Polyoxotungstate Archetype {P4W27} and its 3d Derivatives

The propensity of the new, phenylphosphonate-stabilized polyoxotungstate [(C₆H₅P^VO)₂P₄W₂₄O₉₂]¹⁶⁻ to act as a precursor for new 3d metal-functionalized polyanions has been investigated. Reactions with Mn^II and Cu^II induce the formation of the previously unknown polyoxotungstate archetype {P₄W₂₇}, isolated as salts of the polyanions [Na⊂{Mn^II(H₂O)}{WO(H₂O)}P₄W₂₆O₉₈]¹³⁻ ( 1 ) and [K⊂{Cu^II(H₂O)}{W(OH)(H₂O)}P₄W₂₇O₉₉]¹⁴⁻ ( 2 ), which were characterized in the solid state (single-crystal X-ray diffraction, elemental and TG analyses, IR spectroscopy, SQUID magnetometry) and in aqueous solution (UV/Vis spectroscopy, cyclic voltammetry).     

A process control method for the electric current-activated/assisted sintering system based on the container-consumed power and temperature estimation

Journal of Thermal Analysis and Calorimetry - In this paper, the current, voltage and temperature of the container of an electric current-activated/assisted sintering (ECAS) system are measured and...     

X- and gamma-ray irradiation effects on vanadium pentoxide thin films

Thickness and composition of thin films can be measured with X- and gamma-rays. In this work, thickness and composition of vanadium pentoxide thin films are investigated by energy dispersive and wavelength dispersive X-ray fluorescence systems. Also, the surface analysis of vanadium pentoxide thin films irradiated with Rhodium Kα X-rays and 59.54?keV gamma-rays emitted from 100?mCi and 5?Ci Americium-241 radioactive sources is performed by scanning electron microscope. It is observed that X- and gamma-rays are destructive for vanadium pentoxide thin films. Also, the composition of vanadium pentoxide thin films changes by irradiation with X- and gamma-rays.     

On the number of eigenvalues for parameter‐dependent diffusion problem on time scales

In this study, we consider parameter‐dependent diffusion eigenvalue problem on time scales. An upper bound on the number of eigenvalues for this problem on a finite time scale is given.     

Electro-oxidation of herbicide halosulfuron methyl on glassy carbon electrode and applications

Halosulfuron methyl, a fast-acting herbicide and is absorbed into leaf tissue within 1-2 days and translocated through the vascular system, interrupting amino acid production within the plant, can be detected using glassy carbon electrode the technique of adsorptive stripping voltammetry. The adsorptive stripping voltammetric behavior of halosulfuron methyl was investigated in pH range 1.0-10.0. Halosulfuron methyl was irreversibly oxidized at a glassy carbon electrode. Electrochemical techniques including adsorptive stripping voltammetry and cyclic voltammetry were employed to study the oxidation mechanism. The experimental parameters such as the accumulation potential, accumulation time and frequency were optimized. The linear range, detection limit and quantification for halosulfuron methyl were evaluated by adsorptive stripping voltammetry. Under the optimized conditions, the peak current is linear to halosulfuron methyl concentration in the range 4.1-50.0 μg mL⁻¹. Limit of detection and limit of quantification were 1.23 and 4.10 μg mL⁻¹, respectively. The interference of inorganic species and other some pesticides on the voltammetric response have been studied. The applicability to spiked soil and natural water was described and the recoveries for the standards added are 103.8% and 108.2%, respectively. The method is successfully applied for the determination of halosulfuron methyl in commercial formulation.     

Generation and dissociation of oxygen‐ and chloride‐bridged iron(III) and manganese(III) tetraphenylporphyrin dimer ions in the gas phase

