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Öğe Synthesis, crystal structure, DFT studies, Hirshfeld surface analysis and drug delivery performance of bis(2-chloro-4,6-diaminopyrimidine)copper(II)-dichloride(Elsevier, 2021) Yağcı, Nermin Kahveci; Kansız, Sevgi; Özcandan, EdaThe new single crystal, bis(2-chloro-4,6-diaminopyrimidine)-copper(II)-dichloride [CDPCD] compound was synthesized. The crystal structure of the compound was solved by the single crystal X-ray diffraction method. CDPCD has a = 6.3334(9) angstrom, b = 6.9914 (10) angstrom, c = 8.9901(12) angstrom, alpha = 78.127(11) degrees, beta = 86.853(11) degrees, gamma = 67.307(10)degrees and Z = 1 parameters and is crystallized in the space group P-1 in the triclinic crystal system. Complete vibration assignments of CDPCD in gas phase and experimental frequencies are reported together with the scaled force constants. The optimized geometric parameters and frequency values were theoretically calculated using DFT/B3LYP method with LANL2DZ basis set. The XRD single crystal measurement parameters are good agreed with the optimized parameters. Molecular orbital surfaces and molecular electrostatic potential properties were measured at B3LYP/LANL2DZ level. Hirshfeld surface and fingerprint drawings were obtained to explain the intermolecular interactions of the crystal structure. The most important contributions for the crystal packing are from Cl center dot center dot center dot H/H center dot center dot center dot Cl (38.7%), H center dot center dot center dot H (17.9%) and N center dot center dot center dot H/H center dot center dot center dot N (14.8%) interactions. In addition, the molecule was tested by MTT test to determine the apoptosis and necrosis by cytotoxicity and double staining method. For the MTT test [MTT: (3,4,5-dimethylthiazol-2-yl)-2,5-diphenyltetrazolium bromide], the tetrazolium salt was used. In different percentages of the compound, apoptotic necrotic index ratios of L929 fibroblasts and MCF-7 cells decreased. Bilateral staining method was used to evaluate the cells that had undergone apoptosis and necrosis of FITC (480-520nm wavelength). Apoptotic and necrotic index results of L929 fibroblasts and MCF-7 cells decreased as the amount of concentration decreased. (C) 2021 Elsevier B.V. All rights reserved.Öğe Synthesis, crystal structure, antibacterial activity and theoretical studies on a novel Zn(II) complex based on 2,4,6-tris(2-pyridyl)-1,3,5-triazine ligand(Elsevier, 2021) Güven, Gamze Bakır; Çınarlı, Murat; Sas, Emine Babur; İdil, Önder; Yagci, Nermin KahveciIt is known that 2,4,6-tri(2-pyridyl)-1,3,5-triazine (tptz) also belongs to noticeable building blocks in both organic and inorganic supramolecular chemistry. We have prepared new Zn(II) complex of 2,4,6-tri(2-pyridyl)-1,3,5-triazine. The new metal complex was characterized by elemental analysis, IR spectra, UV spectra measurements. The molecular structure of [Zn(tptz)(Cl)(2)] was investigated by X-Ray single crystal technique. From all data, the stoichiometry of the complex was found to be 1:1 (metal/ligand). The all data indicated that the tptz exhibits major coordination site behavior. Potential energy surface (PES) was calculated using the DFT / B3LYP / 6-311 G (d, p) method to determine the lowest energy state of the molecular structure. Geometric structure parameters and vibration wavenumbers calculated according to the lowest energy state were compared with experimental data. The electronic properties such as frontier molecular orbital analysis and Uv-Vis spectrum obtained at acetonitrile solvent and gas phase were also studied.). The [Zn(tptz)(Cl)(2)] complex was screened for antibacterial activity against Gram-positive, Gram-negative and yeast by using minimal inhibitory concentration method (MIC). [Zn(tptz)(Cl)(2)] has been found to show significant antimicrobial effects on gram (-), gram (+) and eukaryotic yeast. The DNA binding interactions was also determined experimentally by spectrophotometric and electrochemical methods. (C) 2021 Published by Elsevier B.V.