Hydrothermal synthesis, characterization and Raman studies of Eu3+ activated Gd2O3 nanorods

Eu3+ (8 mol%) activated gadolinium oxide nanorods have been prepared by hydrothermal method without and with surfactant, cityl trimethyl ammonium bromide (CTAB). Powder X-ray diffraction (PXRD) studies reveal that the as-formed product is in hexagonal Gd(OH)(3):Eu phase and subsequent heat treatment at 350 and 600 degrees C transforms the sample to monoclinic GdOOH:Eu and cubic Gd2O3:Eu phases, respectively. The structural data and refinement parameters for cubic Gd2O3:Eu nanorods were calculated by the Rietveld refinement. SEM and TEM micrographs show that as-obtained Gd(OH)(3):Eu consists of uniform nanorods in high yield with uniform diameters of about 15 nm and lengths of about 50-150 nm. The temperature dependent morphological evolution of Gd2O3:Eu without and with CTAB surfactant was studied. FTIR studies reveal that CTAB surfactant plays an important role in converting cubic Gd2O3:Eu to hexagonal Gd(OH)(3):Eu. The strong and intense Raman peak at 489 cm(-1) has been assigned to A(g) mode, which is attributed to the hexagonal phase of Gd2O3. The peak at similar to 360 cm(-1) has been assigned to the combination of F-g and E-g modes, which is mainly attributed to the cubic Gd2O3 phase. The shift in frequency and broadening of the Raman modes have been attributed to the decrease in crystallite dimension to the nanometer scale as a result of phonon confinement. (C) 2010 Elsevier B.V. All rights reserved.

Triple resonance, triple-quantum NMR studies of dipolar coupled spin systems

Multiple quantum-single quantum correlation experiments are employed for spectral simplification and determination of the relative signs of the couplings. In this study, we have demonstrated the excitation of three nuclei, triple quantum coherences and discussed the information obtainable from such experiments. The experiments have been carried out on doubly labeled acetonitrile and fluoroacetonitrile aligned in liquid crystalline media. The experiment is advantageous in providing many spectral parameters from a single experiment. The coherence pathways involved in the pulse sequence are described using product operators. (C) 2011 Elsevier Inc. All rights reserved.

SCF and electron correlation studies on structure, force constants and vibrational spectra of borane monoammoniate complex

Effects of basis set and electron correlation on the equilibrium geometry, force constants and vibrational spectra of BH3NH3 have been studied. A series of basis sets ranging from double zeta to triple zeta including polarization and diffuse functions have been utilized. All the SCF based calculations overestimate the dative B-N bond distance and considerable improvement occurs when the treatment for electron correlation is introduced. Detailed vibrational analysis for BH3NH3 has been carried out. The mean absolute percentage deviation of the ab initio predicted vibration frequencies of (BH3NH3)-B-11 from the experiment is about 10% for the SCF based calculations and the MP2 method shows better agreement, the overall deviation being 5-6%. The ground state effective force constants of BH3NH3 were obtained using RECOVES procedure. The RECOVES sets of force constants are found to be highly satisfactory for the prediction of the vibrational frequencies of different isotopomers of BH3NH3. The mean absolute percentage deviation of the calculated frequencies of different isotopomers from the experiment is much less than 1%. The RECOVES-MP2/augDZP set of force constants was found to be the best set among the different sets for this molecule. Theoretical infrared intensities are in fair agreement with the observed spectral features.

Surface studies on uranium monocarbide using XPS and SIMS

The air-exposed surfaces of sintered and are-melted UC samples were examined by XPS and SIMS. XPS results indicate that the surface is covered with a very thin layer of UO2 mixed with free carbon, which would have formed along with the oxide during the reaction between UC and oxygen or moisture. From the SIMS depth profile of oxygen, the thickness of the oxide layer is found to be approximately 10 nm. The SIMS oxygen images of the surface as a function of etching time reveal that the surface of UC consists of a top layer of adsorbed moisture/oxygen; this contamination layer is followed by a layer containing uranium oxide, uranium hydroxide and free carbon and then grain boundary oxide and finally bulk UC. The behaviour of sintered and are-melted samples is similar.

Synthesis and studies on pyridinium chlorofluoro complexes of indium and bismuth

Pyridinium trichlorotrifluoroindate, (C5H5NH)(3)InCl3F3, and pyridinium trichlorofluorobismuthate, C5H5NHBiCl3F, have been synthesised by the reaction of pyridinium poly(hydrogen fluoride), PPHF, with InCI3 and BiCl3, respectively. These new complexes have been characterised by chemical and thermal analysis, NMR (H-1 and F-19) and infrared spectroscopy, and powder X-ray diffraction methods

Thermal expansion studies of substituted CTP derivatives

Several new Na, Y and Zr substituted derivatives of Ca-0.5 Ti-2(PO4)(3) (CTP) have been synthesized. These derivatives retain the hexagonal structure of the parent (CTP) compound with minor changes in lattice parameters. Linear thermal expansion coefficients (alpha) have been obtained using a high sensitivity dilatometer.

1H and 13C NMR spectral studies of conformation of some N-(2-pyridinyl)-3-pyridinecarboxamides

The 1H and 13C NMR spectra of N-(2-pyridinyl)-, N-(4-methyl2-pyridinyl)-, and N-(6-methyl-2-pyridinyl)-3-pyridine-carboxamides (1�3, respectively) and 3-pyridinecarboxamide (4) in different solvents have been analysed using COSY, HETCOR, chemical shift and coupling constant correlations. The conformations of 1�4 have been obtained by utilizing the NMR spectra, NOE experiments and MINDO/3 calculations. In dilute solutions, the 2-pyridyl ring is coplanar with the amide group while the 3-pyridyl ring is apparently not. Compounds 1�3 dimerize through cooperative hydrogen bonding in concentrated CDCl3 solution (approximately 0.1 M) and the structure of the dimer resembles some of the DNA base-pairs. Hydrogen bonding between N---H and the solvent molecules hinders dimerization in (CD3)2CO and CD3CN.

