoltaic measurements. The compounds exhibit broad absorption maximum at 387 nm with the tail extending up to 500 nm on TiO2-coated thin film. The longer wavelength absorption band around 360 nm and the much longer decay components could be attributed to the existence of charge transfer state of the dyes in solutions. DSSC device fabricated by using methoxy substituted dye (BI5a) as a sensitizer shows much better incident photon-to-current conversion efficiency (IPCE) of 64% giving cell efficiency of 2.68%. (C) 2015 Elsevier B.V. All rights reserved.