Browsing by Author "Orek C."

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An experimental and theoretical investigation of the structure of synthesized ZnO powder
(2018-09-24) Kaygili O.; Ercan I.; Ates T.; Keser S.; Orek C.; Gunduz B.; Seckin T.; Bulut N.; Bañares L.
ZnO powder has been synthesized, characterized experimentally and its theoretical modeling carried out by density functional theory (DFT). The experimental and theoretical results were compared with each other and with the available data in the literature. A detailed crystal structure analysis was carried out using X-ray diffraction (XRD) data. Experimental and theoretical FTIR analysis, energy gap and density of states and electronic band structure calculations have been done for a complete characterization of the material. The surface morphology has been investigated by scanning electron microscopy (SEM) and energy dispersive X-ray (EDX) spectroscopy. It has been found that the electron excitation of ZnO can occur most probably at the Γ-Γ point, where the energy gap has the lowest value between the valance and conduction bands.
Computational Study of Doping in Dopamine with Halogens to Control Optical and Spectroscopic Properties
(2023-06-13) Nasidi I.I.; Orek C.; Majid A.; Eldin S.M.; Kaygili O.; Bulut N.
In this research, a comprehensive study of dopamine was conducted using the theoretical first principles method due to its crucial importance as a hormone for the neurotransmission process in the animal body. Many basis sets and functionals were used for optimization of the compound to attain stability and find the appropriate energy point for the overall calculations. Then, the compound was doped with the first three members of the halogen family (fluorine, chlorine, and bromine) to analyze the effect of their presence in terms of change in their electronic properties, such as band gap and density of states, and spectroscopic parameters, such as nuclear magnetic resonance and Fourier transform infrared. It was found that the band gap of the system changes depending on the doping of halogens.
Electronic, optical, and spectroscopic analysis of TBADN organic semiconductor: Experiment and theory
(2017-01-01) Orek C.; Gündüz B.; Kaygili O.; Bulut N.
In this study, the electronic, optical and spectroscopic properties of 2-tert-Butyl-9,10-di(naphth-2-yl) anthracene (TBADN) semiconductor in different solvents were investigated by experimentally and computationally. Obtained theoretical and experimental UV–VIS spectra of the TBADN were found to be quite in good agreement and can be controlled with various solvents. Refractive index values of the TBADN semiconductor in different solvents were experimentally measured and calculated theoretically. Finally, the FTIR spectra of the TBADN organic semiconductor in different solvents were investigated by theoretical and experimental methods. It was found that the band gap is sensitive to the concentration of the solute.
Experimental and Theoretical Investigations Regarding the Thione–Thiol Tautomerism in 4-Benzyl-5-(thiophene-2-yl)-2,4-dihydro-3H-1,2,4-triazole-3-thione
(2021-01-01) Sarac K.; Orek C.; Koparir P.
Abstract: The title compound was synthesized by ring-closure reaction of thiophene-2-carbohydrazide with benzyl isothiocyanate and characterized using spectroscopic methods (NMR and FT-IR). Quantum chemical calculations at the B3LYP/6-311++G(d,p) level were carried out to examine its molecular and spectroscopic properties, thione–thiol tautomerism, and proton transfer reaction. The structural and spectroscopic results were well consistent with the experimental data. The solvent effect on the proton transfer reaction was examined using three solvents (acetone, ethanol, and dimethyl sulfoxide) through the polarizable continuum model (PCM) approximation (direct solvent effect) and solvent-assisted mechanism. A high energy barrier was determined for the interconversion of the thione and thiol forms in both gas and solution phases. Even though the presence of solvent molecules significantly reduced the barrier to proton transfer, it was insufficient for the reaction to occur. The corresponding thermodynamic parameters and the energy difference between the HOMO and LUMO of the thione and thiol tautomers were calculated.
Structures and optical properties of zinc oxide nanoclusters: a combined experimental and theoretical approach
(2023-07-05) Orek C.; Keser S.; Kaygili O.; Zuchowski P.; Bulut N.
