Ahmet Yasin Ay - Academia.edu (original) (raw)

Papers by Ahmet Yasin Ay

BMB Reports, 2003

The relative activities of neutral, cationic, and anionic chromium ascorbate complexes toward iso... more The relative activities of neutral, cationic, and anionic chromium ascorbate complexes toward isolated human mitochondrial and genomic DNA were investigated at physiologically relevant conditions by agarose gel electrophoresis. A direct relationship between the charge of the Cr(III) species and their DNA-damaging properties was found. The cationic species were found to be fully capable of DNA-cleavage, even in short incubation periods. Incubations were also performed in the presence of amino acids. No apparent effect was observed under the applied experimental conditions to facilitate or prevent damage through the ternary amino acid-Cr-DNA adduct formation or binary chromium-amino acid complex formation.

$Research paper thumbnail of Boron isotopic fractionation in aqueous boric acid solutions over synthetic minerals: Effect of layer and surface charge on fractionation factor$

Applied Clay Science, 2015

ABSTRACT Boron isotopic fractionation in boric acid solutions during adsorption on synthetic mang... more ABSTRACT Boron isotopic fractionation in boric acid solutions during adsorption on synthetic manganese oxides (birnessite “B” and cryptomelane “C”) and Mg–Al-layered double hydroxide “LDH” was investigated. The materials were characterized by elemental analyses, powder X-ray diffraction, FTIR spectra, BET surface area and zeta potential measurements. Batch experiments were conducted without changing the solution pH to correlate the boron sorption properties of the adsorbents with isotopic fractionation in the associated boric acid solutions. The results showed that boron isotopic composition of the contact solution is heavily dependent on the selective adsorption of B(OH)3 or B(OH)4− species due to the charge properties of the minerals. With B and C, possessing negatively charged surfaces, 10B(OH)4− was preferentially fractionated in the solution due to the transfer of the Lewis acidic 11B(OH)3 species while with LDH selective adsoption of 10B(OH)4− by positive layers was favorable resulting in the enrichment of the heavier isotope in the solution.

Zeitschrift für anorganische und allgemeine Chemie, 2009

Hydrotalcite-like Mg-Al-NO 3-layered double hydroxide (LDH) was successfully prepared in a mortar... more Hydrotalcite-like Mg-Al-NO 3-layered double hydroxide (LDH) was successfully prepared in a mortar by manually grinding the hydrated magnesium and aluminum nitrate salts with sodium hydroxide. Various techniques, including XRD, MAS NMR, FTIR, SEM; thermogravimetric and differential thermal analyses (TGA,DTA), surface area and zeta potential measurements were used to establish a correlation between the LDH samples prepared in the mortar and by co-precipitation. The LDH prepared in the

Synthesis and Reactivity in Inorganic and Metal-Organic Chemistry, 2002

Two new Cr(III)-ascorbate complexes, K[Cr(C6H7O6)2(OH)2-(H2O2)2]·3H2O (1) and K2[Cr(C6H7O6)3(OH)2... more Two new Cr(III)-ascorbate complexes, K[Cr(C6H7O6)2(OH)2-(H2O2)2]·3H2O (1) and K2[Cr(C6H7O6)3(OH)2(H2O)]·2H2O (2), have been prepared by reducing chromate with L-ascorbic acid in aqueous THF. The complexes have been characterized by various analytical and spectroscopic methods (UV/Vis, FTIR, C NMR and EI MS) and by thermal and magnetic measurements. Experimental results indicated a distorted octahedral environment around the Cr(III) centers and the coordination mode

Nanoscale Research Letters, 2011

A new nanocomposite architecture is reported which combines prolate spheroidal hematite nanoparti... more A new nanocomposite architecture is reported which combines prolate spheroidal hematite nanoparticles with drug-carrying layered double hydroxide [LDH] disks in a single structure. Spindle-shaped hematite nanoparticles with average length of 225 nm and width of 75 nm were obtained by thermal decomposition of hydrothermally synthesized hematite. The particles were first coated with Mg-Al-NO3-LDH shell and then subjected to anion exchange with salicylate ions. The resulting bio-nanohybrid displayed a close structural resemblance to that of the Ring Nebula. Scanning electron microscope and transmission electron microscopy images showed that the LDH disks are stacked around the equatorial part of the ellipsoid extending along the main axis. This geometry possesses great structural tunability as the composition of the LDH and the nature of the interlayer region can be tailored and lead to novel applications in areas ranging from functional materials to medicine by encapsulating various g...

