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Jesús Sanz - One of the best experts on this subject based on the ideXlab platform.
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Modeling Ti/Ge Distribution in LiTi2–xGex(PO4)3 NASICON Series by 31P MAS NMR and First-Principles DFT Calculations
Journal of the American Chemical Society, 2016Co-Authors: Virginia Diez-gómez, K. Arbi, Jesús SanzAbstract:Ti/Ge distribution in rhombohedral LiTi2–xGex(PO4)3 NASICON series has been analyzed by 31P magic-angle spinning nuclear magnetic resonance (MAS NMR) spectroscopy and first-principles density functional theory (DFT) calculations. Nuclear magnetic resonance is an excellent probe to follow Ti/Ge disorder, as it is sensitive to the atomic scale environment without long-range periodicity requirements. In the samples considered here, PO4 units are surrounded by four Ti/Ge octahedra, and then, five different components ascribed to P(OTi)4, P(OTi)3(OGe), P(OTi)2(OGe)2, P(OTi)(OGe)3, and P(OGe)4 environments are expected in 31P MAS NMR spectra of R3c NASICON samples. However, 31P MAS NMR spectra of analyzed series display a higher number of signals, suggesting that, although the overall symmetry remains R3c, partial substitution causes a local decrement in symmetry. With the aid of first-principles DFT calculations, 10 detected 31P NMR signals have been assigned to different Ti4–nGen arrangements in the R3 subg...
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modeling ti ge distribution in liti2 xgex po4 3 nasicon series by 31P MAS NMR and first principles dft calculations
Journal of the American Chemical Society, 2016Co-Authors: Virginia Diezgomez, K. Arbi, Jesús SanzAbstract:Ti/Ge distribution in rhombohedral LiTi2–xGex(PO4)3 NASICON series has been analyzed by 31P magic-angle spinning nuclear magnetic resonance (MAS NMR) spectroscopy and first-principles density functional theory (DFT) calculations. Nuclear magnetic resonance is an excellent probe to follow Ti/Ge disorder, as it is sensitive to the atomic scale environment without long-range periodicity requirements. In the samples considered here, PO4 units are surrounded by four Ti/Ge octahedra, and then, five different components ascribed to P(OTi)4, P(OTi)3(OGe), P(OTi)2(OGe)2, P(OTi)(OGe)3, and P(OGe)4 environments are expected in 31P MAS NMR spectra of R3c NASICON samples. However, 31P MAS NMR spectra of analyzed series display a higher number of signals, suggesting that, although the overall symmetry remains R3c, partial substitution causes a local decrement in symmetry. With the aid of first-principles DFT calculations, 10 detected 31P NMR signals have been assigned to different Ti4–nGen arrangements in the R3 subg...
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31P MAS-NMR study of R′xR″yP6O18.nH2O cyclohexaphosphates
Journal of Alloys and Compounds, 2001Co-Authors: C Ben Nasr, Mohamed Rzaigui, Isabel Sobrados, Jesús SanzAbstract:Abstract Several alkali/alkaline-earth R x + R y 2+ P 6 O 18 .nH 2 O cyclohexaphosphates, with R + =Li, Na, K, Cs, NH 4 , Tl, DBA; R 2+ =Ca, Zn, Cd, have been analyzed by 31 P MAS-NMR spectroscopy. From their NMR spectra, the number and the multiplicity of crystallographic sites have been analyzed and compared with those deduced by symmetry considerations from X-ray diffraction data. A linear dependence of the isotropic chemical shift values of NMR components on the POP angles of cycles has been obtained. However, some influence of the charge and polarizing strength of alkali and alkaline-earth cations has also been detected. Finally, principal values of the chemical shift tensor of P atoms have been analysed in terms of local symmetry and tetrahedral ring distortions.
Roel Prins - One of the best experts on this subject based on the ideXlab platform.
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31P MAS NMR and Raman study of a Co(Zn)MoP/γ-Al2O3 HDS catalyst precursor containing triethylene glycol
Journal of Catalysis, 2005Co-Authors: Daniele Nicosia, Roel PrinsAbstract:Abstract The effect of triethylene glycol on phosphate-doped Co(Zn)Mo catalysts supported on γ-Al2O3 was studied by means of 31P magic angle spinning nuclear magnetic resonance (MAS NMR) and Raman spectroscopy. 31P MAS NMR experiments, carried out on ZnMo/γ-Al2O3 doped with phosphate and triethylene glycol, suggested that the P 2 Mo 5 O 23 6 − species that formed in the impregnation solution decomposed to monophosphate and an Anderson-type aluminum molybdate species on contact with the support. The presence of triethylene glycol favored the formation of polyphosphate and PMo 12 O 40 3 − heteropolymolybdate species, but no P 2 Mo 5 O 23 6 − was detected. The use of paramagnetic cobalt instead of zinc cations had a paramagnetic effect on the 31P-NMR signal of the PMo 12 O 40 3 − , indicating that the PMo 12 O 40 3 − species are bound to the promoter atoms. The close proximity of the promoter and Mo allows a better decoration of MoS2 and improves the catalytic activity.
