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Öğe Ab-initio and DFT methodologies for computing hyperpolarizabilities and susceptibilities of highly conjugated organic compounds for nonlinear optical applications(ELSEVIER SCIENCE BV, 2016) Karakas, A.; Karakaya, M.; Ceylan, Y.; El Kouari, Y.; Taboukhat, S.; Boughaleb, Y.; Sofiani, Z.In this talk, after a short introduction on the methodologies used for computing dipole polarizability (alpha), second and third-order hyperpolarizability and susceptibility; the results of theoretical studies performed on density functional theory (DFT) and ab-initio quantum mechanical calculations of nonlinear optical (NLO) properties for a few selected organic compounds and polymers will be explained. The electric dipole moments (mu) and dispersion-free first hyperpolarizabilities (beta) for a family of azo-azulenes and a styrylquinolinium dye have been determined by DFT at B3LYP level. To reveal the frequency dependent NLO behavior, the dynamic a, second hyperpolarizabilities (gamma), second (chi((2))) and third-order (chi((3))) susceptibilites have been evaluated using time-dependent HartreeFock (TDHF) procedure. To provide an insight into the third-order NLO phenomena of a series of pyrrolo-tetrathiafulvalene-based molecules and pushpull azobenzene polymers, two-photon absorption (TPA) characterizations have been also investigated by means of TDHF. All computed results of the examined compounds are compared with their previous experimental findings and the measured data for similar structures in the literature. The one-photon absorption (OPA) characterizations of the title molecules have been theoretically obtained by configuration interaction (CI) method. The highest occupied molecular orbitals (HOMO), the lowest unoccupied molecular orbitals (LUMO) and the HOMO-LUMO band gaps have been revealed by DFT at B3LYP level for azo-azulenes, styrylquinolinium dye, push-pull azobenzene polymers and by parametrization method 6 (PM6) for pyrrolo-tetrathiafulvalene-based molecules. (C) 2016 Elsevier B.V. All rights reserved.Öğe Analysis of Poly (2-Hydroxyethyl Methacrylate)-co-Poly (4-Vinyl Pyridine) Copolymers [COP2,4] Irradiated: an EPR study(POLISH ACAD SCIENCES INST PHYSICS, 2016) Ceylan, Y.; Aydogmus, H. Yumurtaci; Usta, K.; Usta, A.; Ceylan, N.; Yilmaz, H.Poly(2-hydroxyethyl methacrylate)-co-poly(4-vinyl pyridine) and poly(HEMA)-co-poly-(4-VP) copolymers were synthesized by free radical polymerization. K2S2O8 was used as an initiator. Chain lengths of the copolymer was changed by varying the monomer/initiator ratio. These polymers have molarites of 2.6 and 2.1 respectively and are called COP2 and COP4. The samples were exposed to gamma rays at room temperature. After irradiation, the EPR spectra of COP2 and COP4 were recorded between 120 K and 450 K. From the temperature dependence of the line intensity, it was concluded that unpaired spin concentration in the irradiated samples has been changing with temperature. A theoretical study, presented in this report, was aimed to test success of the machine learning methods and to select the best learning method.Öğe Comparative Study of Influences of Gamma Rays on Calix[4]Arene and 25,27-di(4-Nitrobenzyl)-26,28-Dihydroxycalix[4]Arene: EPR Study(POLISH ACAD SCIENCES INST PHYSICS, 2017) Ceylan, Y.; Usta, K.; Ceylan, N.; Usta, A.; Koc, Y.In the present study, calix[4]arene and its derivate 25,27-di(4-nitrobenzyl)-26,28-dihydroxycalix[4]arene were irradiated for 72 hours by Co-60 gamma rays at dose rate of 0.720 kGy/h. These irradiated samples were analyzed by EPR method and it was found that one type of radical was produced in calix[4]arene, and two type of radicals were produced in 25,27-di(4-nitrobenzyl)-26,28-dihydroxycalix[4]arene. The measurements were performed in the temperature range of 273-400 K using x-band EPR spectrometer. It was observed that the spectra, obtained from two samples, have very weak temperature dependence. Hyperfine and g parameters were calculated for two samples.