Browsing by Author "Çelik, Ö."
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Item Open Access Aromatik asit içeren bazı kristallerin molekül yapılarının X-ışınları kırınımı yöntemiyle incelenmesi ve kuantum mekaniksel hesaplamaları(Türkiye Kimya Derneği, 2015) Aslantaş, M.; Karayel, Arzu; Çelik, Ö.; Arslan, A.Aromatic-structured acids and their complexes are having with biological importance, in particular molecules which are used in the food industry due to enzymatic activity and antimicrobial properties. In this study, crystal structure analyses were performed by X-ray diffraction method, and biological analysis of synthesized aromatic-structured complex molecules determined. In order to support and compare of the experimental results for these complexes, the quantum mechanical Hartree-Fock (HF) and Density Functional Theory (DFT) methods were investigated by theoretical calculations. Many information at the atomic level for the complex molecules such as, conformations in the unit cell, energies, bond lengths and angles, molecular packing, intra- and inter-molecular hydrogen bonding interactions were presented.Item Unknown Lyotropic liquid-crystalline phase of oligo(ethylene oxide) surfactant/transition metal salt and the synthesis of mesostructured cadmium sulfide(American Chemical Society, 2003) Dag, Ö.; Alayoǧlu, S.; Tura, C.; Çelik, Ö.Lyotropic liquid-crystalline (LLC), transition metal salt: oligo(ethylene oxide) nonionic surfactant (CnH2n+1(CH2CH2O)mOH, denoted as CnEOm), systems have been studied by means of diffraction, microscopy, and spectroscopy to elucidate the structural, thermal, and templating properties. In the system, the lyotropic salts of transition metal aqua complexes, such as chlorides and sulfates, are insoluble and do not form a LC phase in CnEOm-type nonionic surfactants. However, the transition metal aqua complexes of nitrates and perchlorates are soluble and form 2D and 3D hexagonal and cubic mesophases. These phases are stable in a very broad range of salt:surfactant mole ratios (1.0 and 3.6). The nitrate salts form a hexagonal mesophase. However, in high nitrate salt concentrations (above 3.2 salt:surfactant mole ratio), the salt crystals are either insoluble or the salt:surfactant mixtures are in a cubic mesophase. The structure and thermal properties of the new system are determined by the solubility of the transition metal salts, the concentration of the salt, and the surfactant type. The LC [Cd(H2O)4](NO3)2: C12EO10 mesophase has been reacted with H2S gas to produce solid mesostructured CdS (meso-CdS). The meso-CdS particles are spherical in morphology and are made up of hierarchical organization of 2-4-nm CdS particles. The salt:surfactant LLC systems and the solid meso-CdS have been investigated using polarized optical microscopy, X-ray diffraction, Fourier transform infrared, Fourier transform Raman, and UV-vis absorption spectroscopy, scanning electron microscopy, and transmission electron microscopy.Item Open Access A new lyotropic liquid crystalline system: oligo(ethylene oxide) surfactants with [M(H2O)n]Xm transition metal complexes(Wiley, 2001) Çelik, Ö.; Dag, Ö.Coordinated water molecules induce the aggregation and self-assembly of the lyotropic liquid crystalline phase formed from non-ionic surfactants CnH2n+1(CH2CH2O)mOH and transition metal aqua complexes ([Ni(H2O)6](NO3)2, [Co(H2O)6](NO3)2, [Cd(H2O)4](NO3)2, and [Co(H2O)6]Cl2) into hexagonal (see schematic representation) and/or cubic structures. While the NiII and CoII complexes undergo recrystallization and phase separation at high complex concentrations, the ZnII and CdII complexes form cubic phases above metal/surfactant molar ratios of 3.2/1 at room temperature.Item Open Access Solventless acid-free synthesis of mesostructured titania: nanovessels for metal complexes and metal nanoclusters(Wiley - V C H Verlag GmbH & Co. KGaA, 2003) Dag, Ö.; Soten, I.; Çelik, Ö.; Polarz, S.; Coombs, N.; Ozin, G. A.A new and highly reproducible method to obtain mesostructured titania materials is introduced in this contribution. The meso-structured titania is obtained by employing self-assembled structures of non-ionic alkyl-poly(ethylene oxide) surfactants as templates. The materials are produced without additional solvents such as alcohols, or even water. Only the titanium(iv) ethoxide and the surfactant (C12EO10) are needed. Water, in the form of that attached to the surfactant and from the atmosphere, induces growth of titania nanoclusters in the synthesis sol. It is indicated that these nanoclusters interact with the surfactant EO-head groups to form a new titanotropic amphiphile. The new amphiphiles self-assemble into titanium nanocluster-surfactant hybrid lyotropic phases, which are transformed to the final mesostructured materials by further condensation of the titania network. The titania materials can be obtained also with noble-metal particles immobilized in the mesostructured framework. It is seen that when different metal salts are used as the metal precursors, different interactions with the titania walls are found. The materials are characterized by X-ray diffraction (XRD), polarization optical microscopy (POM), transmission electron microscopy (TEM), UV-vis spectroscopy, and micro-Raman analysis.Item Open Access Spectroscopic investigation of nitrate-metal and metal-surfactant interactions in the solid AgNO3/C12EO10 and liquid-crystalline [M(H2O)n](NO3)2/C12EO10 systems(American Chemical Society, 2003) Dag, Ö.; Samarskaya, O.; Tura, C.; Günay, A.; Çelik, Ö.Interactions of the nitrate ions in various metal nitrate salts with CnH2n-1(CH2CH2O)mOH (CnEOm)-type nonionic surfactants have been investigated both in the solid and in the liquid-crystalline (LC) systems. In the ternary system, the mixture of salt/water/CnEOm has a mesophase up to a certain concentration of salt, and the nitrate ions in this phase are usually in a free-ion form. However, upon the evaporation of the water phase, the nitrate ion interacts with the metal center and coordinates as either a bidentate or unidentate ligand. It is this interaction that makes the AgNO3 ternary system undergo a phase separation by releasing solid Ag(CnEOm)xNO3 complex crystals. In contrast, the salt/surfactant systems maintain their stable LC phases for months. Note also that the salt/surfactant systems consist of transition-metal aqua complexes in which the coordinated water molecules play a significant role in the self-assembly and organization of the nonionic surfactant molecules into an LC mesophase. Throughout this work, Fourier transform infrared spectroscopy has been extensively used to investigate the interactions of the nitrate ions with a metal center and the metal ions with the surfactant molecules. Polarized optical microscopy and X-ray diffraction techniques have been applied to investigate the nature of the crystalline and LC phases.