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31.
Infrared reflectance spectra and the derived absorption spectra of a Na2O-1.41 SiO2 glass and of the parent melt are reported. Polymers with 2 bridging oxygens per silicon (chains) and 3 bridging oxygens (sheets) are identified. Spectra of glass and melt are qualitatively similar. Melt absorption bands show a 10–30 cm?1 shift to lower frequencies. They are broader and less intense than those of the glass which does not agree with Sweet and White's reflectance measurements on similar glass and melt. The small differences between glass and melt can be attributed to the thermal expansion of the medium. 相似文献
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At room temperature and for x0 ~ 0.43, the system Sm1?xLaxAlO3 undergoes a first order phase transition in which an orthorhombic structure transforms into a rhomboedral structure as x increases. This phase transition was investigated by Raman scattering experiments on polycrystalline compounds in the range 0 ? x ? 1. The dependence of low frequency modes on x is reported and compared with their well known temperature dependence. Soft modes have been observed in the orthorhombic (D2h16) and rhomboedral (D3d6) phases. It was found that the first order phase transition is probably driven by a double degenerate mode whose two components in the low symmetry phase display a linear composition dependence of their squared frequencies. The source of anomalous behaviour of Raman bands near the phase transition is discussed. 相似文献
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The profiles of the temperature dependence of TO and LO A2-symmetry mode damping in quartz are calculated by taking into account the actual effect of temperature on the one-phonon density of states. The increase of the population factors of the soft phonons when their frequency falls down to low levels creates, for all other modes, a damping divergence which agrees with that observed experimentally in the vicinity of the α-β phase transition. 相似文献
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Qiang Wang Fabien Lucas Cassandre Quinton Yang-Kun Qu Joëlle Rault-Berthelot Olivier Jeannin Sheng-Yi Yang Fan-Cheng Kong Sarvendra Kumar Liang-Sheng Liao Cyril Poriel Zuo-Quan Jiang 《Chemical science》2020,11(19):4887
In the field of phosphorescent organic light-emitting diodes (PhOLEDs), designing high-efficiency universal host materials for red, green and blue (RGB) phosphors has been quite a challenge. To date, most of the high-efficiency universal hosts reported incorporate heteroatoms, which have a crucial role in the device performance. However, the introduction of different kinds of heterocycles increases the design complexity and cost of the target material and also creates potential instability in the device performance. In this work, we show that pure aromatic hydrocarbon hosts designed with the 9,9′-spirobifluorene scaffold are high-efficiency and versatile hosts for PhOLEDs. With external quantum efficiencies of 27.3%, 26.0% and 27.1% for RGB PhOLEDs respectively, this work not only reports the first examples of high-efficiency pure hydrocarbon materials used as hosts in RGB PhOLEDs but also the highest performance reported to date for a universal host (including heteroatom-based hosts). This work shows that the PHC design strategy is promising for the future development of the OLED industry as a high-performance and low-cost option.In this work, we propose pure hydrocarbon materials as universal hosts for high-efficiency red, green and blue phosphorescent organic light-emitting diodes. 相似文献
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Dr. Lambert Sicard Fabien Lucas Dr. Olivier Jeannin Dr. Pierre-Antoine Bouit Dr. Joëlle Rault-Berthelot Dr. Cassandre Quinton Dr. Cyril Poriel 《Angewandte Chemie (Weinheim an der Bergstrasse, Germany)》2020,132(27):11159-11165
For the last ten years, ring-shaped π-conjugated macrocycles possessing radially directed π-orbitals have been subject to intense research. The electronic properties of these rings are deeply dependent on their size. However, most studies involve the flagship family of nanorings: the cyclo-para-phenylenes. We report herein the synthesis and study of the first examples of cyclofluorenes possessing five constituting fluorene units. The structural, optical and electrochemical properties were elucidated by X-ray crystallography, UV-vis absorption and fluorescence spectroscopy, and cyclic voltammetry. By comparison with a shorter analogue, we show how the electronic properties of [5]-cyclofluorenes are drastically different from those of [4]-cyclofluorenes, highlighting the key role played by the ring size in the cyclofluorene family. 相似文献
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Aluminium fluoroberyllate glasses obtained in the vitreous domain from the quaternary system BaF2CaF2AlF3BeF2 have been studied by Raman spectroscopy. The observed bands have been assigned by comparison with those of cryolite molten aluminofluorides, and of various fluoroberyllates in the crystalline and molten state. The following species have been identified: (AlF4)? tetrahedral groups, (AlF6)?3 octahedral groups polymerized in chains, and a few polymerized species of beryllium fluoride and probably Be2F7?3 dimers. 相似文献
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Dr. Cyril Poriel Dr. Joëlle Rault‐Berthelot Dr. Sébastien Thiery Dr. Cassandre Quinton Dr. Olivier Jeannin Urelle Biapo Dr. Denis Tondelier Bernard Geffroy 《Chemistry (Weinheim an der Bergstrasse, Germany)》2016,22(50):17930-17935
A new electron‐rich fragment, namely the quinolinophenothiazine (QPTZ) is reported. The QPTZ fragment incorporated in spiroconfigured materials leads to higher performance in blue Phosphorescent OLEDs than structurally related phenylacridine and indoloacridine based materials (increasing the HOMO energy level, modulating the spin‐orbit coupling, etc.) and leads to highly efficient blue phosphorescent organic light emitting diodes, indicating the strong potential of this new molecular fragment in organic electronics. 相似文献
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A sensitive and specific determination of benzodiazepines in biological fluids is described, based on reversed-phase high-performance liquid chromatography. The compounds are extracted with a C2 AASP cartridge within 5 min. The recovery ranges from 92 to 104% and is independent of the concentration. Using a suitable gradient elution, complete separation of nineteen benzodiazepines is achieved in 50 min with detection limits of less than 3 ng/ml in urine and 5 ng/ml in other biological fluids. Using a rapid-scanning multichannel detector, the identities of the benzodiazepines can be confirmed. Prazepam is employed as internal standard. The precision and accuracy of the described method are suitable for monitoring benzodiazepine levels in clinical studies and an example is given. 相似文献
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Infrared reflection spectra for the extraordinary ray of zircon and spondumene have been obtained in the frequency range from 270 to 1500 cm?1 and from room temperature up to 1300°K. Using a combination of Kramers-Kronig analysis and a classical dispersion theory, the oscillator parameters of the A2u modes in zircon and Au modes in spodumene were determined. The temperature dependence of observed mode damping is analysed on the basis of quantum theoreticall results involving both cubic and quartic anharmonic contributions. The comparison of the present results with other data reported in previously studied silicate crystals, shows that the observed anharmonic behavior of internal and external modes is consistent with simple considerations based on the site vicinity of each ion. 相似文献