Öğe Computational studies on linear, second and third-order nonlinear optical properties of novel styrylquinolinium dyes(ELSEVIER, 2016) Karakas, A.; Karakaya, M.; Taser, M.; Ceylan, Y.; Gozutok, A.; Arof, A. K.; El Kouari, Y.The electric dipole moments (mu), static dipole polarizabilities (alpha) and first hyperpolarizabilities (beta) of styrylquinolinium dyes, D8 and D21, have been computed by density functional theory (DFT). The one photon absorption (OPA) characterizations have been investigated using UV-vis spectroscopy and further interpreted using computational chemistry. The time-dependent Hartree-Fock (TDHF) method has been used to describe the dynamic dipole polarizabilities, dynamic second-order and also static and dynamic third-order nonlinear optical (NLO) properties. D8-D21 have rather high beta and second hyperpolarizabilities (gamma). The highest occupied molecular orbitals (HOMO), the lowest unoccupied molecular orbitals (LUMO) and the HOMO-LUMO band gaps for D8-D21 have been evaluated by DFT. (C) 2016 Elsevier B.V. All rights reserved.Öğe An EPR Study on Radiation-Induced 2-(piperidin-1-ylmethyl) phenol Single Crystal(POLISH ACAD SCIENCES INST PHYSICS, 2016) Usta, K.; Ceylan, Y.; Usta, A.; Ceylan, N.; Aras, E.For the assessment of irradiation influence on 2-(piperidin-1-ylmethyl) phenol single crystals (C12H17NO), electron paramagnetic resonance measurements were carried out on the samples exposed to Co-60 radiation at dose values of 22.8, 45.6 and 68.4 kGy at room temperature. Electron paramagnetic resonance signals were not observed in non-irradiated sample and in samples irradiated at dose values of 22.8 and 45.6 kGy. The electron paramagnetic resonance measurements were performed on the single crystals. This irradiated single crystal was rotated in steps of 10 degrees. One type of radical center was found. The average values of g and hyperfine constant of the detected radiation damage center were calculated from experimental spectra as follows: g = 2.0052, A(H) = 0.74 mT.Öğe An EPR study on radiation-induced 4-hydroxyphenyl-acetic acid polycrystalline(ELSEVIER SCIENCE BV, 2015) Ceylan, Y.; Usta, K.; Usta, A.; Aydogmus, H. Yumurtaci; Guner, A.To determine of irradiation effect on 4-hydroxyphenyl-acetic acid polycrystalline, electron paramagnetic resonance (EPR) measurements were carried out. Two samples were used, which were given dose of 22.8 and 49 kGy by gamma rays using Co-60-source. EPR signals were not observed from irradiated sample, taken dose of 22.8 kGy. The measurements were performed on the sample, absorbed dose of 49 kGy, at the temperature between 120 K and 450 K. The two radical structures were suggested within experimental error. Though the radicals are identical, it was determined that they have different EPR parameters. It was observed that the intensities of the EPR spectra were to be dependent on the temperature. Also, in this study, it was aimed to test success of the machine learning methods to select the best method can be implemented theoretically. (C) 2015 Elsevier B.V. All rights reserved.Öğe An ESR Study on 2,4 Diaminotoluene Exposed to Gamma Rays and Application of Machine Learning(POLISH ACAD SCIENCES INST PHYSICS, 2016) Ceylan, Y.; Usta, K.; Aydogmus, H. Yumurtaci; Usta, A.; Ceylan, N.; Aras, E.The polycrystals of 2,4 diaminotoluene were produced by slow evaporation of solvent. The polycrystalline samples were exposed to Co-60 gamma rays with dose rate of 0.950 kGy/h, at room temperature, for 12, 24, 48, and 72 hours. The electron paramagnetic resonance measurements were carried out on these samples in the temperature range between 298 K and 400 K. No electron paramagnetic resonance signal was observed in the samples irradiated for 12, 24, 48 hours. Two types of radicals were detected using ESR spectrometer in the sample irradiated for 72 h. These radiation damage centers were called RI and RII. The average values of g and the hyperfine coupling constant were calculated. This study also investigates the potential usage of machine learning methods and aims to test the success of these methods and to select the best method.