Microwave-assisted hydrothermal synthesis of structurally and morphologically controlled sodium niobates by using niobic acid as a precursor

There are many advantages to using a microwave as a source of heat in hydrothermal reactions. Because it is a quick and homogeneous way to crystallize ceramic powders, it was used in this work for the production of antiferroelectric sodium mobate (NaNbO3) in a cubic-like form and its intermediary phase, disodium diniobate hydrate (Na2Nb2O6 center dot H2O), with a fiber morphology. The syntheses were carried out by treating niobic acid (Nb2O5 center dot nH(2)O) with NaOH. By changing the reaction time and the concentration of the reactants, particles with different structures and different morphologies could be obtained. The structural evolution of the products of this reaction was elucidated on the basis of the arrangement of the NbO6 octahedral units. Conclusive results were obtained with morphological and structural characterizations through XRD, TEM, MEV, and NMR and Raman spectroscopy. ((C) Wiley-VCH Verlag GmbH & Co. KGaA, 69451 Weinheim, Germany, 2008).

Crystal Structure Determination of Mebendazole Form A Using High-Resolution Synchrotron X-Ray Powder Diffraction Data

Fundação de Amparo à Pesquisa do Estado de São Paulo (FAPESP)

Crystal structure of propylthiouracil determined using high-resolution synchrotron X-ray powder diffraction

Fundação de Amparo à Pesquisa do Estado de São Paulo (FAPESP)

Relationship between grain-boundary capacitance and bulk shallow donors in SnO2 polycrystalline semiconductor

The relationship between grain-boundary capacitance and extrinsic shallow donors caused by Nb addition to SnO2 center dot COO binary polycrystalline system has been investigated by means of combined techniques such as I-V characteristic response, complex impedance and capacitance analysis and electrostatic force microscopy. The estimated role of the Nb doping is to increase the concentration of shallow donors that are capable of enhancing the electronic donation to grain-boundary acceptors. This effect leads to the formation of potential barriers at grain boundaries with a simultaneous increase of grain-boundary capacitance and non-Ohmic features of the polycrystalline device doped with Nb atoms.

Synchrotron structural characterization of electrochemically synthesized hexacyanoferrates containing K(+): A revisited analysis of electrochemical redox

The presumably soluble KFe(+3)[Fe(2+)(CN)(6)] structure of electrochemically synthesized hexacyanoferrate materials (Prussian Blue) containing K(+) ions was determined for the first time in this study. Prior to drawing conclusions from a structural analysis, the main goal was to make a precise analysis of the inferred soluble structure, that is, KFe(+3) [Fe(2+)(CN)(6)], which is frequently referred to in the literature as the final stable electrochemically synthesized structure. Indeed, a successful X-ray powder diffraction experiment using X-ray synchrotron radiation was made of a powder placed in a 0.5 mm diameter borosilicate glass capillary, which was obtained by removing sixty 90 nm thin films from the substrates on which they were prepared. However, the conclusions were highly unexpected, because the structure showed that the [Fe(CN)61 group was absent from similar to 25% of the structure, invalidating the previously presumed soluble KFe(+3)[Fe(2+)(CN)(6)] structure. This information led to the conclusion that the real structure of Prussian Blue electrochemically synthesized after the stabilization process is Fe(4)[Fe(CN)(6)](3)center dot mH(2)O containing a certain fraction of inserted K(+) ions. In fact, based on an electrogravimetric analysis (Gimenez-Romero et al., J. Phys. Chem. B 2006, 110, 2715 and 19352) complemented by the Fourier maps. it is possible to affirm that the K(+) was part of the water crystalline substructure. Therefore, the interplay mechanism was reexamined considering more precisely the role played by the water crystalline substructure and the K+ alkali metal ion. As a final conclusion, it is proposed that the most precise way to represent the structure of electrochemically synthesized and stabilized hexacyanoferrate materials is Fe(4)(3+) Fe(2+)(CN)(6)](3)center dot[K(h)(+)center dot OH(h)(-)center dot mH(2)O]. The importance of this result is that the widespread use of the terms soluble and insoluble in the electrochemical literature could be reconsidered. Indeed, only one type of structure is insoluble, and that is Fe(4)[Fe(CN)(6)](3)center dot mH(2)O hence, the use of the terms soluble and insoluble is inappropriate from a structural point of view. The result of the presence of the [Fe(CN)61 vacancy a, roup is that the water Substructure cannot be ignored in the ionic interplay mechanism which controls the intercalation and redox process, as was previously confirmed by electrogravimetric analyses (Gimenez-Romero et al., J. Phys. Chem. B 2006, 110, 2715 Garcia-Jareno et al., Electrochim. Acta 1998, 44, 395: Kulesza, Inorg. Chem. 1990, 29, 2395).

