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Öğe Evaluation of Zerumbone as an EGFR Tyrosine Kinase Inhibitor by Molecular Docking Method(University of Ankara, 2023) Yonar, Dilek; Baba, Burcu; Karayel, ArzuObjective: EGFR-TK domain is of great importance in the initiation and progression of various cancer types, especially lung cancer. The existing EGFR-TK inhibitors have numerous side effects, which make them improper to be utilized as cancer therapeutics. In this study, we aimed to analyze the activity of zerumbone as an anticancer agent targeting EGFR by molecular docking approach and to evaluate its activity in comparison with curcumin. Material and Method: MEP and HOMO-LUMO analyses were achieved at B3LYP/6-31G(D,P) level to evaluate electrostatic interactions that affect binding of EGFR with zerumbone and curcumin. Their binding energies were determined by molecular docking and compared with erlotinib as reference ligand. Result and Discussion: Docking studies showed higher bindings (lower binding energy) for curcumin and zerumbone with binding energies -8.0 and -7.6 kcal/mol, respectively, compared to erlotinib (-7.3 kcal/mol). However, there is no significant difference between them. The ?E energy gap of zerumbone was 5.09 eV which implies that this compound has more stability in comparison with curcumin (?E=3.68 eV) and erlotinib (?E=4.29eV). Also, zerumbone showed strong hydrogen bond interactions with EGFR, making it candidate as EGFR inhibitor, as did both in curcumin and erlotinib. It was concluded that zerumbone may have potential for inhibitory activity against EGFRTK.Öğe Revealing the effect of Co/Cu (d7/d9) cationic doping on an electronic acceptor ZnO nanocage surface for the adsorption of citric acid, vinyl alcohol, and sulfamethoxazole ligands: DFT-D3, QTAIM, IGM-NCI, and MD analysis(ELSEVIER SCIENCE SA, 2023) Gassoumi, B.; Mahmoud, A.M. Ahmed; Nasr, S.; Karayel, Arzu; Özkınalı, SevilThe electron-spin duality and propagation of the active sites of free electrons are of interest for adsorbing the guests and fixing them with strong hydrogen bonds (HB). The coherence of the systems with the guests is one of the main parameters that favor the experimentation of new systems on primary column adsorption phenomena. The stability and the adaptable symmetries in all directions justify the use of a “nanocage” (ZnO) for studying adsorption phenomena. The formation of stable electronic charge transfer paths between sites occupied by very stable atomic orbitals ensures the success of the adsorption of the ligands. Electronic characterization (MES, FMO, DOS, and cationic doping) is used to describe the movement of the intra-Cu-Co/Zn19O20 electrons. The phenomena of charge transfer, stability, types of orbital occupations, adsorption sites, electron migration direction, conductivity, and reactivity of such systems are thoroughly explored. Based on these findings, the efficiency of a Cu–Co/Zn19O20 nanocage to adsorb three different ligands (medical ligands, prostate biomarkers, and antibiotics) is studied. From the reactivity parameter discussions, it is found that the copper or cobalt-doped nanocage-Citric Acid has a strongly electronegative index (4.40 eV and 4.91 eV) and hardness (1.99 eV and 1.82 eV) properties. The Fourier transform infrared analyses and orbital localizations (? and ?) clearly demonstrate that the charge transfer occurs inter-surface, from nanocages to adsorbed ligands. Bader’s theory analysis for the adsorption ligands VA (Vinyl Alcohol), CA (Citric Acid), and SMX (Sulfamethoxazole) by the doped copper and cobalt nanocages demonstrates that these systems are much more adequate for adsorbing the ligand antibiotics than the other hosts. The highly adsorbent energy of sulfamethoxazole by Cu–Zn19O20 is equal to ? 582.86 kJ. mol-1. The IGM-NCI/ELF analyses support these findings, revealing that the Cu/Co–Zn19O20 nanocages adsorb SMX via hydrogen bonding and van der Waals interactions, as they also did in DFT-D3 and FT-IR analyses. LOL analyses support this claim by visualizing single-pair spins in excess surrounding acceptor atoms (O) in the two systems. Molecular dynamics simulations show that SMX is quickly adsorbed by nanocages of Zn19O20 doped with copper (d9) or cobalt (d7).