Öğe Evaluation of Antioxidant Activity, Phytochemicals and ESR Analysis of Lavandula Stoechas(POLISH ACAD SCIENCES INST PHYSICS, 2015) Ceylan, Y.; Usta, K.; Usta, A.; Maltas, E.; Yildiz, S.The antioxidant activity of phytochemicals and of the methanolic extract of Lavandula stoechas was evaluated by beta-carotene-linoleate bleaching, DPPH radical scavenging, ferric reducing/antioxidant power (FRAP). The obtained results were compared with antioxidant activities of synthetic antioxidants, such as BHT and BHA. The highest antioxidant activity of the extract was observed by DPPH radical scavenging assay, which was 84.45 +/- 5.1 % at 1 mg ml(-1). Rutin, rosmarinic acid, and caffeic acid were main phenolics in the extract. The total phenolic content of the methanolic extract of Lavandula stoechas was found to be 105.5 +/- 2.7 mg gallic acid equivalent (GAE). Electron spin resonance (ESR) measurements were also performed on the samples. Free radicals were determined by ESR method. g value was found to be 2.0034 for the Lavandula stoechas; 2.0052 for quercetin.Öğe In Vitro Analysis of AHPlus and MM-Seal by ESR and Thermoanalytical Methods(POLISH ACAD SCIENCES INST PHYSICS, 2015) Ceylan, Y.; Usta, A.; Usta, K.; Cobankara, F. Kont; Yildirim, C.; Birey, M.The free radicals and their concentration in resin materials may impact biocompatibility and polymerization properties of dental materials. The aim of this study was to determine whether there are free radicals and to obtain useful information about thermal stability of materials using electron spin resonance (ESR) spectroscopy, TGA (Thermogravimetry Analysis) and DTA (Differential Thermal Analysis) methods. Epoxy resin-based sealers AHPlus and MM-Seal samples, freshly mixed and set, were prepared to be analysed with ESR and thermal methods. The free radicals were found in dental materials. As radical concentration in AHPlus have changed very slowly, the concentration in MM-Seal have decreased dramatically. Also, MM-Seal was found to decompose in three steps with the increasing temperature, while decomposition of the AHPlus occurred in two steps.Öğe One-photon Absorption Characterizations, Dipole Polarizabilities and Second Hyperpolarizabilities of Chlorophyll a and Crocin(SCIENDO, 2018) Karakas, A.; Ceylan, Y.; Karakaya, M.; Taser, M.; Terlemez, B. B.; Eren, N.; El Kouari, Y.The dispersion-free dipole polarizability (alpha) computations for chlorophyll a (1) and crocin (2) have been achieved by density functional theory (DFT) at B3LYP/ 6-31G(d) level. The measured one-photon absorption (OPA) wavelengths are quite consistence with the theoretically obtained values. Ab-initio quantum chemical calculations (time-dependent Hartree-Fock (TDHF)) have been implemented to reveal the static second hyperpolarizabilities (gamma) and dynamic dipole polarizabilities of the title molecules. The examined compounds display gamma with non-zero values, introducing their third-order nonlinear optical (NLO) phenomena. The first and second frontier molecular orbitals of the investigated molecules have been also derived from DFT.Öğe Optical and structural characterization of thin films containing metallophthalocyanine chlorides(ELSEVIER SCI LTD, 2015) Zawadzka, A.; Karakas, A.; Plociennik, P.; Szatkowski, J.; Lukasiak, Z.; Kapceoglu, A.; Ceylan, Y.The structural and optical investigation of thin films containing aluminum and gallium phthalocyanine chlorides is presented. The films were fabricated by Physical Vapor Deposition technique onto quartz substrates and annealed after fabrication in an ambient atmosphere for 24 h at the temperature equal to 150 degrees C or 250 degrees C. The experimental results and theoretical calculation of the Third Harmonic Generation process are reported. The third order nonlinear optical properties are expected and can be more or less accurately predicted due to the assembly of the molecules and theoretical calculations of the frequency-dependent dipole polarizabilities, third hyperpolarizabilities, third order susceptibilities, frontier and second frontier molecular orbitals. These parameters were used to understand the relationship of optical properties with the molecular structures. We found that the annealing process causes formation of nanostructures and the value of the third order optical susceptibility makes these materials interesting for future nonlinear optical applications. (C) 2014 Elsevier Ltd. All rights reserved.