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    Effect of Pre-Treatment Time On Graphene Nanosheets Produced by Exfoliation Method
    (Electrochemical Soc Inc, 2023) Guzel, Tamer; Islek, Yasemin; Yildiz, Oguzhan
    2D-Materials are the biggest candidates to take today's electronic technology to a new point. In particular, graphene can find its place in many areas due to its unique properties. This has made the investigation of the factors that can affect the quality of graphene production up-to-date. In the present study, effect of pre-treatment time on graphene nanosheets produced was investigated. The structural analyses were carried out by X-ray diffraction spectroscopy (XRD), Raman spectroscopy, and Fourier Transform Infrared Spektrometresi (F-TIR). The morphological analyses of the surface were performed using scanning electron microscopy (SEM). The number of layers and crystallite of graphene nanoparticles was calculated and the results were compared with the literature. The results show that the pre-treatment time affects the structural properties of the graphene nanosheets produced by the exfoliation method and there is a more positive effect on exfoliated graphene quality for 20 min pre-treatment time.
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    Electron paramagnetic resonance study of gamma (gamma)-irradiated methyl 4-methyl benzoate (C9H10O2)
    (TAYLOR & FRANCIS LTD, 2016) Karatas, Ozgul; Aras, Erdal; Karadag, A. Halide; Islek, Yasemin
    In this study, gamma ()-irradiated methyl 4-methyl benzoate (C9H10O2) single crystals were investigated and the structure of the free radical occurring by -irradiation was determined by using Electron paramagnetic resonance (EPR) technique. C9H10O2 single crystals were produced by slow evaporation with distilled water solution at room temperature. These single crystals were irradiated by Co-60-gamma-ray source with a dose speed of 0.981kGy/h at room temperature for 72h. The EPR spectra of irradiated C9H10O2 single crystals were recorded between 125 and 400K temperatures in steps of 10 degrees intervals at different orientations in magnetic field with an X-band EPR spectrometer. The spectra were found to be slightly anisotropic and temperature independent; taking into consideration the chemical structure with experimental data we found only one free radical structure The radical structure was simulated using the Bruker software WinEPR-Simfonia and the experimental g-value with anisotropic hyperfine coupling constants of radical were calculated as follows: g = 2.0124, aCH(4) = 26.51G, aCH(3) = 5.45G.
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    EPR study of gamma-irradiated cholesteryl methyl carbonate
    (ELSEVIER SCIENCE BV, 2014) Aras, Erdal; Islek, Yasemin; Karatas, Ozgul; Abbass, Hind Kh; Birey, Mehmet; Kilic, Ahmet
    The electron paramagnetic resonance (EPR) of gamma-irradiated single crystals of cholesteryl methyl carbonate (C29H48O3) has been studied for different orientations of the crystals in a magnetic field. EPR spectra of cholesteryl methyl carbonate (C29H48O3 irradiated by Co-60-gamma were recorded between 125 K and 300 K for different orientations of the crystal in the magnetic field. The spectra were found to be temperature independent. In C29H48O3 single crystal,. the radiation damage centers caused by a Co-60-gamma source were determined as CH3CH2CH radical. For CH3CH2CH radical, a value of spectroscopic splitting factor g was calculated and experimentally results were supported by simulation program (WinEPR). (C) 2014 Elsevier B.V. All rights reserved.