Öğe Voltammetric Analysis of Thiram with Bimetallic Nanosensor and Investigation of Adsorption Mechanism by DFT-D3 Method(ELECTROCHEMICAL SOC INC, 2023) Çelik, Murat; Kanbeş Dindar, Çiğdem; Karayel, Arzu; Bozal Palabıyık, Burçin; Uslu, BengiIn this study, to detect thiram electrochemically, a simple nanosensor based on a glassy carbon electrode (GCE) modified with green-synthesized Ag and Au nanoparticles was designed. AuNPs@AgNPs/GCE nanosensor gave considerably greater signal for 5 ppm thiram in pH 3.0 phosphate buffer solution using adsorptive stripping differential pulse voltammetry compared to bare GCE. Under ideal conditions, the nanosensor produced a linear concentration calibration curve extending from 0.2 to 1.4 ppm for thiram, with limits of detection and quantification of 0.033 ppm and 0.100 ppm, respectively. The developed electrochemical bimetallic nanosensor demonstrated high sensitivity and stability, showing that it is a novel and promising platform for thiram determination. Furthermore, the nanosensor was used to assess thiram in human serum and recovery was obtained as 103.6%. DFT-D3 results showed that covalent modification of GCE with AuNPs/AgNPs occurs with the electron transfer between the electrode surface and thiram by bonding sulfur atoms of thiram to AgNPs and AuNPs. Both experimental and theoretical analyses showed that the modification with Ag and Au, GCE appeared to be a key property to improve the electronic activity at the surface and increase the charge transfer that facilitates the adsorption of the selected guest.Öğe Computational Insight into Conformational Rearrangement and Intramolecular-H Bond Analysis of Some Calix[4]Arenes Including Acryloyl Moiety(2019) Karayel, ArzuThe conformational analyses of Calix[4]arenes reveals four different stable structures (conformations); Cone, Partial Cone, 1,2-Alternate and 1,3-Alternate after employing a density functional theory (DFT) computational analysis. Intramolecular Hydrogen Bonds (IHBs) existing Calixarene core cause Cone conformation, supporting to be the best stable state in 1, 2 and 3 compounds. In addition, one needs Natural Bond Orbital (NBO) analyses of current compounds in order to understand nature of these IHBs. Specifically, it has been shown using NBO that the LP *?? interactions for O???O¯H IHBs and the delocalization LP ? ?* for O¯C=O are the major contributions to energy stabilization. Of all conformers of compound 4, Partial Cone has the lowest energy, which can be attributed to devoid of intramolecular hydrogen bond due to the absence of free phenolic groups.Öğe Azo-methoxy-calix[4]arene complexes with metal cations for chemical sensor applications: Characterization, QTAIM analyses and dispersion-corrected DFT- computations(Pergamon-Elsevier Science Ltd, 2022) Gassoumi, B.; Echabaane, M.; Ben Mohamed, F. E.; Nouar, L.; Madi, F.; Karayel, Arzu; Ben Chaabane, R.In this work, the structures, quantum chemical descriptors, morphologic characterization of the azomethoxy-calix[4]arene were investigated. The analyses and interpretation of the theoretical and the experimental IR spectroscopy results for the corresponding compounds was performed. The complexation of the azo-methoxy-calix[4]arene with Zn2+, Hg2+, Cu2+, Co2+, Ni2+, Pb2+ and Cd2+ metal cations has been calculated by the dispersion corrected density functional theory (DFT-D3). The values of the interaction energies show that the specific molecule is more selective to the Cu2+ cation. The study of the reactivity parameters confirms that the azo-methoxy-calix[4]arene molecule is more reactive and sensitive to the Cu2+ cation than that Co2+ and Cd2+. In addition, the investigation of the electrophilic and nucleophilic sites has been studied by the molecular electrostatic potential (MEP) analysis. The Hirshfeld surface (HS) analysis of the azo-methoxy-calix[4]arene-Cu2+ interaction have been used to understand the Cu...hydrogen-bond donors formed between the cation and the specific compound. The Quantum Theory of Atoms in Molecules (QTAIM) via Non covalent Interaction (NCI) analysis was carried out to demonstrate the nature, the type and the strength of the interaction formed between the Cu2+ cation and the two symmetrical ligands and the cavity. Finally, the chemical sensor properties based on the Si/SiO2/Si3N4/Azo-methoxy-calix[4]arene for detection of Cu2+ cation were studied. Sensing performances are determined with a linear range from 10(-5.2) to 10(-2.2) M. The Si/SiO2/Si3N4/azo-methoxy-calix[4]arene structure is a promoter to have a good performance sensor. (C) 2021 Elsevier B.V. All rights reserved.