Öğe Strain engineering of electronic and optical properties of monolayer diboron dinitride(Amer Physical Soc, 2021) Demirci, Salih; Rad, Soheil Ershad; Jahangirov, SeymurWe studied the effect of strain engineering on the electronic, structural, mechanical, and optical properties of orthorhombic diboron dinitride (o-B2N2) through first-principles calculations. The 1.7-eV direct band gap observed in the unstrained o-B2N2 can be tuned up to 3 eV or down to 1 eV by applying 12% tensile strain in armchair and zigzag directions, respectively. Ultimate strain values of o-B2N2 were found to be comparable with that of graphene. Our calculations revealed that the partial alignment of the band edges with the redox potentials of water in pristine o-B2N2 can be tuned into a full alignment under the armchair and biaxial tensile strains. The anisotropic charge carrier mobility found in o-B2N2 prolongs the average lifetime of the carrier drift, creating a suitable condition for photoinduced catalytic reactions on its surface. Finally, we found that even in extreme straining regimes, the highly anisotropic optical absorption of o-B2N2 with strong absorption in the visible range is preserved. Having strong visible light absorption and prolonged carrier migration time, we propose that strain engineering is an effective route to tune the band gap energy and band alignment of o-B2N2 and turn this two-dimensional material into a promising photocatalyst for efficient hydrogen production from water splitting.Öğe Stability and electronic properties of monolayer and multilayer structures of group-IV elements and compounds of complementary groups in biphenylene network(Amer Physical Soc, 2022) Demirci, Salih; Çallıoğlu, Şafak; Gorkan, Taylan; Aktürk, Ethem; Çıracı, SalimWe predict that specific group-IV elements and IV-IV, III-V, and II-VI compounds can form stable, free-standing two-dimensional (2D) monolayers consisting of octagon, hexagon, and square rings (ohs), in which the threefold coordination of atoms is preserved to allow sp(2)-type hybridization. These monolayers can also construct bilayers, multilayers, three-dimensional (3D) layered van der Waals solids, and 3D crystals with strong vertical bonds between layers as well as quasi-one-dimensional nanotubes and nanoribbons with diverse edge geometries. All these ohs structures can constitute a large class of 2D materials ranging from good metals to wide bandgap semiconductors and display physical and chemical properties rather different from those of their counterparts in the hexagonal (honeycomb) network. The metallic state of freestanding 2D C, Si, and Ge ohs monolayers and 3D C ohs bulk contrast, respectively, with graphene, silicene, germanene, and graphite.Öğe Spin Induced Quantum Tunneling of the Magnetization(World Scientific Publ Co Pte Ltd, 2021) Yıldız, Gökçen Dikici; Yıldız, Yasin Göktürk; Sarli, NumanQuantum tunneling of the magnetization (QTM) of the spin-1/2 Vanadium-15 (V15) single molecular magnets (SMMs) is investigated by means of the effective field theory developed by Kaneyoshi. We deal with the two hexagon layers (shell, VS) and one triangular interlayer (core, VC) with the spin-1/2 Ising particles. We find that the V15 has a normal ferromagnetic hysteresis behavior for its all spins are up (parallel). However, V15 has a staircase-like hysteresis behavior that is the signature of the QTM for the spin-down orientation (antiparallel) of the core. QTM appears with the splitting of the magnetizations versus temperature (M-T) and external field (M-H) curves. Namely, QTM occurs from +m(VC1) to -m(VC2)(|m(VC1)|>|m(VC2)|) in the core, from +m(VS1) to +m(VS2) (|m(VS1)|>|m(VS2)|) in the shell (only mVS-H curves at T> 0.1) and from +M1(V15) to +M2(V15) (|M1V15|>|M2V15|) in the total V15. By considering these different splitting behaviors of the magnetizations of the shell, core and total V15 at TT-C, we suggest three different kinds of QTM: 1-ferromagnetic QTM (FMQTM) at TT-C for the shell, core and total V15 SMM. Moreover, it is found that there is a relationship between the QTM and type II and surface superconductivity. The EFT results of QTM in V15 are in good agreement with the other theoretical and experimental results of the V15 and other SMMs.Öğe Spectral analysis and biological activity assessment of silver doped hydroxyapatite(Taylor & Francis Ltd, 2021) Erdem, Ümit; Bozer, Büşra Moran; Turkoz, Mustafa B.; Metin, Ayşegül Ülkü; Yıldırım, Gürcan; Türk, Mustafa; Nezir, SaffetIn this study, the hydroxyapatite biomaterials are produced by the precipitation method and the role of silver doping within the different molar ratios of 2.0, 5.0, and 10.0% are investigated with some fundamental analysis, including powder XRD, SEM, EDS, FTIR, Raman, and material densities. In vitro biocompatibility assessment is conducted with cytotoxicity and agar diffusion tests. Moreover, genotoxicity tests determine whether the biomaterials produced