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Search: WFRF:(Lantto V)

  • Result 1-35 of 35
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1.
  • Gowda, Vasantha, et al. (author)
  • Structural investigations of rare earth dialkyl dithiocarbamate complexes: solid-state NMR, X-ray diffraction and DFT calculation studies
  • 2013
  • Conference paper (other academic/artistic)abstract
    • In this study, we made an attempt to qualitatively study the structures of few rare earth metal complexes by employing solid state NMR, X-Ray Diffraction, and preliminary DFT calculations. High resolution 13C and 15N solid state CP/MAS NMR spectra were recorded for six diamagnetic polycrystalline rare earth dialkyldithiocarbamates of the general formula [(RE2S2CNR2)3 PHEN] (where RE=La or Y, R=C2H5, C3H7, and i-C3H7) [1]. Different isotropic 13C and 15N chemical shifts for the three dialkyldithiocarbamato groups were observed. Regulacio et al. (2005) inferred that irrespective of the alkyl chains, rare earth complexes of dialkyldithiocarbamates and phenanthroline (3:1) ligands always crystallize in a monoclinic system with a space P21/c group. However, comparative analysis of solid state 13C/15N CPMAS spectra of polycrystalline yttrium and lanthanum diethyldithiocarbamate complexes shows the presence of significant differences, indicating structural variations of these complexes. Also, quite different X-Ray diffraction powder pattern was observed for the above two complexes. Finally, the computational geometry optimization of Y and La complexes, followed by the preliminary calculation of 13C and 15N chemical shifts and shielding contributions with the ADF program [2], found to be very near to the experimental results.
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  • Roukala, Juho, et al. (author)
  • Experimental and First-Principles NMR Analysis of Pt(II) Complexes With O,O'-Dialkyldithiophosphate Ligands
  • 2016
  • In: Journal of Physical Chemistry A. - : American Chemical Society (ACS). - 1089-5639 .- 1520-5215. ; 120:42, s. 8326-8338
  • Journal article (peer-reviewed)abstract
    • Polycrystalline bis(dialkyldithiophosphato)Pt(II) complexes of the form [Pt{S2P(OR)2}2] (R = ethyl, iso-propyl, iso-butyl, sec-butyl or cyclo-hexyl group) were studied using solid-state 31P and 195Pt NMR spectroscopy, to determine the influence of R to the structure of the central chromophore. The measured anisotropic chemical shift (CS) parameters for 31P and 195Pt afford more detailed chemical and structural information, as compared to isotropic CS and J couplings alone. Advanced theoretical modeling at the hybrid DFT level, including both crystal lattice and the important relativistic spin-orbit effects qualitatively reproduced the measured CS tensors, supported the experimental analysis, and provided extensive orientational information. A particular correction model for the non-negligible lattice effects was adopted, allowing one to avoid a severe deterioration of the 195Pt anisotropic parameters due to the high requirements posed on the pseudopotential quality in such calculations. Though negligible differences were found between the 195Pt CS tensors with different substituents R, the 31P CS parameters differed significantly between the complexes, implying the potential to distinguish between them. The presented approach enables good resolution and a detailed analysis of heavy-element compounds by solid-state NMR, thus widening the understanding of such systems.
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  • Frantti, J., Ivanov, S. A., Eriksson, S.- G., Rundlöf, H., Lantto,V.Lappalainen, J. and Kakihana, M. (author)
  • On the phase transitions of Pb(ZrxTi1
  • 2002
  • In: Phys. Rev.. ; B66, s. 64108-
  • Journal article (peer-reviewed)
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  • Frantti, J., Ivanov, S., Eriksson, S., Rundlöf, H., Lantto, V., Lappalainen, J. and Kakihana, M. (author)
  • Phase transitions of Pb(ZrxTi1
  • 2002
  • In: Phys. Rev.. ; B66, s. 64108-
  • Journal article (peer-reviewed)
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  • Frantti, J, et al. (author)
  • Local and average structure of lead titanate based ceramics
  • 2002
  • In: Ferroelectrics. - : Informa UK Limited. - 0015-0193 .- 1563-5112. ; 266:1, s. 73-90
  • Journal article (peer-reviewed)abstract
    • The revised lattice dynamics of Pb(Zr x Ti 1 -x )O 3 (PZT) with 0.10 ≤ x ≤0.54 ceramics is reported. The phase transition from tetragonal phase to the monoclinic phase is proposed to occur via locally distorted regions. Neutron diffraction data suggests that these local regions transform to the monoclinic phase with decreasing temperature, when x ≈0.50.