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31P MAS NMR and raman study of a co zn mop γ al2o3 hds catalyst precursor containing triethylene glycol
Journal of Catalysis, 2005Co-Authors: Daniele Nicosia, Roel PrinsAbstract:Abstract The effect of triethylene glycol on phosphate-doped Co(Zn)Mo catalysts supported on γ-Al2O3 was studied by means of 31P magic angle spinning nuclear magnetic resonance (MAS NMR) and Raman spectroscopy. 31P MAS NMR experiments, carried out on ZnMo/γ-Al2O3 doped with phosphate and triethylene glycol, suggested that the P 2 Mo 5 O 23 6 − species that formed in the impregnation solution decomposed to monophosphate and an Anderson-type aluminum molybdate species on contact with the support. The presence of triethylene glycol favored the formation of polyphosphate and PMo 12 O 40 3 − heteropolymolybdate species, but no P 2 Mo 5 O 23 6 − was detected. The use of paramagnetic cobalt instead of zinc cations had a paramagnetic effect on the 31P-NMR signal of the PMo 12 O 40 3 − , indicating that the PMo 12 O 40 3 − species are bound to the promoter atoms. The close proximity of the promoter and Mo allows a better decoration of MoS2 and improves the catalytic activity.
Michel Ménétrier - One of the best experts on this subject based on the ideXlab platform.
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Direct Correlation between the 31P MAS NMR Response and the Electronic Structure of Some Transition Metal Phosphides
The Journal of Physical Chemistry C, 2008Co-Authors: Emilie Bekaert, J. Bernardi, Simeon Boyanov, Laure Monconduit, Marie-liesse Doublet, Michel MénétrierAbstract:A series of binary transition metal phosphides (Ni3P, Ni12P5, Ni2P, Ni5P4, NiP, NiP2, FeP, FeP2, FeP4, VP2, CoP) were investigated by solid state 31P MAS NMR, leading to rather different lineshapes...
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Direct correlation between the 31P MAS NMR response and the electronic structure of some Transition-Metal Phosphides
Journal of Physical Chemistry C, 2008Co-Authors: Emilie Beckaert, J. Bernardi, Simeon Boyanov, Laure Monconduit, Marie-liesse Doublet, Michel MénétrierAbstract:A series of binary transition metal phosphides (Ni3P, Ni12P5, Ni2P, Ni5P4, NiP, NiP2, FeP, FeP2, FeP4, VP2, CoP) were investigated by solid state 31P MAS NMR, leading to rather different lineshapes, shifts, relaxation times, and temperature-dependences. The electronic structures of these compounds were computed using various DFT codes, based either on plane waves PAW potentials (VASP), or on all-electron basis sets in the FPLAPW formalism (Wien2K). Depending on the electronic features of the phosphide, self-interaction corrected formalisms (DFT+U or PBE0 hybrid functional) were also used to reach a better description of the electronic ground state and to establish a correlation with the shape and the nature of the NMR signals. As a result of the analysis, the main categories are diamagnetic compounds (FeP4, NiP2) and metallic ones, either real (VP2) or with some electronic localisation in band tails (Ni12P5, Ni2P, Ni5P4, NiP), or with spin-polarized conduction bands (CoP, FeP). FeP2 appears somewhat ambiguous, both based on the various computational results and on the NMR characteristics. Besides, FeP4 is the only compound for which very clear J couplings resulting from P-P bonds were observed.
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Synthesis, structure refinement and characterisation of a new oxyphosphate Mg0.50TiO(PO4)
Materials Research Bulletin, 2007Co-Authors: Saïd Benmokhtar, Michel Ménétrier, Abdelaziz El Jazouli, S. Krimi, Jean-pierre Chaminade, Pierre Gravereau, Danita De WaalAbstract:A new titanium oxyphosphate Mg0.50TiO(PO4) has been synthesized and characterized by several physical techniques: X-ray diffraction, 31P MAS-NMR, Raman diffusion, infrared absorption and diffuse reflectance spectroscopy...
Todd M. Alam - One of the best experts on this subject based on the ideXlab platform.
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using 31P MAS NMR to monitor a gel phase thermal disorder transition in sphingomyelin cholesterol bilayers
Biochimica et Biophysica Acta, 2008Co-Authors: Alison L. Costello, Todd M. AlamAbstract:Abstract The impact of low cholesterol concentrations on an egg sphingomyelin bilayer is investigated using 31P magic angle spinning (MAS) NMR spectroscopy. The magnitude of the isotropic 31P MAS NMR line width is used to monitor the main gel to liquid crystalline phase transition, along with a unique gel phase pretransition. In addition, the 31P chemical shift anisotropy (CSA) and spin–spin relaxation times (T2), along with the effects of spinning speed, proton decoupling and magnetic field strength, are reported. The variation of this unique gel phase thermal pretransition with the inclusion of 5 through 21 mol% cholesterol is presented and discussed.