cause the mutations or not. In addition, a hemolytic effect test examines the variation of hemolytic behavior of compounds. Also, the cell migration experiments inspect the influence of silver ion levels in biomaterials on many biological processes. The experimental results reveal that the honeycomb-patterned morphological structures are obtained for all the products. FTIR and Raman analyses reveal that the dramatic changes in the characteristic functional group peaks are obtained with the increment in the amount of silver ions. The experimental parts related to the biocompatibility assessment of the study show that there seems to be deterioration in biocompatibility as the silver ion-doping level increases in the system. To sum up, the ideal doping value for bone tissue engineering applications is found to be 2%.Öğe Review of Shape Phase Transition Studies for Bose-Fermi Systems: The Effect of the Odd-Particle on the Bosonic Core(Mdpi, 2021) Böyükata, Mahmut; Alonso, C. E.; Arias, Jose M.; Fortunato, Lorenzo; Vitturi, A.The quantum phase transition studies we have done during the last few years for odd-even systems are reviewed. The focus is on the quantum shape phase transition in Bose-Fermi systems. They are studied within the Interacting Boson-Fermion Model (IBFM). The geometry is included in this model by using the intrinsic frame formalism based on the concept of coherent states. First, the critical point symmetries E(5/4) and E(5/12) are summarized. E(5/4) describes the case of a single j = 3/2 particle coupled to a bosonic core that undergoes a transition from spherical to gamma-unstable. E(5/12) is an extension of E(5/4) that describes the multi-j case (j = 1/2,3/2,5/2) along the same transitional path. Both, E(5/4) and E(5/12), are formulated in a geometrical context using the Bohr Hamiltonian. Similar situations can be studied within the IBFM considering the transitional path from U-BF(5) to O-BF(6). Such studies are also presented. No critical points have been proposed for other paths in odd-even systems as, for instance, the transition from spherical to axially deformed shapes. However, the study of such shape phase transition can be done easily within the IBFM considering the path from U-BF(5) (spherical) to SUBF(3) (axial deformed). Thus, in a second part, this study is presented for the multi-j case. Energy levels and potential energy surfaces obtained within the intrinsic frame formalism of the IBFM Hamiltonian are discussed. Finally, our recent works within the IBFM for a single-j fermion coupled to a bosonic core that performs different shape phase transitional paths are reviewed. All significant paths in the model space are studied: from spherical to gamma-unstable shape, from spherical to axially deformed (prolate and oblate) shapes, and from prolate to oblate shape passing through the gamma-unstable shape. The aim of these applications is to understand the effect of the coupled fermion on the core when moving along a given transitional path and how the coupled fermion modifies the bosonic core around the critical points.Öğe Refinement of fundamental characteristic properties with homovalent Er/Y partial replacement of YBa2Cu3O7-y ceramic matrix(Elsevier Science Sa, 2021) Erdem, Ümit; Turkoz, Mustafa B.; Yıldırım, Gürcan; Zalaoğlu, Yusuf; Nezir, SaffetIn the current work, the effect of partial substitution of Er-sites for the Y-sites in the bulk YBa2Cu3O7-y (YBCO) crystal system on the fundamental superconducting, electrical, crystallinity and structural morphology features is examined together with the reasons by means of powder X-ray diffraction (XRD), temperature-dependent electrical resistivity (rho-T), scanning electron microscopy (SEM), electron dispersive X-ray (EDX) investigations and deduced calculation parameters. All the experimental test results show that the erbium impurities are suc-cessfully substituted by the yttrium sites in the bulk Y-123 crystal system, confirmed by sensitively the EDX and rho-T measurement results. Moreover, it is found that all the fundamental characteristic quantities improve with the increment in the Er/Y partial substitution level up to the value of x = 0.03 beyond which the features tend to degrade dramatically. In this respect, the bulk Y1-xErxBa2Cu3O7-y ceramic compound prepared within the molar ratio of x = 0.03 crystallizes in the orthorhombic space group P-4/ mmm with a little distortion due to the refinement in the crystallinity quality, crystallite growth, oxygen ordering