Öğe Effects of Ce-Dy rare earths co-doping on various features of Ni-Co spinel ferrite microspheres prepared via hydrothermal approach(Elsevier, 2021) Almessiere, Munirah Abdullah; Ünal, Bayram; Slimani, Yassine; Güngüneş, Hakan; Toprak, Muhammet S.; Tashkandi, Nabiha; Manikandan, AyyarThe effects of Ce-Dy co-doping on the crystal structure, optical, dielectric, magnetic properties, and hyperfine interactions of Ni-Co spinel ferrite microspheres synthesized hydrothermally have been studied. A series of ferrites with the general formula Ni0.5-Co0.5CexDyxFe2-2xO4 were synthesized with x values ranging from 0.00 to 0.10. The phase, crystallinity, and morphology of ferrite microspheres were analyzed by X-ray powder diffractometry (XRD), scanning and transmission electron microscopes (SEM and TEM), respectively. The structural analyses of the synthesized ferrite microspheres confirmed their high purity and cubic crystalline phase. The Diffuse reflectance spectroscopic (DRS) measurements were presented to calculate direct optical energy band gaps (E-g) and is found in the range 1.63 eV - 1.84 eV. Fe-57 Mossbauer spectroscopy showed that the hyperfine magnetic field of tetrahedral (A) and octahedral (B) sites decreased with the substitution of Dy3+-Ce3+ ions that preferrentially occupy the B site. The impact of the rare-earth content (x) on the magnetic features of the prepared NiCo ferrite microspheres was investigated by analyzing M-H loops, which showed soft ferrimagnetism. The magnetic features illustrate a great impact of the incorporation of Ce3+-Dy3+ ions within the NiCo ferrite structure. The saturation magnetization (M-s), remanence (M-r), and coercivity (H-c) increased gradually with increasing Ce-Dy content. At x = 0.04, M-s, M-r, and H-c attain maximum values of about 31.2 emu/g, 11.5 emu/g, and 512.4 Oe, respectively. The Bohr magneton (n(B)) and magneto-crystalline anisotropy constant (K-eff) were also determined and evaluated with correlation to other magnetic parameters. Further increase in Ce3+-Dy3+ content (i.e., x >= 0.06) was found to decrease M-s, M-r, and H-c values. The variations in magnetic parameters (M-s, M-r, and H-c) were largely caused by the surface spins effect, the variations in crystallite/particle size, the distribution of magnetic ions into the different sublattices, the evolutions of magneto-crystalline anisotropy, and the variations in the magnetic moment (n(B)). The squareness ratios were found to be lower than the predicted theoretical value of 0.5 for various samples, indicating that the prepared Ce-Dy substituted NiCo ferrite microspheres are composed of NPs with single-magnetic domain (SMD). Temperature and frequency-dependent electrical and dielectric measurements have been done to estimate the ac/dc conductivity, dielectric constant, and tangent loss values for all the samples. The ac conductivity measurements confirmed the power-law rules, largely dependent on Ce-Dy content. Impedance analysis stated that the conduction mechanisms in all samples are mainly due to the grains-grain boundaries. The dielectric constant of NiCo ferrite microspheres give rise to normal dielectric distribution, with the frequency depending strongly on the Ce-Dy content. The observed variation in tangential loss with frequency can be attributed to the conduction mechanism in ferrites, like Koop's phenomenological model. (C) 2021 The Author(s). Published by Elsevier B.V.Öğe In silico exploration of O-H center dot center dot center dot X2+ (X = Cu, Ag, Hg) interaction, targeted adsorption zone, charge density iso-surface, O-H proton analysis and topographic parameters theory for calix[6]arene and calix[8]arene as model(Elsevier, 2021) Gassoumi, B.; Ben Mohamed, F. E.; Castro, M. E.; Melendez, F. J.; Karayel, Arzu; Nouar, L.; Ben Ouada, H.In this work, the best adsorption targeted zones of the metal cations Ag2+, Cu2+ and Hg2+ at the surfaces or inside, outside the cavity of the calix[6] (CX[6]), calix[8]arene (CX[8]), NUBMOM (NUB-.) and LAYKUR (LAY-.) have been discussed. For X2+=Ag, Cu and Hg adsorbed onto the surface of CX[6,8], NUB-., and LAY-. and the morphologies of these complexes have been explained, the specific chosen surface structure has interfacial chemical properties to facilitate the stabilization of the cation in each targeted zone. The stability mechanisms have been investigated for the specific systems to understand the role of the cooperativity of the O center dot center dot center dot H (forming a donor-acceptor couple) bonding interactions for good selectivity to the cation in each host-guest in the acetonitrile solvent medium and the gas