Microporous and Mesoporous Materials, 2007

... Borate exchange with HT materials has been studied by several investigators. Parker et al. [1... more ... Borate exchange with HT materials has been studied by several investigators. Parker et al. [16] and Shi et al. [19] studied borate exchange with CO 3 -HT compounds. del Arco et al. ... Catal. Today, 11 (1991), p. 173. [16] LM Parker, NB Milestone and RH Newman. Ind. Eng. ...

Materials Science and Engineering: C, 2011

Mg–Al-layered double hydroxide intercalated with a model drug, salicylate, was deposited on labor... more Mg–Al-layered double hydroxide intercalated with a model drug, salicylate, was deposited on laboratory-made magnesium ferrite and commercial magnetite nanoparticles. The obtained core–shell nanocomposites have been characterized by a variety of methods. The combined information from X-ray diffraction patterns, electron diffraction patterns, FTIR spectra, X-ray photoelectron spectra, electron microscopy images, thermogravimetric analysis and microchemical analysis has indicated a similar nature and

Journal of Thermal Analysis and Calorimetry, 2010

... layered double hydroxides A study on thermal decomposition kinetics and mechanism Ahmet Nedim... more ... layered double hydroxides A study on thermal decomposition kinetics and mechanism Ahmet Nedim Ay Received: 6 September 2010 / Accepted: 30 September 2010 / Published online: 17 October 2010 Ó Akadémiai Kiadó, Budapest, Hungary 2010 ...

Journal of the Iranian Chemical Society, 2012

The title compound, diaqua(bissalicylato-jO) (bisnicotinamide-jN)zinc(II)][bis(triaqua (monosalic... more The title compound, diaqua(bissalicylato-jO) (bisnicotinamide-jN)zinc(II)][bis(triaqua (monosalicylato-jO) (mononicotinamide-jN)zinc(II)salicylate, includes three Zn(II) ions, four nicotinamide ligands, six salicylate ligands and eight coordinated aqua ligands in the asymmetric unit in complex structure. The geometry around one of the Zn(II) ions is a slightly distorted octahedron, of which the equatorial plane is formed by two carboxylate oxygens and two aqua oxygens, while the axial positions are occupied by two pyridyl nitrogen atoms. The other Zn(II) ions adopt fivefold coordinations with one carboxylate oxygen atom from salicylate ligand, one N atom from nicotinamide ligand and three oxygen atoms from aqua ligands. In addition, there are two salicylate anions in the unit cell that are not coordinated. They provide charge balance as counter-ions in the complex framework. Keywords Zn(II) complexes Á Mixed-ligand complexes Á Salicylic acid complexes Á Nicotinamide complexes Á Penta-coordinated Zn(II) Á Hexa-coordinated Zn(II)

Transition Metal Chemistry, 2002

Two polynuclear complexes, a dimer and a tetramer, involving sulfate and hydroxo bridges and liga... more Two polynuclear complexes, a dimer and a tetramer, involving sulfate and hydroxo bridges and ligating ascorbate were isolated from aqueous solutions. Structural formulae are proposed on the basis of microanalytical and thermal analysis results, i.r., 13C-n.m.r., mass spectral data and magnetic measurements.

Journal of Applied Polymer Science, 2005

ABSTRACT The effects of aging time of Cr(III) solutions on the structural, thermal, magnetic, and... more ABSTRACT The effects of aging time of Cr(III) solutions on the structural, thermal, magnetic, and morphological properties of chromium polyacrylate complexes were studied. Chromium retention was found to increase with longer aging periods. IR spectra revealed the formation of polychelate structures with noticeable changes on aging. The interaction of multivalent, polynuclear Cr(III) species with the polymer backbone resulted in a decrease in thermal stability for the complexes prepared from olated chromium solutions. © 2005 Wiley Periodicals, Inc. J Appl Polym Sci 98: 490–493, 2005