degree, scattering mechanism, intra and intergrain boundary couplings, grain alignment distributions and orientations. The XRD results show that the optimum erbium content enables to develop seriously the fundamental crystallographic features (lattice strain, lattice cell constants, crystallite size distribution, dislocation density ratio, oxygen concentrations in the unit cells) of Y-123 crystal structure. However, the excess Er/Y substitution leads to enhance considerably the systematic structural problems and inhomogeneous distribution of strains (formed by the structural defects) in the YBCO crystal structure. Thus, the phase transition from orthorhombic to tetragonal (structural O-T transition) crystal structure is observed. In fact, the XRD result displays that the trivalent Er3+ particles may partially be replaced by the divalent Cu2+ host atoms in the bulk Y-123 crystal structure after the critic substitution level of x = 0.03. The optimum Er concentration causes to form more thermodynamically activated super-electrons in the homogeneous superconducting cluster percentages in the paths due to the induced polaronic effect, and accordingly the intrinsic overdoped nature of Y-123 ceramic system transits into optimally doped state. Similarly, the erbium ions enable to increase the mobile hole carrier concentration and homogeneities in the oxidation state of superconducting grains. Namely, the amplitude of pair wave function (Psi=Psi(0)e(-i phi)) is strength enough to form bipolarons in the polarizable lattices and localize of densities of electronic states (DOS) at Fermi level. SEM investigations picture that the surface morphology view and crystallinity quality develop remarkably with the increment in the erbium content up to the critical dopant level of x = 0.03 where the sample exhibits the best grain alignment orientations, densest and smoothest surface morphology with the combination of lowest porous and largest particle distributions well linked each other. All in all, this comprehensive work based on the analysis of Er/Y partial replacement mechanism along the YBa2Cu3O7- y ceramic matrix may open up a newly/novel and feasible area for the advanced engineering, heavy-industrial technology and large-scale applications of type-II superconducting materials. (C) 2021 Elsevier B.V. All rights reserved.Öğe Re-examination of β-decay in Hg, Pb and PoIsotopes(Iop Publishing Ltd, 2023) Nabi, Jameel-Un; Bayram, Tuncay; Riaz, Muhammad; Ullah, Asim; Hayder, Anes; Şentürk, Şevki; Böyükata, MahmutThis study re-examines the effect of nuclear deformation on the calculated Gamow-Teller (GT) strength distributions of neutron-deficient (Hg178-192, Pb185-194 and Po196-206) nuclei. The nuclear ground state properties and shape parameters were calculated using the Relativistic Mean Field model. Three different density-dependent interactions ((DC)-C-3, DD-ME2 and DD-PC1) were used in the calculation. Estimated shape parameters were later used within the framework of deformed proton-neutron quasi-random phase approximations model, with a separable interaction, to calculate the GT strength distributions, half-lives and branching ratios for these neutron-deficient isotopes. It was concluded that half-lives and GT strength distributions vary considerably with change in shape parameter.Öğe Re-examination of nuclear structure properties and shape co-existence of nuclei around A ∼ 70(Elsevier, 2024) Nabi, Jameel-Un; Bayram, Tuncay; Böyükata, Mahmut; Ullah, Asim; Hayder, Anes; Naqvi, Syeda ZainabWe re-examine the nuclear structure properties of waiting point nuclei around A similar to 70 using the interacting boson model-1 (IBM-1) and the relativistic mean field (RMF) model. Effective density-dependent meson-exchange functional (DD-ME2) and density-dependent point-coupling functional (DD-PC1) were used for the RMF calculations. We calculated the energy levels, the geometric shapes, binding and separation energies of nucleons and quadrupole deformation parameters (beta 2). The shape co-existence phenomena in A similar to 70 nuclei (Se-68, Se-70, Br-70, Kr-70, Kr-72, Kr-74, Rb-74 and Sr-74) was later investigated. Spherical and deformed shapes of the selected waiting point nuclei were computed using the IBM-1 and RMF models, respectively. The proton-neutron quasiparticle random phase approximation (pn-QRPA) model was used to calculate beta-decay properties (Gamow-Teller strength distributions, beta-decay half-lives and branching ratios) of selected nuclei as a function of beta 2. The results revealed a significant variation in calculated half-lives and Gamow-Teller strength distributions as the shape parameter was changed. The beta 2 computed via DD-ME2 functional resulted in half-lives in best agreement with the measured data.