Electrospray ionization mass spectrometry (ESI/MS) has allowed the discovery of novel dimer ions emerging from solutions of metalloporphyrin salts and their investigation by collision‐induced dissociation (CID) with N₂ molecules. ESI mass spectra have been recorded for the formation of the oxygen or chloride‐bridged dimer ions [(FeTPP)₂OH]⁺, [(MnTPP)₂OH]⁺, [(FeTPP)₂Cl]⁺ and [(MnTPP)₂Cl]⁺ derived from various solutions of FeTPPCl and MnTPPCl salts. The CID of [(FeTPP)₂OH]⁺ proceeds mainly by neutral loss of (FeTPP)OH to form [FeTPP]⁺ and, to a minor extent, to form the charge‐reversed products. The CID of [(MnTPP)₂OH]⁺ exhibits exclusively the product ion [MnTPP]⁺ by loss of neutral (MnTPP)OH. [(FeTPP)₂Cl]⁺ and [(MnTPP)₂Cl]⁺ dissociate by loss of (Fe/MnTPP)Cl to give rise to [Fe/MnTPP]⁺. [(FeTPP)₂O]⁺ and [(FeTPP)₂OH]⁺ were generated from a solution of the dimer, (FeTPP)₂O. Dissociation of [(FeTPP)₂O]⁺ yields two product ions, [FeTPP]⁺ and [(FeTPP)O]⁺, with higher onsets compared to the equivalent fragments formed from [(FeTPP)₂OH]⁺. Copyright © 2009 John Wiley & Sons, Ltd.     

Combined computational and experimental study on the inclusion complexes of β-cyclodextrin with selected food phenolic compounds

Phenolic compounds, such as caffeic acid, trans-ferulic, acid and p-coumaric acid that are commonly found in food products, are beneficial for human health. Cyclodextrins can form inclusion complexes with various organic compounds in which the physiochemical properties of the included organic molecules are changed. In this study, inclusion complexes of three phenolic compounds with β-cyclodextrin were investigated. The complexes were characterized by various analytical methods, including nuclear magnetic resonance (NMR) spectroscopy, Fourier IR (FT-IR) spectroscopy, mass spectrometry, differential scanning calorimetry, and scanning electron microscopy. Results showed that the phenolic compounds used in this study were able to form inclusion complexes in the hydrophobic cavity of β-cyclodextrin by non-covalent bonds. Their physicochemical properties were changed due to the complex formation. In addition, a computational study was performed to find factors that were responsible for binding forces between flavors and β-cyclodextrin. The quantum-mechanical calculations supported the results obtained from experimental studies. Thus, ΔH_f for the complex of p-coumaric acid and β-cyclodextrin has been found as ??11.72 kcal/mol, which was about 3 kcal/mol more stable than for inclusion complexes of other flavors. Energies of frontier orbitals (higher occupied molecular orbital (HOMO) and lower unoccupied molecular orbital (LUMO)) were analyzed, and it was found that H-L gap for the complex of p-coumaric acid and β-cyclodextrin had the largest value (8.19 eV) in comparison to other complexes, which confirmed the experimental findings of the most stabile complex.

     

Structural,Morphological and Optical Properties of Well-Ordered CdO Nanostructures Synthesized by Easy-Economical Chemical Bath Deposition Technique

In this Study, Cadmium Oxide (CdO) nanostructures were synthesized by using Chemical Bath Deposition Technique. The synthesized process was carried out at room temperature. The structural and optical properties of nanostructures was characterized by XRD, SEM and UV-Vis techniques. As a result, the CdO nanostructures are oriented along (111) plane of cubic crystal structure. The morphology of CdO nanostructures showed interconnected prism-like and cauliflower-type cluster nanostructure. The UV results of this structures with high absorbtion coefficient are observed to be in accordance with the CdO nanoparticles.     

Photoresponsive poly(methyl methacrylate)2–(polystyrene)2 miktoarm star copolymer containing an azobenzene moiety at the core

We prepared a novel miktoarm star copolymer with an azobenzene unit at the core via combination of atom transfer radical polymerization (ATRP) and nitroxide‐mediated free radical polymerization (NMP) routes. For this purpose, first, mikto‐functional initiator, 3 , with tertiary bromide (for ATRP) and 2,2,6,6‐tetramethylpiperidin‐1‐yloxy (TEMPO) (for NMP) functionalities and an azobenzene moiety at the core was synthesized. The initiator 3 thus obtained was used in the subsequent living radical polymerization routes such as ATRP of MMA and NMP of St, respectively, to give A₂B₂ type miktoarm star copolymer, (PMMA)₂‐(PSt)₂ with an azobenzene unit at the core with controlled molecular weight and low polydispersity (M_w/M_n < 1.15). The photoresponsive properties of 3 and (PMMA)₂‐(PSt)₂ miktoarm star copolymer were investigated. © 2006 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 44: 1396–1403, 2006