Mössbauer spectroscopic study of the reductive decomposition of iron(III) complexes

Iron injections containing high spin iron(III) complexes may undergo a reductive decomposition during preparation or storage. This process was investigated by the Mössbauer spectroscopy of ice samples prepared by quick-freezing of the injection. The comparison of three model compounds and the correlation between the osmotic pressure of the solutions and their iron(II) concentration formed in the decomposition process and determined by Mössbauer measurements revealed the reason and mechanism of the decomposition.     

Effect of the amine type on thermal stability of modified mesoporous silica used for CO2 adsorption

In this study, the preparation by grafting of amino-functionalized SBA-15 molecular sieves was carried out. Amino-functionalized molecular sieves were synthesized using a silane coupling agent and different types of amination reagents which react with modified SBA-15. These composites were characterized by FT-IR spectroscopy, X-ray diffraction at low angles, nitrogen physisorption at 77 K, and evaluated by the adsorption of CO₂ and its temperature-programmed desorption—TPD. Thermal stability was investigated by TGA and DTA methods. In the view of a possible use of these amino-functionalized molecular sieves as sorbents for CO₂ removal, their adsorption–desorption properties towards CO₂ were also investigated by the TPD method. The mass loss of amino-functionalized molecular sieves above 215 °C was due to the oxidation and decomposition of amino propyl functional groups. This means that these composites could be used for adsorption of CO₂ at temperatures below 215 °C. The adsorption of CO₂ and its temperature programmed desorption using thermogravimetry were studied for amino-functionalized molecular sieves at 60 °C. The evolved gases during the adsorption–desorption of CO₂ on amino-functionalized molecular sieves were identified by online mass spectrometry coupled with thermogravimetry. CO₂ adsorption isotherms of functionalized samples at 60 °C showed that both the adsorption capacity (mg CO₂/g adsorbent) and the efficiency of amino groups (mol CO₂/mol NH₂) depend on the type of amination reagents and the amount of organic compound used.

     

Study of chemical bonding in H2 and HF molecules: Wave function and density functional theory (DFT) parameters approach

Balint Kurti's Fourier grid Hamiltonian method is employed to obtain the molecular wave function and equilibrium bond length for H₂ and HF molecules. The density functional theory parameter, namely, the chemical hardness (η) value, was determined for some diatomic hydride molecules using this wave function and the results are found to be in good agreement with the values obtained from the ab initio HF–SCF method. A new formula for chemical hardness (η=1/2Dr, where D is the proportionality constant and r is the internuclear distance) is introduced in binding energy and change of hardness equations to determine the chemical hardness and chemical potential values for different bond lengths. The binding energy and change of hardness values are calculated for H₂, H, H, HF, HF⁺, and HF⁻ molecules and the bond stability is discussed. Finally, the concept of an atom in a molecule is examined in the context of DFT parameters and comparison is made between an atom in a molecule and the isolated atom. © 2000 John Wiley & Sons, Inc. Int J Quant Chem 76: 662–669, 2000     

Light trapping effect in silicon wafers with anodically etched surfaces

Received: 10 May 1996/Accepted: 19 November 1996     

A difference method for solving parabolic equations of order 2n

In this paper, a finite difference method is used to approximate for the solution of the parabolic partial differential equation of order 2n and error of the method is determined. The resulting system is solved by efficient implicit iterations. In some numerical examples, MAPLE modules are designed for the purpose of testing and using the method.     

A simple spectrophotometric method for the determination of zirconium in U–Zr alloy samples in presence of fluoride ions

Journal of Radioanalytical and Nuclear Chemistry - A spectrophotometric method, circumventing interference from F− ions, during estimation of Zr in U-Zr alloy fuel, has been developed....     

Electrochemical Evaluation of Titanium (IV) Oxide/Polyacrylonitrile Electrospun Discharged Battery Coals as Supercapacitor Electrodes

The TiO₂ nanoparticles are electrospun with polyacrylonitrile (PAN) polymer solution onto the discharged battery coal (DBC) electrode and the results are evaluated as a supercapacitor. The morphology and chemical composition of the synthesized TiO₂ nanoparticles and PAN+TiO₂ nanocomposite fibers were characterized by Scanning electron microscopy, thermogravimetry and FTIR analysis. Supercapacitor measurements and electrochemical characterizations of the electrodes examined by cyclic voltammetry and electrochemical impedance spectroscopy. Electrochemical measurements showed that the best current value was obtained from PAN and TiO₂ coated DBC. The performances of both PAN and PAN+TiO₂ coated DBC electrodes were investigated as supercapacitors. PAN+TiO₂/DBC showed the best specific capacitance value of 156.00 F g⁻¹ and PAN/DBC showed 74.93 F g⁻¹. In addition, PAN+TiO₂/DBC exhibited reliable stability performance over 2000.00 cycles.     

Synthesis of 3-(2-benzothiazolylthio)propanenitrile and related products

The reaction of 2-mercaptobenzothiazole, 2-mercaptobenzoxazole or 5-chloro-2-mercaptobenzothiazole with either acrylonitrile or acrylamide under basic conditions afforded the N-cyanoethylated products 1, 2 and 3 or the N-amidoethylated products 4, 5 and 6 , respectively. The reaction of the sodium salts of the same thiazolethiols with 3-chloropropionitrile furnished a mixture containing the N-cyanoethylated products 1, 2 and 3 and the unknown S-cyanoethylated products 7, 8 and 9 , respectively. Whereas, substituting 3-chloropropionamide for 3- chloropropionitrile in the same reaction gave only the S-substituted products 10, 11 , and 12 , respectively. The treatment of 10, 11 or 12 with phosphorus oxychloride or thionyl chloride in DMF afforded 7, 8 and 9 in excellent yields. Possible mechanisms and supporting nmr data are discussed.     

Mössbauer study of mixed-ligand complexes of europium(III)

A series of europium(III) mixed complexes was prepared containing 1,10-phenanthroline or 2,2-bipyridine as neutral ligand and simple inorganic anions or benzoate and its derivatives as ionic ligands. The Mössbauer spectra of the products indicated that both types of ligands were directly coordinated to the central europium(III) atom. The Mössbauer isomer shift values reflected both electron shifting and steric effects of the substituents on the ligand. The quadrupole splitting values pointed to the similar symmetry of the electron shell of the europium in almost all complexes with analogous composition. The IR spectra provided evidence of the binding mode of the carboxylate groups in the complexes containing benzoate or its derivatives. The x-ray photoelectron spectra of the compounds demonstrated the effects of electrophilic and nucleophilic substituents on the electron binding energies in the europium, oxygen, and nitrogen orbitals.