Öğe Perpendicular Magnetic Anisotropy Revealed by c/a Ratio of Mn2NiB Heusler Alloy(Springer, 2021) Yağcı, Nermin Kahvecic/a ratio effects on the magnetic properties of the Mn2NiB Heusler alloy are investigated by using effective field theory developed by Kaneyoshi. It is found that the Curie temperature and coercive fields of the Mn2NiB are obtained as Tc-IT > Tc(C) > Tc-NT = 0.92 and Hc(IT) > Hc(C) > Hc(NT) = 0.00 for c/a < 1 (inverse tetragonal), c/a = 1 (cubic), and c/a > 1 (normal tetragonal), respectively. These magnetic differences show that the c/a ratio causes a perpendicular magnetic anisotropy (PMA). Therefore, we suggest that PMA strongly depends on the c/a ratio, atomic distance, and exchange interactions between two atoms (Mn-Ni and Mn-B) on the ca surfaces of the Mn2NiB.Öğe Nuclear structure properties and weak interaction rates of even-even Fe isotopes(Elsevier, 2024) Nabi, Jameel-Un; Böyükata, Mahmut; Ullah, Asim; Riaz, MuhammadNuclear structure properties and weak interaction rates of neutron -rich even-even iron (Fe) isotopes (A = 50 - 70) are investigated using the Interacting Boson Model -1 (IBM -1) and the proton-neutron Quasiparticle Random Phase Approximation (pn-QRPA) model. The IBM -1 is used for the calculation of energy levels and the B(E2) values of neutron -rich Fe isotopes. Later their geometry was predicted within the potential energy formalism of the IBM -1 model. Weak interaction rates on neutron -rich nuclei are needed for the modeling and simulation of presupernova evolution of massive stars. In the current study, we investigate the possible effect of nuclear deformation on stellar rates of even-even Fe isotopes. The pn-QRPA model is applied to calculate the weak interaction rates of selected Fe isotopes using three different values of deformation parameter. It is noted that, in general, bigger deformation values led to smaller total strength and larger centroid values of the resulting Gamow-Teller distributions. This later translated to smaller computed weak interaction rates. The current finding warrants further investigation before it may be generalized. The reported stellar rates are up to 4 orders of magnitude smaller than previous calculations and may bear astrophysical significance.Öğe Nanostructures of Molybdenum, Chromium, and Tungsten Constructed by a Basic Structural Unit(Amer Chemical Soc, 2024) Demirci, Salih; Jahangirov, Seymur; Çıracı, SalimWe predicted a stable, zigzag chain structure of Molybdenum Mo, which, being a basic structural unit, can construct stable 0D or quantum dot (segments of atomic chains and rings), 1D (various infinite chains), quasi-1D (nanoribbons and nanotubes), and 2D (bilayers) structures entailing critical magnetic, elastic, and electronic properties. This zigzag chain, constituted by strong Mo-Mo covalent bonds, is a nonmagnetic semiconductor but undergoes an insulator-metal transition under compression acquiring a ferromagnetic state. Although Mo cannot form stable, suspended, 2D monolayers of a single atomic plane, parallel zigzag chains bound by metallic interchain interaction can construct stable bilayers of different symmetry, and also their stacks forming slabs. These bilayers, being elemental Dirac materials and displaying directional properties, clarify the ambiguous situation in recent studies synthesizing and/or predicting different 2D molybdenene structures. Notably, other Group VIB elements, chromium, and tungsten, also construct similar atomic chains and 2D bilayers with diverse physical properties. Intriguingly, an atomic chain structure serves as a building block for many low-dimensional materials with diverse physical properties, making it unique in nanoscience.Öğe Can Stable MoS2 Monolayers and Multilayers Be Constituted in the Biphenylene Network?