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  • Frantti, J, et al. (author)
  • Neutron diffraction studies of Pb(ZrxTi1-x)O-3 ceramics
  • 2000
  • In: JAPANESE JOURNAL OF APPLIED PHYSICS PART 1-REGULAR PAPERS SHORT NOTES & REVIEW PAPERS. - : INST PURE APPLIED PHYSICS. - 0021-4922. ; 39:9B, s. 5697-5703
  • Journal article (peer-reviewed)abstract
    • Neutron diffraction studies of lead zirconate titanate Pb(ZrxT1-x)O-3 (PZT) powders, 0.20 less than or equal to x less than or equal to 0.54, were carried out at 10 K and 297 K, The phase transition predicted by our earlier Raman observations (J. Frantti,
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  • Frantti, J, et al. (author)
  • Raman scattering study of the Pb(HfxTi1-x)O-3 ceramics
  • 2005
  • In: Journal of Electroceramics. - 1573-8663 .- 1385-3449. ; 13, s. 299-303
  • Journal article (peer-reviewed)abstract
    • Raman spectroscopy was used to study the long wavelength vibrations of tetragonal perovskite (space group P4mm) Pb(HfxTi1-x)O-3 (PHT) (0.10 less than or equal to x less than or equal to 0.50) samples at room temperature and at approximate to 20 K. For x less than or equal to 0.40, Raman spectra collected from the PHT samples were very similar to the previous spectra collected from the PZT samples with the same value of x, except the mode at around 190 cm(-1) whose frequency was decreasing with increasing x in PHT ceramics. Correspondingly, the latter feature was taken as a sign of the 'mass effect' (Hf versus Zr) while the similarity of the remaining parts of the Raman spectra was assumed to be due to the almost identical ionic radii difference between Ti4+ and Zr4+ and between Ti4+ and Hf4+ ionic radii. The behaviour of the mode at around 280 cm(-1) revealed that a phase transition occurred once x was changing from 0.40 to 0.50.
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  • Gowda, Vasantha, et al. (author)
  • Structural insights into the polymorphism of bismuth(III) di-n-butyldithiocarbamate by X-ray diffraction, solid-state (13C/15N) CP-MAS NMR and DFT calculations
  • 2017
  • In: Polyhedron. - : Elsevier. - 0277-5387 .- 1873-3719. ; 129, s. 123-132
  • Journal article (peer-reviewed)abstract
    • Two crystalline polymorphs of a binuclear tris(di-n-butyldithiocarbamato)bismuth(III) complex, I and II, with an empirical formula of [Bi{S2CN(n-C4H9)2}3] were synthesised and characterised by X-ray diffraction (XRD), solid-state NMR and density functional theory (DFT) calculations. At the supramolecular level, these mononuclear molecular units interact in pairs via secondary Bi⋯S bonds, yielding binuclear formations of [Bi2{S2CN(n-C4H9)2}6]. The polymorph I () contains two isomeric non-centrosymmetric binuclear molecules of [Bi2{S2CN(n-C4H9)2}6], which are related to each other as conformers, therefore having four structurally inequivalent bismuth atoms and twelve inequivalent dithiocarbamate ligands. In contrast, the structurally simpler polymorph II (P21/n) exists as a single molecular form of the corresponding centrosymmetric binuclear formation, comprising two structurally equivalent bismuth atoms and three structurally different dithiocarbamate groups. The polymorphs I and II were found to be interconvertible by altering the solvent system during the recrystallisation process. Sun et al. (2012) has reported a crystalline form of the title compound which resembles, but is not identical with, polymorph II. Experimental solid-state 13C and 15N cross-polarisation (CP) magic-angle-spinning (MAS) NMR spectra of both polymorphs I and II were in accord with the direct structural data on these complexes. Assignments of the resonance lines in the solid-state 13C and 15N NMR spectra were assisted by chemical shift calculations of the crystals using periodic DFT.
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  • Kish, L.B., Solis, J.L., Vajtai, R., Granqvist, C.G., Olsson, J., Schnurer, J., Lantto, V., Marlow, W.H., Gingl, Z. (author)
  • How can noise “smell” and remember that “smell”
  • 2001
  • In: 16th International Conference on Noise in Physical Systems and 1/f Fluctuations, Gainesville Florida, October 22-25, 2001. Paper to be presented by L.B. Kish..