Öğe Second and third-order nonlinear optical behavior of natural pigment: chlorophyll and crocin(SPRINGER HEIDELBERG, 2017) Karakas, A.; Karakaya, M.; Taser, M.; Ceylan, Y.; Arof, A. K.; El Kouari, Y.; Sahraoui, B.To provide an insight into the microscopic second and third-order nonlinear optical (NLO) behavior of chlorophyll a and crocin, we have computed the electric dipole moments (mu), dispersion-free first hyperpolarizabilities (beta), frequency-dependent first and second (gamma) hyperpolarizabilities at 1064 nm wavelength area using time-dependent Hartree-Fock (TDHF) method. According to ab-initio calculation results, the examined compounds exhibit first and second hyperpolarizabilities with non-zero values, implying second and third-order NLO phenomena.Öğe Theoretical Calculations of Second and Third-Order Nonlinear Susceptibilities and Their Corresponding Hyperpolarizabilities of a Styrylquinolinium Dye(IEEE, 2014) Karakas, A.; Ceylan, Y.; Bakalska, R.; Todorova, M.; Sofiani, Z.; Sahraoui, B.The second (chi((2))(exp)) and third-order (chi((3))(exp)) susceptibilities of a styrylquinolinium dye (1) have been determined utilizing second-harmonic generation (SHG) and third-harmonic generation (THG) techniques, respectively. The reported measurement findings on chi((2))(exp) and chi((3))(exp) have been compared with the theoretical data evaluated here by means of ab-initio quantum mechanical calculations. The electric dipole moments (mu), static dipole polarizabilities (alpha) and first hyperpolarizabilities (beta) have been computed by density functional theory (DFT) at B3LYP/6-311+G(d, p) level. To reveal the frequency-dependent second and third-order microscopic nonlinear optical (NLO) behavior of the title compound, the dynamic dipole polarizabilities, first and second (gamma) hyperpolarizabilities have been theoretically investigated using time-dependent Hartree-Fock (TDHF) method. According to the experimental and theoretical results, the values of susceptibilities and the corresponding microscopic coefficients with large non-zero responses make the examined dye promising candidate for NLO applications.Öğe Theoretical diagnostics of second and third-order hyperpolarizabilities of several acid derivatives(DE GRUYTER POLAND SP ZOO, 2019) Karakas, A.; Ceylan, Y.; Karakaya, M.; Taser, M.; Terlemez, B. B.; Eren, N.; El Kouari, Y.The density functional theory (DFT) at B3LYP/6-31G(d) level has been utilized to achieve the electric dipole moment (mu), static dipole polarizability (alpha) and first hyperpolarizability (beta) values for ferulic acid (1) and chenodeoxycholic acid (2). The time-dependent Hartree-Fock (TDHF) technique as a powerful quantum chemical method has been implemented to reveal the dynamic alpha, beta and third-order hyperpolarizabilities (gamma) of the examined compounds. Our computational conclusions have been compared with the results of similar materials in the literature. The first and second frontier molecular orbitals (MOs) and their band gaps have also been investigated by means of DFT.Öğe Z-Scan Determination and Ab-Initio Computations on Third-Order Optical Nonlinearities of a Styrylquinolinium Dye(IEEE, 2014) Karakas, A.; Sofiani, Z.; Ceylan, Y.; Taser, M.; Bakalska, R.; Todorova, M.; Sahraoui, B.In order to elucidate the third-order nonlinear optical (NLO) phenomena of the styrylquinolinium dye (1), the nonlinear absorption parameter (beta) and third-order susceptibility (chi((3))) have been measured using the Z-scan measurements. The one-photon absorption (OPA) and two-photon absorption (TPA) characterizations have been determined by configuration interaction (CI) and time-dependent Hartree-Fock (TDHF) methods, respectively. The averaged (isotropic) second hyperpolarizability () allows the determination of the third-order optical response. The ab-initio calculation on with non-zero value reveals that the title dye has relatively good third-order NLO properties. The calculated results of 1 on OPA wavelength, TPA cross-section (delta(omega)) and third-order susceptibility are in reasonable agreement with its experimental data.