(Amer Chemical Soc, 2023) Gorkan, Taylan; Demirci, Salih; V. Barth, Johannes; Aktürk, Ethem; Çıracı, SalimBased on the first-principles calculations, we predict that the well-known 2H-MoS2 monolayer of the trigonal prismatic phase appearing in a hexagonal network can also constitute another stable phase in the biphenylene network (B-MoS2). It consists of the connected octagon, hexagon and square rings and hence maintains the same numbers of neighbors of the constituent atoms, but its bonds between transition metal and chalcogen atoms are deformed to construct a direct but narrow band gap semiconductor with directional electronic conduction and optical properties with strong absorption in the near-infrared region. It has softer mechanical properties and site specific chemical activities of the same kind of constituent atoms. In the same way, vacancies of different chalcogen atoms in the cell attain different defect states in the band gap. This phase can remain stable above the room temperature and has a cohesive energy comparable to all the other 2D phases of the same compound. In fact, transitions from the 2H-phase to the B-phase can be possible. The B-phase can form multilayers and also a metallic 3D layered, van der Waals crystal with weak interlayer coupling. The narrow band gap of the monolayer is reduced in the bilayer but diminishes in multilayers and 3D layered crystals to change the semiconductor to a metal. Even more interesting is that B-MoS2 is versatile for the modulation of the band gap, even for the metal-insulator transition under applied strains.Öğe Sınıf Öğretmeni Adaylarının Fen ve Teknoloji Laboratuvarında Kullanılan Deney Türlerinin Motivasyon ve Kavramalarına Etkisiyle İlgili Görüşleri(2019) Aydın, Nilgün; Aydın, AbdullahFen deneyleri, yapılış şekillerine, amaçlarına ve yapılış zamanına göre üç başlık altında toplanabilir. Bu araştırmanın amacı, sınıf öğretmeni adaylarının fen ve teknoloji laboratuvarı derslerinde kullanılan deney türlerinin motivasyonlarını ve kavramalarını nasıl etkilediğiyle ilgili görüşlerinin belirlenmesidir. Bu amaçla araştırmada olgubilim (fenomenoloji) deseni kullanılmıştır. Çalışma grubunu bir devlet üniversitesinin, Eğitim Fakültesi, Sınıf Öğretmenliği Anabilim Dalı’nda 2017-2018 eğitim-öğretim yılı bahar döneminde 2.sınıfta öğrenim gören 52 öğretmen adayı oluşturmaktadır. Verilerin elde edilmesinde 4 tane açık uçlu sorudan oluşan yarı yapılandırılmış görüşme formu kullanılmıştır. Bulgulara göre çalışma grubundaki öğretmen adaylarının %48,08’i, yapılış şekline göre hem gösteri hem de grup deneylerinin, %17,3’ü tamamen grup deneylerinin, %28,8’i tamamen gösteri deneylerinin, %5,7’si de bireysel deney yapılması yönünde görüş bildirmişlerdir. Öğretmen adaylarının %59,6’sının yapılış amacına göre kapalı uçlu deneyleri, %19,23’ünün açık uçlu deneyleri, %17,3’ünün hem kapalı uçlu hem de açık uçlu deney türünü %3,8’inin de hipotez test etme deneyini tercih ettikleri görülmüştür. Araştırmanın sonuçlarına göre, öğretmen adaylarının farklı deney yapma türlerini tercih ettikleri ve bu tercihleri doğrultusunda deneyler yapıldığında motivasyon ve kavramalarının daha olumlu etkileneceği yönünde görüş bildirdikleri görülmüştür.Öğe Physical Properties of Martensitic Phase Transformations in Fe - 18.79%Mn-4.53%Ni Alloys(2016) Türk, Dilek; Yağcı, Nermin KahveciBu çalışmada, Fe-%18,79Mn-%4,53Ni alaşımında termal etki ile oluşturulan martensitik faz dönüşümlerinin kristalografik ve manyetik özellikleri araştırıldı. Taramalı Elektron Mikroskobu (SEM) ile termal etkili martensitelerin mikroyapıları incelendi. Mikroyapı incelemelerinde, termal etkili martensite yapı miktarının uygulanan sıcaklık derecelerinin artması ile arttığı gözlendi. Austenite faz içerisinde oluşan termal etkili martensite fazın hacim yüzdeleri Mössbauer Spektrometresi tekniği yoluyla belirlendi. X-ışını tekniği ile örgü parametrelerinde meydana gelen değişimler tespit edildiÖğe Hydroxyapatite-based nanoparticles as a coating material for the dentine surface: An antibacterial and toxicological effect(ELSEVIER SCI LTD, 2020) Erdem, Umit; Dogan, Mustafa; Metin, Aysegul U.; Baglar, Serdar; Turkoz, Mustafa B.; Turk, Mustafa; Nezir, SaffetIn this study, nano sized hydroxyapatite (nHAp) and Ag(I) doped hydroxyapatite (Ag-nHAp) particles were synthesized by the precipitation method and used as a coating material for remineralization on caries-affected dentine samples. Characterization studies of both the synthesized hydroxyapatite-based particles and the coated dentine samples were performed using instrumental techniques such as SEM and FFIR, and then toxicity and antibacterial properties were also evaluated. It was observed that dentine samples were effectively coated by both nHAp and Ag center dot nHAp particles which have no toxic effects. Furthermore, the costing of nano-hydroxyapatite on dentine samples positively contributed to the viability of L929 fibroblast cells and also provided an antibacterial effect against to bacteria such as S. mutants, C. albicans and E. coli bacteria that are most frequently caused caries in the teeth. While all type of bacteria was eliminated by the nHAp coated dentine samples at 24th, Ag-nHAp coated dentine samples removed to all bacteria type at 1st.