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Giuseppe Bellussi Angela Carati Stefania Guidetti Caterina Rizzo Roberto Millini Stefano Zanardi Erica Montanari Wallace O’Neil Parker Jr. Michela Bellettato 《催化学报》2015,(6):813-819
Phenylene-gallosilicates were prepared with the same crystalline structure as their aluminum ana-logues. The new Ga-Eni Carbon Silicates (Ga-ECS) phases were investigated by X-ray diffraction, scanning electron microscopy, nuclear magnetic resonance and thermogravimetric analysis, which demonstrated that gallium isomorphously replaced aluminum in the framework of the organ-ic-inorganic hybrids similar to the case of classical zeolites. Hybrid ECS materials were obtained with different types of bridged silsesquioxane precursors that maintained the aluminum-silicate nature of the inorganic moiety. This work confirms a new level of crystal chemistry versatility for this class of materials, and demonstrates the possibility to tailor also the inorganic part of the framework by changing the nature of the trivalent heteroatom. 相似文献
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This article revises, analyses, completes and summarizes the crystalline structure of all the Y2Si2O7 and Y2SiO5 polymorphs by combination of diffraction and crystallographic data with spectroscopic MAS-NMR data published up to now. 相似文献
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Sergey N. Britvin Oleg I. Siidra Dr. Sergey V. Krivovichev Wulf Depmeier 《无机化学与普通化学杂志》2009,635(3):518-522
Orange prismatic crystals of the first thallium hydrous nesosilicate Tl4SiO4·0.5H2O have been obtained by evaporation from aqueous solution. There are three symmetrically independent Tl+ cations and five symmetrically independent oxygen atoms in the structure of Tl4SiO4·0.5H2O. The O(4) and O(5) atoms belong to water molecules. Coordination polyhedra of the Tl+ cations are strongly distorted because of the stereoactive behavior of lone electron pairs. The structure of Tl4SiO4·0.5H2O contains sheets of SiO4 tetrahedra and Tl coordination polyhedra. The sheets have the composition [Tl3SiO4]– and are parallel to [100]. Within the sheets, SiO4 tetrahedra link to thallium polyhedra though common corners. The sheets are linked by dimers of face‐sharing Tl(3)O5 polyhedra, thus providing interconnection of the sheets into a framework. The framework has large elliptical channels occupied by water molecules (OW2) and electron pairs of Tl+ cations.The comparison with some other M+ (M = K, Ag, Tl) silicates is given. 相似文献
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Ting Cao Guitang Chen Wancong Lü Han Zhou Jianfu Li Zhaojie Zhu Zhenyu You Yan Wang Chaoyang Tu 《Journal of Non》2009,355(48-49):2361-2364
The photoluminescence properties of silicate glasses, singly doped with europium ions and co-doped with europium ions and Al powder, have been characterized by the absorption, excitation, and emission spectroscopies. The absorption edge in the absorption spectra shows a large red shift from 320 nm to 405 nm. Under near-ultraviolet (NUV) excitation, sample, doped with Eu3+ emit intense red light while those co-doped with Eu3+ and Al give intense cyan emission. The influences of the glass compositions on the spectroscopic properties are also discussed. These glasses may be potential candidates for light-emitting diodes (LEDs). 相似文献
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Ana I. Becerro Alberto Escudero Dominique Massiot 《Journal of solid state chemistry》2004,177(8):2783-2789
This paper describes the 89Y MAS-NMR spectra for all the established polymorphs of Y2Si2O7 (y, α, β, γ and δ) and Y2SiO5 (X1 and X2). The combination of our spectroscopic data with the structural information published up to now from diffraction data permits the revision and correction of mistakes which appear in the literature. Finally, the influence of different structural factors, such as yttrium coordination number and Y-O distances on the 89Y NMR isotropic chemical shift is analyzed. 相似文献
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Raman spectroscopy complimented by infrared spectroscopy has been used to study the mineral hemimorphite from different origins. The Raman spectra show consistently similar spectra with only one sample showing additional bands due to the presence of smithsonite. Raman bands observed at 3510–3565 and 3436–3455 cm−1 are assigned to OH stretching vibrations. Using a Libowitzky type formula, these OH bands provide hydrogen bond distances of 0.2910, 0.2825, 0.2762 and 0.2716 pm. Water bending modes are observed in the Raman spectrum at 1633 cm−1. An intense Raman band at 930 cm−1 is attributed to SiO symmetric stretching vibration of the Si2O7 units. Raman bands observed at 451 and 400 cm−1are attributed to out-of-plane bending vibrations of the Si2O7 units. Raman bands at 330, 280, 168 and 132 cm−1 are assigned to ZnO and OZnO vibrations. 相似文献
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Ab initio band-structure calculations based on the density functional theory have been performed for several crystalline Li, Na, and K-silicates to obtain electric-field gradients (efg) for oxygen atoms. The efg for bridging oxygen environments in these compounds were also investigated by performing ab initio self-consistent field Hartree-Fock molecular orbital calculations on silicate clusters, and there is good agreement between these two approaches. By performing additional ab initio quantum chemistry calculations on model silicate clusters the factors influencing the 17O quadrupole coupling parameters for bridging oxygen environments in alkali silicates have been examined. The quadrupolar asymmetry parameter was found to be dependent on the Si-O-Si angle and the nature of the modifier cation, in agreement with previous studies. In contrast, the quadrupolar coupling constant was found to have a strong dependence on Si-O distance, as well as Si-O-Si angle and the nature of the modifier cation. Analytical expressions describing these dependencies are proposed, which should assist in describing the local environments of bridging oxygen in crystalline and amorphous materials. 相似文献