  • Conference paper (other academic/artistic)
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  • Reyes, L. F., et al. (author)
  • Gas sensor response of pure and activated WO3 nanoparticle films made by advanced reactive gas deposition
  • 2006
  • In: Sensors and actuators. B, Chemical. - : Elsevier BV. - 0925-4005 .- 1873-3077. ; 117:1, s. 128-134
  • Journal article (peer-reviewed)abstract
    • Pure and activated (doped) nanocrystalline WO3 films, produced by advanced reactive gas deposition, were investigated for gas sensing applications. Activation took place by co-evaporation of Al or Au with tungsten oxide as the particles were produced. Structural characterization of the films was performed by electron microscopy and X-ray diffractometry. Sensitivity, response time, and recovery time of the sensors were systematically investigated as a function of annealing and operating temperature, using H2S, CO, and NO, as test gases. The sensitivity was found to lie below and around the ppm level for H2S and NO2, respectively.
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  • Solis, J. L., et al. (author)
  • Identifying natural and artificial odours through noise analysis with a sampling-and-hold electronic nose
  • 2001
  • In: Sensors and actuators. B, Chemical. - : Elsevier. - 0925-4005 .- 1873-3077. ; 77:1-2, s. 312-315
  • Journal article (peer-reviewed)abstract
    • A sampling-and-hold type electronic nose was used to investigate "frozen" sensor dynamics. The sensor was heated to the sensing temperature and exposed to a chemical environment for a short time. Then, while keeping the sensor in the chemical environment, the heating was switched off so that the sensor cooled down to room temperature. Chemicals species become trapped in the sensor film, and therefore, the current transport in the film is changed. The trapped chemicals are usually located at grain boundaries, and they influence the charge transport in the grains and between the grains. This gives random fluctuations to the local conductivity. Resistance noise was employed to extract chemical information from the sensor in the cold state.
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32.
  • Solis, JL, et al. (author)
  • Nanocrystalline tungsten oxide thick-films with high sensitivity to H2S at room temperature
  • 2001
  • In: SENSORS AND ACTUATORS B-CHEMICAL. - : ELSEVIER SCIENCE SA. - 0925-4005. ; 77:1-2, s. 316-321
  • Journal article (peer-reviewed)abstract
    • Ultra-fine powder of tungsten oxide was made by evaporation of tungsten metal by an electric are discharge in a reactive atmosphere. The obtained WO3 powder displayed a mixture of monoclinic and tetragonal phases and had a mean grain size of 40 nm. We inv
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33.
  • Solis, JL, et al. (author)
  • Semiconductor gas sensors based on nanostructured tungsten oxide
  • 2001
  • In: THIN SOLID FILMS. - : ELSEVIER SCIENCE SA. - 0040-6090. ; 391:2, s. 255-260
  • Journal article (peer-reviewed)abstract
    • Semiconductor gas sensors based on nanocrystalline WO3 films were produced by two different methods. Advanced reactive gas evaporation was used in both cases either for a direct deposition of films (deposited films) or to produce ultra fine WO3 powder whi
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34.
  • Solis, JL, et al. (author)
  • Structure characterization of semiconducting tin and tungsten mixed oxides
  • 1999
  • In: PHYSICA SCRIPTA. - : ROYAL SWEDISH ACAD SCIENCES. - 0281-1847. ; T79, s. 216-219
  • Journal article (other academic/artistic)abstract
    • Mixed-oxide powders of tin and tungsten were made by heating various mixtures of SnO and WO3 powders, corresponding to the nominal formula SnxWO3+x with x between 0.5 and 2.0, in an argon atmosphere at 600 degrees C for 15 hours. The alpha-SnWO4 phase was
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35.
  • Solis, JL, et al. (author)
  • Synthesis of new compound semiconductors in the Sn-W-O system for gas-sensing studies
  • 2000
  • In: SENSORS AND ACTUATORS B-CHEMICAL. - : ELSEVIER SCIENCE SA. - 0925-4005. ; 68:1-3, s. 286-292 Language: English
  • Journal article (peer-reviewed)abstract
    • Screen printing has been used to fabricate thick films of various compound and mixed oxides in the Sn-W-O system for gas-sensing studies. The powders for the thick-film pastes were made by heating in vacuum various mixtures of SnO and WO3 powders, corresp
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  • Result 1-35 of 35

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