Browsing by Author "Kaygili O."

Now showing 1 - 6 of 6

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.
Comparison of experimental photonic and refractive index characteristics of the TBADN films with their theoretical counterparts
(2018-03-16) Örek C.; Arslan F.; Gündüz B.; Kaygili O.; Bulut N.
Photonic properties and refractive indexes of the TBADN films were investigated with various experimental and theoretical methods. The effects of the film thicknesses on the photonic properties of the TBADN films were examined. It was found that while the optical band gap of the TBADN film decreases with increasing film thickness, the refractive indexes exhibit a normal dispersion behavior for both experimental and theoretical techniques. This study shows that the most suitable optoelectronic parameters for optoelectronic devices can be achieved with film thicknesses. The TBADN molecule was found to have a lower refractive index in the chloroform solvent.
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.
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.
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.