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Using 31P MAS NMR to monitor a gel phase thermal disorder transition in sphingomyelin/cholesterol bilayers
Biochimica et biophysica acta, 2007Co-Authors: Alison L. Costello, Todd M. AlamAbstract:Abstract The impact of low cholesterol concentrations on an egg sphingomyelin bilayer is investigated using 31P magic angle spinning (MAS) NMR spectroscopy. The magnitude of the isotropic 31P MAS NMR line width is used to monitor the main gel to liquid crystalline phase transition, along with a unique gel phase pretransition. In addition, the 31P chemical shift anisotropy (CSA) and spin–spin relaxation times (T2), along with the effects of spinning speed, proton decoupling and magnetic field strength, are reported. The variation of this unique gel phase thermal pretransition with the inclusion of 5 through 21 mol% cholesterol is presented and discussed.
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Investigation of structure and morphology dynamics in tin fluorophosphate glass - polyethylene hybrids using solid-state 1H, 13C, and 31P MAS NMR
Chemistry of Materials, 2002Co-Authors: B. Tischendorf, Douglas J. Harris, Joshua U. Otaigbe, Todd M. AlamAbstract:The variations in morphology and local structure in a series of tin fluorophosphate glass-polyethylene (TFPPE) hybrids were investigated using solid-state 1H, 13C, and 31P MAS NMR. The combination of direct polarization 13C MAS NMR experiments with various delay times and carbon spin−lattice relaxation filtered cross-polarized MAS NMR experiments allowed quantification of the monoclinic, orthorhombic, amorphous, and intermediate phases in the low-density polyethylene (LDPE) component of the TFPPE hybrids. These 13C MAS NMR results showed an increase in the crystallinity with the addition of tin fluorophosphate (TFP) glass into the hybrids. The 31P MAS NMR spectra reveal major changes in the local structure of the TFP glass component, with several new phosphorus species being formed during the production of the hybrid. The results of the 1H-13C and 1H-31P 2D wide line spectroscopy experiments demonstrate that all of these new phosphorus species are spatially correlated with the two new proton species that ...
Daniele Nicosia - One of the best experts on this subject based on the ideXlab platform.
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31P MAS NMR and Raman study of a Co(Zn)MoP/γ-Al2O3 HDS catalyst precursor containing triethylene glycol
Journal of Catalysis, 2005Co-Authors: Daniele Nicosia, Roel PrinsAbstract:Abstract The effect of triethylene glycol on phosphate-doped Co(Zn)Mo catalysts supported on γ-Al2O3 was studied by means of 31P magic angle spinning nuclear magnetic resonance (MAS NMR) and Raman spectroscopy. 31P MAS NMR experiments, carried out on ZnMo/γ-Al2O3 doped with phosphate and triethylene glycol, suggested that the P 2 Mo 5 O 23 6 − species that formed in the impregnation solution decomposed to monophosphate and an Anderson-type aluminum molybdate species on contact with the support. The presence of triethylene glycol favored the formation of polyphosphate and PMo 12 O 40 3 − heteropolymolybdate species, but no P 2 Mo 5 O 23 6 − was detected. The use of paramagnetic cobalt instead of zinc cations had a paramagnetic effect on the 31P-NMR signal of the PMo 12 O 40 3 − , indicating that the PMo 12 O 40 3 − species are bound to the promoter atoms. The close proximity of the promoter and Mo allows a better decoration of MoS2 and improves the catalytic activity.
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31P MAS NMR and raman study of a co zn mop γ al2o3 hds catalyst precursor containing triethylene glycol
Journal of Catalysis, 2005Co-Authors: Daniele Nicosia, Roel PrinsAbstract:Abstract The effect of triethylene glycol on phosphate-doped Co(Zn)Mo catalysts supported on γ-Al2O3 was studied by means of 31P magic angle spinning nuclear magnetic resonance (MAS NMR) and Raman spectroscopy. 31P MAS NMR experiments, carried out on ZnMo/γ-Al2O3 doped with phosphate and triethylene glycol, suggested that the P 2 Mo 5 O 23 6 − species that formed in the impregnation solution decomposed to monophosphate and an Anderson-type aluminum molybdate species on contact with the support. The presence of triethylene glycol favored the formation of polyphosphate and PMo 12 O 40 3 − heteropolymolybdate species, but no P 2 Mo 5 O 23 6 − was detected. The use of paramagnetic cobalt instead of zinc cations had a paramagnetic effect on the 31P-NMR signal of the PMo 12 O 40 3 − , indicating that the PMo 12 O 40 3 − species are bound to the promoter atoms. The close proximity of the promoter and Mo allows a better decoration of MoS2 and improves the catalytic activity.
