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121.
Monodisperse and core-shell-structured SiO2@YBO3:Eu3+ spherical particles: synthesis and characterization 总被引:1,自引:0,他引:1
Y0.9Eu0.1BO3 phosphor layers were deposited on monodisperse SiO2 particles of different sizes (300, 570, 900, and 1200 nm) via a sol-gel process, resulting in the formation of core-shell-structured SiO2@Y0.9Eu0.1BO3 particles. X-ray diffraction (XRD), field emission scanning electron microscopy (FE-SEM), transmission electron microscopy (TEM), photoluminescence (PL), and cathodoluminescence (CL) spectra as well as lifetimes were employed to characterize the resulting composite particles. The results of XRD, FE-SEM, and TEM indicate that the 800 degrees C annealed sample consists of crystalline YBO3 shells and amorphous SiO2 cores, in spherical shape with a narrow size distribution. Under UV (240 nm) and VUV (172 nm) light or electron beam (1-6 kV) excitation, these particles show the characteristic 5D0-7F1-4 orange-red emission lines of Eu3+ with a quantum yield ranging from 36% (one-layer Y0.9Eu0.1BO3 on SiO2) to 54% (four-layer Y0.9Eu0.1BO3 on SiO2). The luminescence properties (emission intensity and color coordinates) of Eu3+ ions in the core-shell particles can be tuned by the coating number of Y0.9Eu0.1BO3 layers and SiO2 core particle size to some extent, pointing out the great potential for these particles applied in displaying and lightening fields. 相似文献
122.
Billion‐Fold Enhancement in Sensitivity of Nuclear Magnetic Resonance Spectroscopy for Magnesium Ions in Solution 下载免费PDF全文
Dr. Alexander Gottberg Dr. Monika Stachura Dr. Magdalena Kowalska Dr. Mark L. Bissell Dr. Vaida Arcisauskaite Prof. Klaus Blaum Alexander Helmke Dr. Karl Johnston Dr. Kim Kreim Prof. Flemming H. Larsen Prof. Rainer Neugart Prof. Gerda Neyens Ronald F. Garcia Ruiz Daniel Szunyogh Prof. Peter W. Thulstrup Dr. Deyan T. Yordanov Prof. Lars Hemmingsen 《Chemphyschem》2014,15(18):3929-3932
β‐nuclear magnetic resonance (NMR) spectroscopy is highly sensitive compared to conventional NMR spectroscopy, and may be applied for several elements across the periodic table. β‐NMR has previously been successfully applied in the fields of nuclear and solid‐state physics. In this work, β‐NMR is applied, for the first time, to record an NMR spectrum for a species in solution. 31Mg β‐NMR spectra are measured for as few as 107 magnesium ions in ionic liquid (EMIM‐Ac) within minutes, as a prototypical test case. Resonances are observed at 3882.9 and 3887.2 kHz in an external field of 0.3 T. The key achievement of the current work is to demonstrate that β‐NMR is applicable for the analysis of species in solution, and thus represents a novel spectroscopic technique for use in general chemistry and potentially in biochemistry. 相似文献
123.
Liu L Wu D Li X Wang S Li H Li J Wang W 《Chemical communications (Cambridge, England)》2012,48(11):1692-1694
An enantioselective Michael addition of ketones to alkylidenemalononitriles catalyzed by chiral primary amine I with (R)-5c as a co-catalyst in good yields (>90%) and with good enantioselectivities (85-96% ee) has been developed. The strategy has also been extended to a three-component version through a domino Knoevenagel/Michael sequence with similar or better outcomes. 相似文献