Wavepacket dynamical studies on trans-azobenzene: absorption spectrum and resonance Raman excitation profiles of the n??* transition

Time-dependent wavepacket propagation techniques have been used to calculate the absorption spectrum and the resonance Raman excitation profiles of the n-pi* transition in azobenzene. A comparison of both the calculated absorption spectrum and excitation profiles with experiment has been made. From an analysis of the data, it is concluded that the Raman intensities are mainly due to resonance from the n-pi* transition and not from the pre-resonance of the pi-pi* transition, as reported earlier. We find that the isomerization pathway is through the inversion mechanism rather than by rotation. This is the first direct spectroscopic evidence for the isomerization pathway in trans-azobenzene.

7Li and 23Na NMR studies of transmembrane cation transport mediated by ionophore lasalocid A

Ion transport across phospholipid vesicles was studied by 7Li and 23Na-NMR using an aqueous anionic paramagnetic shift reagent, dysprosium nitrilotriacetate [Dy(NTA)2]3?, mediated by ionophores, lasalocid A and A23187. The intra- and extracellular 7Li and 23Na-NMR signals were well separated (20?Hz) at mM concentration of the shift reagent. The observed data on the rate constant for lithium transport across DPPC vesicles at various concentrations of the ionophores indicated that lasalocid A is a more efficient carrier for lithium ion compared with the sodium ion transport by this ionophore, while A23187 was not specific to either of the ions (Li or Na). ©1998 European Peptide Society and John Wiley & Sons, Ltd.

Proton NMR spectral studies on N-(4-methylphenyl)-2- and 3-pyridinecarboxamides

The H-1 NMR spectra of N-(4-methylphenyl)-2-pyridinecarboxamide and N-(4-methyl-phenyl)-3-pyridine carboxamide in CDCl3 and (CD3)(2)CO have been analysed with the help of the COSY spectra. Accurate H-1 chemical shifts and coupling constants have been obtained from the simulated spectra. From H-1 NMR and Nuclear Overhauser Enhancement (NOE) measurements the molecular conformations are inferred. The pyridyl ring is apparently coplanar with the amide group while the 3-pyridyl ring is nearly perpendicular to the amide plane so that the amide proton is nearer to the 2-pyridyl proton H2 than to H4. The orientation of the 4-methylphenyl group could not be determined.

Optimization studies on limestone beneficiation

Limestone rejects from Bagalkot mines have been beneficiated by froth flotation with a view to reducing the magnesia content. In order to ascertain the effect of the main parameters such as sodium oleate concentration, sodium silicate concentration and pH on the MgO content, statistically designed experiments have been performed. The results indicate that under the optimum conditions arrived at limestone rejects could be beneficiated to produce a concentrate with magnesia. content meeting the specifications for cement manufacture.

Preliminary studies on the synthesis and characterisation of hydroxyapatites

Synthesis of calcium hydroxyapatite Ca-10(PO4)(6)(OH)(2) ceramic powders by a solid state reaction between commercially available tricalcium phosphate and calcium hydroxide powders has been attempted in the range 700-1000 degrees C. Reaction of tricalcium phosphate and calcium hydroxide in 3:2 molar ratio at 1000 degrees C leads to the formation of pure calcium hydroxyapatite phase. The sample has been characterised by XRD and IR spectral studies. The compacted powder is sintered to 93% of theoretical density when fired in air at 1300 degrees C for 2 hours.

Structural studies of protein unfolding

Methods for macromolecular structure determination (NMR and crystallography) are now being used to get structural information on partially folded and unfolded states of proteins. These techniques, in combination with proton hydrogen exchange studies are powerful tools to extract information on non-native states of proteins. This review discusses progress In this area of protein folding.

Studies of interfaces in Al-65 Cu20Fe15

The study of interfaces in quasicrystalline alloys is relatively new. Apart From the change in orientation, symmetry and chemistry which can occur across homophase and heterophase boundaries in crystalline materials, we have the additional, exciting possibility of an interface between quasicrystalline and its rational approximant. High resolution electron microscopy is a powerful technique to study the structural details of such interfaces. We report the results of a HREM study of the interface between the icosahedral phase and the related Al13Fe4 type monoclinic phase in melt spun and annealed Al65Cu20Fe15 alloy.

Studies on adsorption of guar gum onto biotite mica

The interaction of guar gum with biotite mica has been investigated through adsorption, flotation and electrokinetic measurements. The adsorption densities of guar gum increase with increase of pH and the isotherms exhibit Langmuirian behaviour. Pretreatment of mica with a complexing agent such as EDTA results in a decrease in the adsorption density, highlighting the contribution of metal ions to the adsorption process. An increase in the surface face-to-edge ratio lends to an increase in the adsorption density. The flotation recoveries decrease as a function of pH, complementing the adsorption results. However, polymer depressant ability is reduced in the case of EDTA treated mica, consequent to reduction of metallic sites. Electrokinetic measurements portray conformational rearrangements of macromolecules with the loading, resulting in the shift of the shear plane, further away from the interface. Dissolution experiments indicate release of metal ions from mica, while co-precipitation tests confirm polymer-metal ion interaction in the bulk solution. The adsorption process is governed by hydrogen bonding as well as chemical interaction between guar gum and the surface metal hydroxide groups of mica. (C) 1997 Published by Elsevier Science Ltd.