phase. For this purpose, all the host-guests chemical structures were investigated by the IR spectroscopy and O-H proton approach. The UV-visible absorption spectroscopy and the total DOS Orbital showed that all molecules possess a maximum absorption band in the range between 0.5 and 3.5 eV assigned to pi-pi* or n-pi* transitions, the minimum band is characterized for the CX[6,8]-Cu2+, NUB-.Cu2+ and LAY-.Cu2+, while the highest band is specified for the complexation with the cation Ag2+. The Hirshfeld surface and the molecular electrostatic potential topography have demonstrated the selected targeted zone for the most stable configurations. The nature and the type of interaction formed between the chosen cation and the targeted area of the CX[6,8], NUB-. and LAY-. were typically studied by the Atom in Molecules (AIM) approach via non-covalent interaction (NCI) analyses. According to theoretical calculations, Cu2+, Ag2+ and Hg2+ cations were complexed with CX[6] and CX [8]-arenes in endo and exo-type form. In the endo complexes, it has been observed that Cu2+ and Ag2+ cations enter the lower rim space where calixarene hydroxyl groups are located and form a complex in square planer geometry, as expected. This situation shows that the copper cation is planarly located in the calixarene core. These results show that the theoretical results are in good agreement with the experimental ones. In addition, our simulations point out the calix[6] arene and calix[8]arene were complexed with cations by pinched conformation, corresponding to best stable state. (C) 2021 Elsevier B.V. All rights reserved.Öğe Influence of Dy3+ Ions on the Microstructures and Magnetic, Electrical, and Microwave Properties of [Ni0.4Cu0.2Zn0.4](Fe2-xDyx)O-4 (0.00 <= x <= 0.04) Spinel Ferrites(Amer Chemical Soc, 2021) Almessiere, Munirah Abdullah; Slimani, Yassine; Güngüneş, Hakan; Demir Korkmaz, Ayşe; Zubar, Tatiana; Trukhanov, Sergei; Baykal, Abdulhadi[Ni0.4Cu0.2Zn0.4](Fe2-xDyx)O-4 spinel ferrite nanoparticles with different Dy3+ concentrations (0.00 <= x <= 0.04) were prepared by a citrate sol-gel auto-combustion technique. A strong correlation among Dy concentration, structural parameters, and magnetic, electrical, and microwave properties was established. An increase in the Dy3+ concentration is the reason for a rise in the crystal structure parameters (due to different ionic radii of Fe and Dy ions) and a slight increase in the average particle size with a minor reduction in the specific surface area. It was observed that Dy3+ ions prefer to occupy the octahedral B site due to their large ionic radius (0.91 A). The explanation of the electrical and magnetic properties was given in terms of the features of Dy3+-O2--Fe3+ dysprosium-oxygen-iron indirect exchange. The occurrence of the intensive changes in amplitude-frequency characteristics was observed from 1.6 to 2.7 GHz. The explanation of electromagnetic absorption was given in terms of the peculiarities of the microstructure (resonance of domain boundaries). The results open perspectives in the utilization of [Ni0.4Cu0.2Zn0.4](Fe2-xDyx)O-4 spinel ferrite nanoparticles as functional materials for targeted drug delivery and hyperthermia applications.Öğe Correlation between chemical composition, electrical, magnetic and microwave properties in Dy-substituted Ni-Cu-Zn ferrites(Elsevier, 2021) Almessiere, Munirah Abdullah; Slimani, Yassine; Güngüneş, Hakan; Demir Korkmaz, Ayşe; Trukhanov, Sergei V.; Güner, Sadık; Baykal, AbdulhadiDy3+ ion-substituted nanoferrites Ni0.4Cu0.2Zn0.4Fe2_ xDyxO4 (x <= 0.04) were produced via sol-gel method. Correlation between chemical composition, crystal structure, electrical, magnetic and microwave properties was investigated. All samples were characterized by single-phase state. It was observed that the increase of the Dy content leads to a decrease in the average crystallite size. The bandgap (Eg) was deduced to be between 1.83 and 1.86 eV. The measurements of magnetization versus applied magnetic field (M-H) and magnetization versus temperature (M-T) were investigated by vibrating sample magnetometer (VSM). Magnetic measurements revealed superparamagnetic character at room temperature. The magnetization was increased initially with doping Dy3+ in the ratio of x = 0.01 compering to the un-doped sample and thereafter dropped as Dy3+ ions content further increases. Microwave properties were discussed in terms of electromagnetic absorption in the frequency range 1-20 GHz. The occurrences of the intensive electromagnetic absorption in the frequency ranged from 1.6 to 2.7 GHz were observed. The changes in the amplitude-frequency characteristics correlated well with the level of chemical substitution (x) with Dy ions concentration.