Öğe Temperature, strain and charge mediated multiple and dynamical phase changes of selenium and tellurium(ROYAL SOC CHEMISTRY, 2020) Demirci, Salih; Gürel, Hikmet Hakan; Jahangirov, Seymur; Çıracı, SalimSemiconducting selenium and tellurium in their 3D bulk trigonal structures consist of parallel and weakly interacting helical chains of atoms and display a number of peculiarities. We predict that thermal excitations, 2D compressive strain and excess charge of positive and negative polarity mediate metal-insulator transitions by transforming these semiconductors into different metallic crystal structures. When heated to high temperature, or compressed, or charged positively, they change into a simple cubic structure with metallic bands, which is very rare among elemental crystals. When charged negatively, they transform first into body-centered tetragonal and subsequently into the body-centered orthorhombic structures with increasing negative charging. These two new structures stabilized by excess electrons also have overlapping metallic bands and quasi 2D and 1D substructures of lower dimensionality. Since the external charging of crystals can be achieved through their surfaces, the effects of charging on 2D structures of selenium and tellurium are also investigated. Similar structural transformations have been mediated also in 2D nanosheets and free-standing monolayers of these elements. These phase changes assisted by phonons are dynamical, reversible and tunable; the resulting metal-insulator transitions can occur within very short time intervals and may offer important device applications.Öğe Electronic, Elastic, Vibrational and Thermodynamic Properties of HfIrX (X = As, Sb and Bi) Compounds: Insights from DFT-Based Computer Simulation(SPRINGER, 2020) Arikan, Nihat; Dikici Yildiz, Gokcen; Yildiz, Yasin Gokturk; Iyigor, AhmetAb-initio calculations were performed to reveal and thoroughly understand the structural, electronic, elastic, thermodynamic and vibrational properties of HfIrX (X = As, Sb and Bi) compounds in the C1(b) phase. Basic physical characteristics, such as bulk modulus, pressure derivative of bulk modulus, anisotropy factor, shear modulus, Poisson's ratio, Cauchy pressure, elastic constants and Young's modulus were obtained and some of them were compared with those in the literature. Electronic band structure, the density of states and phonon dispersion curves were obtained and compared with current theoretical calculations. It was concluded according to current band structure calculations that the HfIrAs and HfIrBi compounds showed semimetal characteristics, while the HfIrSb compound behaves as a semiconductor. It was determined based on phonon calculations that all three compounds were dynamically stable. Various thermodynamic properties, such as heat capacity, thermal expansion coefficient values and Gruneisen parameter were calculated under constant volume and constant pressure by using Gibbs2 code within the Quasi-harmonic approach, and these results are discussed.Öğe Intersection Magnetization and Temperature Revealed by FCC-FCT Phase Transformation in the FePd Binary Alloy System(SPRINGER, 2020) Yildiz, Gokcen DikiciThis study investigated the fcc-fct phase transformation effect on the magnetic properties of the FePd alloy system by means of the effective field theory (EFT) developed by Kaneyoshi (1993). We determined the thermal magnetization loop and magnetic hysteresis loop of fcc-FePd and fct-FePd for both the ferromagnetic (FM) and antiferromagnetic (AFM) case. We found that the FM fcc-FePd and fct-FePd have a single thermal magnetization area, whereas AFM fcc-FePd and fct-FePd have binary thermal magnetization area. In the AFM case, the magnetization curves for fcc-FePd and fct-FePd had an intersection temperature point (Ti = 1.33 at H = 0). At Ti, the magnetization value of the fcc-FePd and fct-FePd was almost the same (Mi = 0.59) and we call this magnetization the intersection magnetization. However, the magnetic hysteresis loop area of the fcc-FePd was higher than that of the fct-FePd for both the FM and AFM case. Fcc-fct phase transformation has a strong effect on the FM and AFM properties of the FePd binary alloy system.