Journal of Applied Polymer Science, 2007

Thermogravimetric studies of poly(acrylic acid) (PAA) and its chromium-polyacrylate complexes pre... more Thermogravimetric studies of poly(acrylic acid) (PAA) and its chromium-polyacrylate complexes prepared from Cr(III) solutions aged for different times were undertaken. Six kinetic methods were used to investigate the thermal decomposition behavior of these materials. The applied methods were the Coats-Redfern, Horowitz-Metzger, MacCallum-Tanner, van Krevelen, Madhusudanan-Krishnan-Ninan, and Criado methods. The activation energy values obtained with the Coats-Redfern, Horowitz-Metzger, and MacCallum-Tanner methods were in good agreement with one another, and those obtained with the van Krevelen and Madhusudanan-Krishnan-Ninan methods were found to be 10-20 kJ/mol larger. The apparent activation energies increased for the complexes prepared from Cr(III) solutions aged for longer times. An analysis of the experimental results suggested that the actual decomposition mechanisms of PAA and the metal-polymer complexes were a D n deceleration type.

Inorganic Chemistry, 2009

This paper describes the synthesis and characterization of a composite constituted by an antiarth... more This paper describes the synthesis and characterization of a composite constituted by an antiarthritic agent (AA) intercalated into a layered double hydroxide (LDH) supported on magnesium ferrite. Core-shell nanocomposites were prepared by depositing Mg-Al-NO 3-LDH on a MgFe 2 O 4 core prepared by calcination of a nonstoichiometric Mg-Fe-CO 3-LDH. Intercalation of ibuprofen and glucuronate anions was performed by ion-exchange with nitrate ions. The structural characteristics of the obtained products were investigated by powder X-ray diffraction, element chemical analysis, Fourier transform infrared spectroscopy, and thermogravimetric analysis. Morphologies of the nanocomposite particles were examined by scanning electron microscopy and transmission electron microscopy. The products were shown to intercalate substantial amounts of AA with enhanced thermal stabilities. Room-temperature magnetic measurements by vibrating sample magnetometry revealed that the products show soft ferromagnetic properties suitable for potential utilization in magnetic arthritis therapy.

Inorganic Chemistry Communications, 2013

A novel magnetic composite catalyst has been prepared by immobilizing a palladium(0) complex, Pd ... more A novel magnetic composite catalyst has been prepared by immobilizing a palladium(0) complex, Pd 2 (dba) 3 , onto Mg-Al-layered double hydroxide shell supported on magnetite core. This new catalyst was characterized by XRD, TEM, EDX, FTIR, XPS, thermogravimetry and microanalytical techniques and magnetometric measurements. The performance of the catalyst was tested in the Heck and Suzuki reactions and confirmed to be efficient in the cross-coupling of aryl iodides under mild conditions.

Chemical Papers, 2012

Layered double hydroxides (LDH’s), also known as anionic clays, are lamellar inorganic solids. Th... more Layered double hydroxides (LDH’s), also known as anionic clays, are lamellar inorganic solids. The structure of most of them corresponds to that of mineral hydrotalcite, consisting of brucite-like hydroxide sheets, where partial substitution of trivalent or divalent cations results in a positive sheet charge compensated by reversibly exchangeable anions within interlayer galleries. These layered materials have good intercalation properties capturing inorganic and organic ions and they are promising materials for a large number of practical applications, both for direct preparation and for after thermal treatment.Over the past decade, significant interest has been devoted to the synthesis of LDHs with new compositions allowing improved applications in many areas. This contribution reviews the recent advances in water treatment, nuclear waste treatment/storage, catalytic, industrial, and advanced applications and biomedical applications of LDH-based nanomaterials.

Applied Clay Science, 2011

... LDHs, particularly the nitrate-intercalated LDHs, have good anion exchange capacities toward ... more ... LDHs, particularly the nitrate-intercalated LDHs, have good anion exchange capacities toward inorganic ( [Meyn et al., 1990] and [Parker et al., 1995] ) and organic anions ( [Khan and O'Hare, 2002] , [Newman and Jones, 1998] and [Williams et al., 2006] ) which enable them to ...

Acta Crystallographica Section E Structure Reports Online, 2010

Acta Cryst. (2010). E66, m612-m613 Ay et al. [Co(C 5 H 3 N 2 O 4) 2 (H 2 O) 4 ]Á2H 2 O m613