Öğe Theoretical assessment of calix[4]arene-N-beta-ketoimine (n=1-4) derivatives: Conformational studies, optoelectronic, and sensing of Cu(2+)cation(Springer, 2021) Gassoumi, B.; Ben Mohamed, F. E.; Khedmi, N.; Karayel, Arzu; Echabaane, M.; Ghalla, H.; Ben Chaabane, R.Herein, we have investigated the key functions of the calix[4]arene, abbreviated as CX [1], and designed its several derivatives by substitution of the functional groups. Molecular geometry provides an intuitive understanding of the effect of functional groups on various physical properties. The addition of the N-beta -ketoimine (n=1-4) ligands has a direct effect on the stretching vibration of the H-bonding interaction. The results showed that all molecules possess absorption bands at 190 nm and in the range between 200 and 300 nm assigned to pi-pi* and n-pi* transitions. HOMO-LUMO energy gap of the CX[4]-N-beta -ketoimine, one with chemical hardness of 1.62 eV, has been found to be 3.24 eV calculated at B3LYP/6-31+G(d) level of theory. This finding explains the good kinetic stability of this compound. The large values of electrophilicity make the current molecules as a good electrophilic species. The atom in molecule (AIM) and the reduced density gradient (RDG) analyses showed the type and the strength of the interactions taking place between Cu2+ and the beta -ketoimine ligands.Öğe Structural, Magnetic, and Mossbauer Parameters' Evaluation of Sonochemically Synthesized Rare Earth Er3+ and Y3+ Ions-Substituted Manganese-Zinc Nanospinel Ferrites(Amer Chemical Soc, 2021) Almessiere, Munirah Abdullah; Güner, Sadık; Güngüneş, Hakan; Sertkol, Murat; Slimani, Yassine; Badar, Rabail; Baykal, AbdulhadiThe effect of Er3+ and Y3+ ion-co-substituted Mn0.5Zn0.5ErxYxFe2-2xO4 (MZErYF) (x <= 0.10) spinel nanoferrites (SNFs) prepared by a sonochemical approach was investigated. Surface and phase analyses were carried out using SEM, TEM, and XRD. Hyperfine parameters were determined by fitting room-temperature (RT) Mossbauer spectra. Magnetic field-dependent magnetization data unveiled the superparamagnetic nature at RT and ferrimagnetic nature at 10 K. RT saturation magnetization (M-S) and calculated magnetic moments (n(B)) are 34.84 emu/g and 1.47 mu(B), respectively, and have indirect proportionalities with increasing ion content. M-S and n(B) data have a similar trend at 10 K including remanent magnetizations (M-r). The measured coercivities (H-C) are between 250 and 415 Oe. The calculated squareness ratios are in the range of 0.152-0.321 for NPs and assign the multidomain nature for NPs at 10 K. The extracted effective magnetocrystalline constants (K-eff) have an order of 104 erg/g except for Mn0.5Zn0.5Er0.10Y0.10Fe1.80O4 SNFs that has 3.37 x 10(5) erg/g. This sample exhibits the greatest magnetic hardness with the largest magnitude of H-C = 415 Oe and an internal anisotropy field H-a = 1288 Oe among all magnetically soft NPs.Öğe Effect of atomic-layer-deposited HfO2 thin-film interfacial layer on the electrical properties of Au/Ti/n-GaAs Schottky diode(Springer, 2021) Yıldız, Dilber Esra; Karabulut, Abdülkerim; Orak, Iman; Türüt, AbdulmecitThe electrical properties of Au/Ti/HfO2/n-GaAs metal/insulating layer/semiconductor (MIS) contact structures were analyzed in detail by the help of capacitance-voltage (C-V) and conductance-voltage (G-V) measurements in the temperature range of 60-320 K. The HfO2 thin-film layer was obtained by atomic layer deposition technique (ALD). The main electrical parameters such as ideality factor (n) and barrier height (Phi(B0)) were determined for Au/Ti/n-GaAs and Au/Ti/HfO2/n-GaAs diodes using current-voltage (I-V) measurement at 300 K. The values of these parameters are 1.07 and 0.77 eV for the reference (Au/Ti/n-GaAs) diode and 1.30 and 0.94 eV for the Au/Ti/HfO2/n-GaAs MIS diode, respectively. An interfacial charge density value of Q(ss) = 4.14 x 10(12) Ccm(-2) for the MIS diode was calculated from the barrier height difference of Delta Phi = 0.94 - 0.77 = 0.17V. Depending on these results, the temperature-dependent C-V and G-V plots of the device were also investigated. The series resistance (R-s), phase angle, the interface state density (D-it), the real impedance (Z') and imaginary impedance (Z '') were evaluated using admittance measurements. The C and G values increased, whereas (Z '') and Z decreased with increasing voltage at each temperature. An intersection point being independent of temperature in the G-V curves appeared at forward-bias side (approximate to 1.4 V); after this intersection point of the G-V plot, the G values decreased with increasing temperature at a given voltage. The intersection points in total Z versus V curves appeared at forward-bias side (approximate to 1.7 V). The Nyquist spectra were recorded for the MIS structure showing single semicircular arcs with different diameters depending on temperature.