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The concentration of reactive metal hydride (Met-H) reducing agents can be determined (in < or = 20 min) using No-D NMR spectroscopy. The method involves (i) reacting Met-H with an excess of p-methoxybenzaldehyde, (ii) quenching with excess acetic acid, (iii) recording the No-D NMR spectrum of this homogeneous mixture, and (iv) deducing the concentration of Met-H from the % conversion (as measured by integration). By a conceptually related method, the titer of the basic alkali metal hydrides KH and NaH can also be determined. 相似文献
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The preparation of macrocyclic 7,19-dibenzyl-7,19-diaza-1,4,10,13,16-pentaoxa-cycloheneicosane-6, 20-diones substituted in positions 2 and 3 with methyl groups, and their properties in PVC membranes as calcium sensors are described. Complexes of these polyether diamides (PEDA) with calcium and tetra(4-chlorophenyl)borate (TClPB) ions having the composition 2PEDA·Ca·2TClPB were prepared. Calcium electrodes based on these complexes have selectivity coefficients for calcium over barium up to 103, and over alkali metals up to 3 × 104. 相似文献
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[reaction: see text] The title technique is a convenient and powerful method for directly monitoring or assaying any reaction mixture or reagent solution. Examples of some common processes (Fischer esterification, lithiation, butyllithium/THF compatibility, olefin metathesis, and a quantification assay), each interrogated in its native solvent, are presented. The spectral data are easy to acquire, and the information content makes a compelling case for routine use of No-D NMR spectroscopy. 相似文献
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Oblatum 5-XII-1991 & 24-II-1993 相似文献
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A miniature version of the potassium ion-selective electrode with valinomycin or dimethyldibenzo-30-crown-10 in a poly(vinyl chloride) matrix is described. Electrodes having an effective membrane area of <0.2 mm(2) exhibit Nernstian behaviour within a range of activities of the potassium ion of 10(-1)-10(-5)M, a rapid response and good long-term potential stability. 相似文献
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F. Soška F. Beneš S. Jura B. Gross Z. šimša F. Kosek J. Horák J. Kašpar K. čermák J. Lipták M. Ryba E. F. Holländer A. Havránek E. Havránková A. Kochanovská J. Sommer F. Vilím P. Lukáš C. Rumler S. Kadečková F. Vávra M. Matyáš J. Beneš J. Kučera L. DvoŘák Z. KudĚlásek J. Hájek A. Marek Z. Malec J. Janků B. Sojka L. Karmazin M. Ryšavá L. Janko K. Huml 《Czechoslovak Journal of Physics》1961,11(11):852-862
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Rafal Nowaczynski Marcin Gajc Hancza B. Surma Pawel Osewski Adam Strzep Witold Ryba‐Romanowski Dorota A. Pawlak 《Particle & Particle Systems Characterization》2019,36(1)
Quantum dot (QD)‐based light‐emitting materials are gaining increased attention because of their easily tunable optical properties desired for various applications in biology, optoelectronics, and photonics. However, few methods can be used to manufacture volumetric materials doped with more than one type of QD other than QD‐polymer hybrids, and they often require complicated preparation processes and are prone to luminescence quenching by QD aggregation and separation from the matrix. Here, simultaneous doping of a volumetric glass‐based nanocomposite with two types of QDs is demonstrated for the first time in a single‐step process using the nanoparticle direct doping method. Glass rods doped with CdTe, CdSe/ZnS, or co‐doped with both QDs, are obtained. Photoluminescence and lifetime experiments confirm temperature‐dependent double emission with maxima at 596 and 720 nm with mean lifetimes up to 16 ns, as well as radiative energy transfer from the short wavelength–emitting QDs to the long wavelength–emitting QDs. This approach may enable the simple and cost‐efficient manufacturing of bulk materials that produce multicolor luminescence with cascade excitation pumping. Applications that could benefit from this include broadband optical fiber amplifiers, backlight systems in LCD screens, high‐power LEDs, or down‐converting solar concentrators used to increase the efficiency of solar panels. 相似文献
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P. Solarz M. Nikl A. Kos R. Lisiecki W. Ryba‐Romanowski A. Rzepka S. Ganschow A. Pajczkowska 《Crystal Research and Technology》2007,42(12):1308-1313
Single crystals of GdCa4O(BO3)3 (GdCOB) pure and doped with Eu concentration of 1 and 4 at% were grown by the Czochralski and micropulling‐down methods. The distribution of Eu ions in GdCOB crystals was uniform. The substitutions of Eu3+ in Gd, Ca(1) and Ca(2) cation sites and eventually formation Eu2+ have been investigated. The spectroscopic properties of crystals are compared with the properties of nanopowders obtained by sol‐gel method. Radioluminescence spectra of undoped GdCOB crystal show the characteristic emission of Gd3+ at about 312 nm, whereas this emission dramatically decreases in Eu‐doped crystals upon X‐ray excitation, as well as in Eu‐doped nanopowders excited in vacuum ultraviolet (VUV) region. The VUV excitation in the range 125‐333 nm for Eu‐doped samples leads to strong emission in red coming from the 5D0 multiplet of Eu3+, only. In the photoluminescence decay kinetics of 312 nm emissions substantial shortening and departure for single exponential decay in Eu‐doped samples is clearly observed. Higher Eu doping results in further acceleration of the decay. In undoped GdCOB crystal, the lifetime of the Gd3+ 6P7/2 multiplet is 2.79 ms. The Eu3+ 5D0 decay kinetics monitored at 613 nm are rather constant. Numerical fitting of fully exponential curves, reveals lifetimes 2.7 ms for nanopowder and 2.5 ms for single crystal. The results suggest that this material may be used as a red phosphor in plasma display panels in nanopowder form because of strong excitation band of Eu3+ luminescence in the 160‐200 nm regions. Contrary to nanopowder sample, such an excitation band, attributed to the Gd3+–O2– charge transfer was not observed in crystal obtained by the micropulling‐down method. (© 2007 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim) 相似文献