CONTEXT: In this study, theoretical and experimental analysis of the electrical, optical, and structural properties of a wurtzite-like zinc oxide (ZnO) nanostructure has been done. To investigate how quantum confinement affects the optical characteristics, two distinct ZnO clusters in nanowire structures have been investigated. The [(ZnO)55(H2O)4] system's HOMO-LUMO band gap (BG) was calculated to be 2.99 eV, which is quite close to the experimental measurement. It was found that the BG decreases with the increase in the number of atoms in the cluster in connection with the quantum confinement in nanoclusters. In addition, the lowest excitation energy in TD-DFT calculations of the identical system is in fairly good agreement with the experimental value with a difference of 0.1 eV. We conclude that the CAM-B3LYP functional has highly successful in reproducing the experimental data reported in the present study and previously reported experimental data. METHODS: The geometrical optimization of two different sizes of ZnO clusters ([(ZnO)25(H2O)4] and [ZnO)55(H2O)4]) was performed using the CAM-B3LYP functional with no symmetry constraints applied in the gas phase. LANL2DZ basis sets were used for the Zinc (Zn) atom and 6-31G* basis sets for the O and H atoms. To determine their optical and electronic properties, excited state calculations of the pre-optimized structures were performed using the Time-Dependent DFT (TD-DFT) method. Multiwfn, Gaussum 3.0, and GaussView 5.0 programs were used to visualize the results.
Synthesis, characterization and biological activities evaluation of novel sulfanyl derivatives
(2020-03-03) Saraç K.; Orek C.; Koparir M.
A novel series of 1-(3-Methyl-3-mesityl)-cyclobutyl-2-{[5-(2-fluorophenyl)-4-(aryl-alkyl)-4H-[1,2,4]triazol-3-yl]sulfanyl}-ethanone compounds were synthesized by a condensation reaction. The new compounds were characterized by elemental analyses, FT-IR and 1H, 13C NMR techniques. The antioxidant and antibacterial properties of the synthesized compounds were also investigated. The in vitro antioxidant and antibacterial activities of the newly synthesized compounds were measured, and they were found to exhibit significantly high antioxidant activity.
Synthesis, structure, cytotoxic and antioxidant properties of 6-ethoxy-4-methylcoumarin
(2020-04-05) Celikezen F.C.; Orek C.; Parlak A.E.; Sarac K.; Turkez H.; Tozlu Ö.Ö.
Coumarins have a wide usage area in medicinal applications. It is known that the design and synthesis of new coumarin derivatives are performed to prepare new drugs in many laboratories. The aim of the study was to synthesize 6-ethoxy-4-methylcoumarin and detect its chemical and biological properties for the first time. 6-ethoxy-4-methylcoumarin was synthesized using Pechmann method. Atomic orbital (GIAO) 1H and 13C NMR chemical shift values in the ground state were calculated and Density Functional Method (DFT) was applied with the 6–311++G (d, p) basis set to determine chemical properties. 6-ethoxy-4-methylcoumarin was applied to cultured blood samples at various concentrations (10–400 mg/L) for determining biological activity. 3-(4,5-dimethylthiazol-2-yl)-2,5 diphenyltetrazolium bromide (MTT) and lactate dehydrogenase (LDH) release assays were used to evaluate cytotoxic effect. In addition, total antioxidant capacity (TAC) and total oxidative status (TOS) were examined to determine antioxidant properties. The results showed that theoretical vibrational frequencies and chemical shift values were close to experimental values. Moreover, 6-ethoxy-4-methylcoumarin showed a slight cytotoxic effect at dose of 200 mg/L and exhibited an antioxidant activity at 25 mg/L concentration without changing oxidative status at all of doses.
Temperature dependent structural and vibrational properties of hydroxyapatite: A theoretical and experimental study
(2017-12-01) Kebiroglu M.H.; Orek C.; Bulut N.; Kaygili O.; Keser S.; Ates T.
We describe the temperature dependence of the vibrational, rotational and translational partition functions of the activated complex of hydroxyapatite (HAp). Computed data show that the vibrational modes have a larger contribution towards the partition function of HAp compared to the rotational and translational contributions. X-ray diffraction (XRD), and Fourier transform infrared (FTIR) spectroscopy have been applied for HAp in the temperature range from 730 °C to 1030 °C at steps of 100 °C. Temperature dependent density functional theory (DFT), B3LYP, and Ground State Hartree-Fock (HF) with 6–311G basis set calculations were also applied to HAp to calculate FTIR spectra, HOMO, and LUMO energies, and density of states (DOS), and the results have been compared to experimental findings. The present results underline that experimental measurements and theoretical calculations of unit cell parameters, and the intensities of most of the FTIR data for HAp are nearly independent on temperature.