Öğe Dielectric characterization of Al/PCBM:ZnO/p-Si structures for wide-range frequency(Indian Acad Sciences, 2021) Yıldız, Dilber Esra; Koçyiğit, Adem; Erdal, Mehmet Okan; Yıldırım, MuratThe dielectric properties of the Al/PCBM:ZnO/p-Si structure were investigated using the impedance spectroscopy technique. PCBM:ZnO layer was obtained by spin coating method on the p-Si. The morphological properties of the PCBM:ZnO were investigated using atomic force microscopy. The results highlighted that PCBM:ZnO thin film has uniform surfaces. The dielectric parameters such as real and imaginary parts of the electric modulus (M ' and M '') and ac electrical conductivity (sigma), dielectric constant (epsilon '), dielectric loss (epsilon ''), loss tangent (tan delta) values were determined. The results of the dielectric properties of the Al/PCBM:ZnO/p-Si structures impressed voltage and frequency changing. The Al/PCBM:ZnO/p-Si structures can be regarded as a candidate for organic diode applications.Öğe A study on electrical properties of Au/4H-SiC Schottky diode under illumination(Springer, 2021) Yıldız, Dilber Esra; Karadeniz, S.; Güllü, Hasan HüseyinY In this work, a metal-semiconductor diode in the form of Au/4H-SiC is fabricated, and the electrical properties of this device are systematically examined under dark and different illumination intensities. To perform this, the currentvoltage (I-V) characteristics of the Schottky-type diode are analyzed at room temperature. The performance parameters such as saturation current (I-0), barrier height (Phi(B)), ideality factor (n) and series resistance (R-s) are found to be illumination dependent. The reverse biased I - V characteristics under incident light indicate high photo-sensitivity as compared to the response at forward bias. Thus, this result is investigated in detail according to both Schottky and Poole-Frenkel effects. It is found that the Poole-Frenkel mechanism is dominant in the reverse biased region. The Au/4H-SiC Schottky junction has a strong photo-current response to the different illumination intensities and transient photocurrent characteristics of the fabricated device are studied at the illumination intensities of 50 and 100 mW/cm(2). All experimental results indicate that the Au/4H-SiC Schottky diode, with a valuable response to the illumination together with change in illumination intensity, can be used for optoelectronic applications.Öğe Impact of Gd substitution on the structure, hyperfine interactions, and magnetic properties of Sr hexaferrites(Elsevier Sci Ltd, 2021) Almessiere, Munirah Abdullah; Slimani, Yassine; Sertkol, Mehriye; Güngüneş, Hakan; Wudil, Yakubu Sani; Demir Korkmaz, Ayşe; Baykal, AbdulhadiGd3+-substituted nano-sized Sr-hexaferrite, SrGd(x)Fe(12-x)O19 (0.00 <= x <= 0.05) NHFs (SrGd NHFs), were fabricated by a one-pot sol-gel combustion approach assisted by citric acid. The crystal structures, surface morphologies, magnetic properties, and hyperfine interactions of the calcined samples were characterized by X-ray diffraction (XRD), scanning electron microscopy (SEM), X-ray photoelectron spectroscopy (XPS), energy-dispersive X-ray spectroscopy (EDX), high-resolution TEM (HR-TEM), vibrating sample magnetometry (VSM), and Mossbauer spectrometry. The oxidation states and chemical compositions of the NHFs were evaluated using XPS. The single-phase crystalline structures of all products were confirmed by XRD analysis. The average crystallite sizes determined from the peaks of the highest intensity using the Scherrer equation were between 38 and 50 nm. Using 57Fe Mossbauer spectroscopy data, the quadrupole splitting, hyperfine magnetic field, isomer shift, and line width variation of the products were determined. The Mossbauer spectra showed that octahedral (O-h) 12k and 2a sites were preferentially occupied by Gd3+ ions. The Gd3+ content was found to have no influence on the electron