Ion-sensing properties of 1D vanadium pentoxide nanostructures

Coordenação de Aperfeiçoamento de Pessoal de Nível Superior (CAPES)

Studies of the Electrochemical Degradation of Acetaminophen Using a Real-Time Biomimetic Sensor

Fundação de Amparo à Pesquisa do Estado de São Paulo (FAPESP)

Feasibility of internal standardization in the direct and simultaneous determination of As, Cu and Pb in sugar-cane spirits by graphite furnace atomic absorption spectrometry

Fundação de Amparo à Pesquisa do Estado de São Paulo (FAPESP)

Thermal Behavior of Sr(II) and Ba(II)-Diclofenac Complexes in Solid State: Study of the Dehydration and Thermal Decomposition

Coordenação de Aperfeiçoamento de Pessoal de Nível Superior (CAPES)

Re-examination of the anion derivatives of isoflavones by radical fragmentation in negative electrospray ionization tandem mass spectrometry: experimental and computational studies

Fundação de Amparo à Pesquisa do Estado de São Paulo (FAPESP)

Synthesis, spectral and thermal studies on dicarboxylate-bridged palladium(II) coordination polymers. Part II

The synthesis and thermal behavior of the new [Pd(fum)(bipy)] (n) center dot 2nH(2)O (1), [Pd(fum)(bpe)] (n) center dot nH(2)O (2) and [Pd(fum)(pz)] (n) center dot 3nH(2)O (3) {bipy = 4,4'-bipyridine, bpe = 1,2-bis(4-pyridyl)ethene and pz = pyrazine} fumarate complexes are described in this work as well their characterization by IR and (13)C CPMAS NMR spectroscopies. TG curves showed that the compounds released organic ligands and lattice water molecules in the temperature range of 46-491 A degrees C. In all the cases, metallic palladium was identified as the final residue.

(-)-Kolavenic acid

In the two, almost identical, molecules in the asymmetric unit of the title compound [ systematic name: (E)-3-methyl-5-(1,2,4a, 5-tetramethyl-1,2,3,4,4a,7,8,8a-octahydronaphthalen-1yl) pent-2-enoic acid], C20H32O2, the rings are trans fused. The cyclohexane ring has a chair conformation and the cyclohexene ring a distorted half-boat conformation. The two independent molecules are connected into a dimer via O-H center dot center dot center dot O hydrogen bonds. The dimers are associated into supramolecular chains along c via C-H center dot center dot center dot O contacts.

Iron chelating-mediated antioxidant activity of Plectranthus barbatus extract on mitochondria

Fundação de Amparo à Pesquisa do Estado de São Paulo (FAPESP)

Synthesis and characterization of a new platinum(II) complex with L-mimosine

Synthesis and characterization of a new Pt(II)-mimosine complex are described. Elemental, mass spectrometry and thermal analyses for the complex are consistent with the formula [PtCl2(C8H10N2O4)]center dot 1.5H(2)O. C-13 NMR, N-15 NMR and infrared spectroscopy indicate coordination of the ligand to Pt(II) through the N and O atoms in a square-planar geometry. The final residue after thermal treatment was identified as metallic Pt. The complex is soluble in dimethylsulfoxide.

Synthesis, spectroscopic characterization and biological analysis of a new palladium(II) complex with methionine sulfoxide

A new palladium(II) complex with methionine sulfoxide was synthesized and characterized by a set of chemical and spectroscopic techniques. Elemental and mass spectrometry analyses of the solid complex fit to the composition [Pd(C5H10NO3S)(2)]center dot H2O. C-13 NMR, [H-1-N-15] NMR and infrared spectra indicate coordination of the amino acid to Pd(II) through the carboxylate and amino groups in a square planar geometry. The complex is soluble in water.Biological activity was evaluated by cytotoxic analysis using HeLa cells. Determination of cell death was assessed using a tetrazolium salt colorimetric assay, which reflects the cells viability. After incubation for 48 h, 20% of cell death was achieved at a concentration of 200 mu mol L-1 of the complex. (c) 2006 Elsevier B.V. All rights reserved.