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    Equivalent device and optical band gaps analysis of acidic red dye imprinted hydrogels
    (Springer, 2022) Coskun, Ramazan; Okutan, Mustafa; Yalcin, Orhan; Ozturk, Muhittin; Kirsoy, Ahmet; Oncan, Mehmet
    Structural, optical and dielectric properties of high quality hydrogels with different doses acidic red dye imprinted were successfully analyzed in detail in this work into provide important information about the technological applications. Absorbance spectra and their energy band gaps for the acidic red dye imprinted hydrogels have been analyzed with UV spectroscopy. The complex dielectric constant, the tangent/dissipation factor (tan delta), the complex impedance, the capacitance and the complex electric modulus were measured in the frequency range of 100 Hz to 40 MHz at room temperature. It has been determined that the peak values of the tangent value in the AR doped samples in the high frequency region are due to the anionic dye effect, unlike the cationic dye doped samples. The dominant effects such as the complex dielectric constant and electric modulus in high frequency region for acidic red dye imprinted hydrogels have been attributed to the Maxwell-Wagner theory, the basis of Kroop's approach and the ionic conductivity. Experimental plane plots (Cole-Cole plots) of the complex dielectric constant, impedance and electric modulus for different doses acidic red dye imprinted hydrogels were obtained. In order to analyze the suitability of the samples for electrical circuit applications, the equivalent electrical circuit corresponding to the Cole-Cole plots for the complex electric modulus was calculated and adapted with Smith Chart.
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    Evaluation of quality the pumpkin, wild plum, pear, cabbage traditional homemade vinegars using the spectroscopy and rheology methods
    (Pergamon-Elsevier Science Ltd, 2021) Ozturk, Muhittin
    In this study, the quality evaluation of homemade pumpkin, pear, wild plum and cabbage vinegar produced by traditional methods was carried out using the ultraviolet (UV) spectroscopy, rheology technique and Fourier transform infrared (FTIR) spectroscopy method. The measurement of UV spectra, flow behaviours and infrared spectral fingerprints of all the vinegars were performed in the wavelength range of 190 nm to 600 nm, shear rate of 10(-3) s(-1) to 10(2) s (1) and wavenumber of 4200 c(-1) to 400 cm(-1) at room temperature, respectively. The quality of homemade vinegars was correlated with the UV spectra peaks, which took values with acetic acid and phenolic compound concentrations. It was determined that the absorption coefficient and optical energy gaps (Eg) which were caused by the release time, depends on the organic acids content. It was observed that the UV spectra and forbidden energy gaps of all the vinegars compatible with the Lambert-Beer-Bouguer and Tauc laws, respectively. The flow behaviour of homemade vinegars was consistent with the non-Newtonian flow, which is the signature behaviour of the dilatant (thickening) and pseudo-plastic (thinning) liquids. Moreover, it was determined that the spectral fingerprint peaks obtained from FTIR spectroscopy were caused by the mixture of acetic acid and water forming the structure of the vinegar. As a result of spectroscopy and rheological analyses, which yields compatible results with commercial tests, it is predicted that it can be safely used as health test. (C) 2021 Elsevier B.V. All rights reserved.
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    Fullerene C60: Dielectric and elastic properties of E8 nematic liquid crystal
    (Elsevier, 2024) Okutan, Mustafa; Ozturk, Muhittin; Yesilot, Gursel; Yalcin, Orhan; Bolivar, Peter Haring
    This study presents a comprehensive analysis of the impact of Fullerene C60 doping on the dielectric and elastic behavior of E8 coded nematic liquid crystals. By investigating the underlying mechanisms, we unveil how Fullerene C60 can effectively modify the properties of nematic liquid crystals, particularly their dielectric and elastic characteristics. Through the analysis of Cole-Cole plots and semicircle plots, we gain valuable insights into the suitability of an equivalent electronic circuit model, thereby holding promise for liquid crystal-based devices with improved performance and functionality in electrical circuit applications. Furthermore, our results demonstrate that the presence of Fullerene C60 induces higher splay elastic constant (K11) values in doped nematic liquid crystals, attributed to an increase in the sample's threshold voltage. Moreover, the presence of Fullerene C60 fosters strong elastic interactions in the liquid crystal system due to surface anchorage, resulting in an elevation of its elastic energy.
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    Impedance characterization of hydrothermally synthesized nickel zinc ferrite nanoparticles for electronic application
    (Elsevier, 2024) Okutan, Mustafa; Ozturk, Muhittin; Okutan, Sonay; Yesilot, Gursel; Yalcin, Orhan; Bablich, Andreas; Bolivar, Peter Haring
    This study comprehensively investigates the structural, morphological, dielectric, and conductivity properties of Ni0.5Zn0.5Fe2O4 nanoparticles synthesized through a hydrothermal method, focusing on their suitability for technological applications. The nanoparticles exhibited a cubic structure with an average grain size of approximately 19 nm. The dielectric properties were analyzed with respect to frequency and temperature, showcasing behaviors consistent with Maxwell-Wagner and Koop's theories. The dielectric plane plots, corresponding to the impedance circuit in the Smith Chart, were found to align with the Davidson-Cole relaxation model. Moreover, the conductivity properties adhered to the Jonscher Power law, resembling conductive properties akin to semiconductors in accordance with the band theory. Notably, the s parameter, indicative of the DC conduction mechanism, displayed temperature-dependent variations, suggesting compatibility with the small polar and correlated hopping barrier conduction models. The thermal activation energies of the Ni0.5Zn0.5Fe2O4 nanoparticles at 102, 103, 104, 105, and 106 rad/s frequencies have been recorded at 0.115, 0.141, 0.157, 0.133 and 0.121 eV, respectively. The experimental results strongly suggest that Ni0.5Zn0.5Fe2O4 nanoparticles hold promise as an inspiring material for electronic circuit applications.
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    The effects of lithographic residues and humidity on graphene field effect devices
    (INDIAN ACAD SCIENCES, 2017) Kantar, Behiye Boyarbay; Ozturk, Muhittin; Cetin, Hidayet
    Recently, unknown-manner changes in charge neutrality point (CNP) positioning were ascribed to humidity at graphene field effect transistors (GFETs). While the exact means of humidity interacting with hydrophobic graphene remains unknown, this work examines pristine and lithographic-process-applied graphene surfaces with surface enhanced Raman spectra (SERS). SERS analysis shows that the lithographic-process-applied graphene does not have the same properties as those of pristine graphene. Furthermore, this study has experimentally investigated the effect of humidity on the transfer characteristics of GFET and proposed a model to explain the formation of asymmetric IDS-Vbg branches in accordance with the SERS results and humidity responses.