density around the Fe3+ ions at any crystallographic site. The magnetization (M) versus magnetic field (H) data were collected at room (300 K) and ultra-low (10 K) temperatures. Neither the zero-field cooling (ZFC) nor field cooling (FC) mode plots of magnetization vs. temperature revealed any blocking temperature peaks. Both the M H curves and FC-ZFC magnetization revealed ferrimagnetic behavior of the products. Furthermore, the FC-ZFC magnetization exhibited super-spin glass behavior at low temperatures. Reductions in the coercive field (H-c), saturation magnetization (M-s), and remanence (M-r) magnetization were achieved with Gd substitution of up to 0.03 into the hexaferrite system; however, with further increase in Gd content, these values started to increase. The calculated squareness ratio (M-r/M-s) revealed that all of the NHF samples were composed of single magnetic domain particles with uniaxial anisotropy.Öğe Analysis of Double Gaussian Distribution on Barrier Inhomogeneity in a Au/n-4H SiC Schottky Diode(Springer, 2021) Güllü, Hasan Hüseyin; Şeme Şirin, Dilara; Yıldız, Dilber EsraA n-4H SiC based diode is fabricated by an Au front metal contact to provide rectification at the metal-semiconductor (MS) junction, and a back ohmic contact is also obtained using Au metal with post-thermal heating. MS diode characteristics are investigated by current-voltage (I - V) measurements with a wide range of temperature from 80 K to 300 K. At each temperature, rectifying behavior is achieved and it is improved with an increase in temperature. Barrier height and ideality factor are calculated according to the thermionic emission (TE) model from linearity in the forward bias region of the ln(I) versus V plot. The experimental zero-bias barrier height (Phi(b0)) values are in a good agreement with literature, and at around room temperature the ideality factor (n) reaches unity. At saturation regions in I - V curves, parasitic resistance values are derived by Ohm's law and the series resistance values are also reevaluated by Cheung's relation. Detailed I - V analysis is performed by modifying the TE model with an approximation of low barrier patches embedded in the main barrier height. Two linear relations in the characteristic plots of Phi(b0) and n indicate that double Gaussian distribution is a suitable current conduction model via localized barrier patches at low temperatures. Additionally, reverse bias current flow is analyzed under the dominant effect of Poole-Frenkel emission associated with the interfacial traps. According to the characteristic electric field-dependent current density plot, emission barrier height and relative dielectric constant for n-4H SiC are calculated.Öğe SYNTHESIS, CHARACTERIZATION, THERMAL, X-RAY, AND DFT ANALYSES OF 6-TERT-BUTYL 3-ETHYL 2-[(3-METHOXY/5-BROMO)-2-HYDROXY AND (3-NITRO/3-METHOXY)BENZYLIDENEAMINO]- 4,5-DIHYDROTHIENO[2,3-C]PYRIDINE-3,6(7H)-DICARBOXYLATE(Pleiades Publishing Inc, 2021) Çolak, Naki; Karayel, Arzu; Buldurun, Kenan; Turan, NevinIn this work, 6-tert-butyl 3-ethyl 2-amino-4,5-dihydrothieno[2,3-c]pyridine-3,6(7H)-dicarboxylate is synthesized from starting tert-butyl 4-oxopiperidine-1-carboxylate, ethyl cyanomalonate, and sulfur, and then, coupled with same aromatic aldehyde affords the corresponding Schiff base compounds. These compounds (2a-d) are characterized using FTIR, H-1 and C-13 NMR spectroscopic methods. The crystal and molecular structure of (E)-6-tert-butyl 3-ethyl 2-((2-hydroxy-3-methoxybenzylidene)amino)-4,5-dihydrothieno[2,3-c]pyridine-3,6(7H)-dicarboxylate (2a) is characterized by the X-ray crystallographic analysis. Compound 2a crystallizes in the monoclinic space group P2(1)/c. The molecular and crystal structure is stabilized by two O-HMIDLINE HORIZONTAL ELLIPSISN and O-HMIDLINE HORIZONTAL ELLIPSISO intramolecular hydrogen bonds (OMIDLINE HORIZONTAL ELLIPSISN and OMIDLINE HORIZONTAL ELLIPSISO are 2.598(5) angstrom and 2.990(5) angstrom, respectively; O-HMIDLINE HORIZONTAL ELLIPSISN = 147 degrees and O-HMIDLINE HORIZONTAL ELLIPSISO = 134 degrees). According to DFT, compound 2d also shows the intramolecular hydrogen bonding, while there is no this type of interaction in compound 2b and 2c.Öğe Molecular stabilities, conformational analyses and molecular docking studies of benzimidazole derivatives bearing 1,2,4-triazole as EGFR inhibitors(Springer/Plenum Publishers, 2021) Karayel, ArzuA detailed study of the tautomeric properties, the conformations, and the mechanism behind the anti-cancer properties of 5-{[2-(4-methoxyphenyl)-1H-benzimidazol-1-yl]methyl}-4-ethyl-2,4-dihydro-3H-1,2,4-triazole-3-thione (1), 2-(4-chlorophenyl) (2), 2-phenyl (3), 2-(3,4-dibenzyloxyphenyl) (4), and 2-(4-methoxyphenyl); 4-[2-(piperidin-1-yl)ethyl] (5) has been conducted using density functional theory and molecular docking. The most stable states of all the structures are shown to be in the thione form. The scans of the compounds point out two conformers at PES, one of two conformers for molecule 1 corresponds to X-ray geometry, being the lowest energy state. Current molecules (1, 2, 3, and 5) have one inter-molecular hydrogen bond between NH atom of triazole ring and =O atom in residue ARG817 of the EGFR binding pocket, while compound 4 has different type inter-molecular hydrogen bond which is between N atom in benzimidazole ring and H atom of NH3 in residue LYS721. Off all hydrogen bonds, that of 5 is the strongest one with 2.26 angstrom. Compound 4 has shown the best binding affinity with -10.0 kcal/mol. This compound is the most active compound regarding to the potential anti-cancer activity.Öğe SrCoxZrxFe12-2xO19 and SrNixZrxFe12-2xO19 hexaferrites: A Comparison Study of AC Susceptibility, FC-ZFC and hyperfine interactions(Elsevier, 2020) Almessiere, Munirah Abdullah; Slimani, Yassine; Güngüneş, Hakan; Demir Korkmaz, Ayşe; Baykal, Abdulhadi; Trukhanov, An V.; Yasin, GhulamThis study compares the AC susceptibility, FC-ZFC and hyperfine interactions of Sr(CoxZrx) Fe12-2xO19 and Sr(NixZrx)Fe12-2xO19 hexaferrites (HFs) manufactured via ultrasonic route. The formation of M-type hexaferrites have been confirmed by X-ray powder diffraction (XRD), Fourier transform-infrared spectroscopy (FT-IR) and high-resolution transmission electron microscopy (HR-TEM) techniques. Scanning electron microscopy (SEM) presented the hexagonal-platelet morphology of products. The variation in isomer shift, line width, quadrupole splitting and hyperfine magnetic field values of them have been governed by Fe-57 Mossbauer spectroscopy which showed that Co2+ and Zr4+ ions located at generally octahedral and 2b sites, while Ni2+ and Zr4+ ions located at octahedral 12k and 4f(2) sites. Measurements of magnetization versus temperature (M-T) and AC susceptibility versus temperature were carried out. The various synthesized HFs displayed ferrimagnetic behavior in the temperature interval of 10-325 K. Super-spin glass-like behavior was noticed at lower temperatures. Neel-Arrhenius and Vogel-Fulcher models were used to explore the experimental AC susceptibility. It was showed that a lower Co-Zr substitution content leads to strengthen the magnetic exchange interactions, however even low Ni-Zr substitution content provoke a reduction in magnetic exchange interactions.Öğe Ultrasonic synthesis, magnetic and optical characterization of Tm(3+)and Tb3+ ions co-doped barium nanohexaferrites(Academic Press Inc Elsevier Science, 2020) Almessiere, Munirah Abdullah; Slimani, Yassine; Güner, Sadık; Aldakhil, Sadal Khalid; Demir Korkmaz, Ayşe; Sertkol, Murat; Baykal, AbdulhadiThis study investigated the structural, optical and magnetic properties of BaTmxTbxFe12-2xO19(x <= 0.05) nanohexaferrites (NHFs) produced by ultrasonic assisted sol-gel combustion approach. The structure of all samples was characterized through XRD powder pattern, SEM, TEM and HR-TEM. UV-Vis diffuse reflectance studies specify that direct band gap (E-g) of pristine BaFe12O19 increases from 1.86 eV to maximum 2.55 eV due to ion substitution. The field dependent magnetization G(H) loops a 300 and 10 K were registered by applying a dc magnetic field up to +/- 10 kOe. Substitutions of Fe3+ ions by Tm3+ and Tb3+ ions affect remarkably the magnetic parameters of samples. Measured remnant magnetizations (sigma(r)) and coercivity fields (H-c) are in a range of 25.60-32.88 emu/g and 2116-4334 Oe, respectively at RT. On the other hand, estimated RT saturation magnetizations (sigma(s)) are in a range of 44.30-58.31 emu/g, and magneton numbers (n(B)) are between 8.83 and 11.72 mu(B). Magnetic parameters at 10 K have much greater magnitudes as sigma(s) = 65.11-94,12 emu/g, sigma(r) = 32.50-47.75 emu/g, n(B) = 12.96-18.91 mu(B). Coercive fields sharply decreased to a range of 720-2068 Oe at 10 K. All samples exhibit strong ferromagnetic features at both temperatures. The observed magnetic features assign that the ultrasonically produced NPs hexaferrites are suitable materials for high-density recording media and permanent magnets.
