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991.
Covalent organic frameworks (COFs), due to their low-density, high-porosity, and high-stability, have promising applications in gas storage. In this study we have explored the potential of COFs doped with Li and Ca metal atoms for storing hydrogen under ambient thermodynamic conditions. Using density functional theory we have performed detailed calculations of the sites Li and Ca atoms occupy in COF-10 and their interaction with hydrogen molecules. The binding energy of Li atom on COF-10 substrate is found to be about 1.0 eV and each Li atom can adsorb up to three H(2) molecules. However, at high concentration, Li atoms cluster and, consequently, their hydrogen storage capacity is reduced due to steric hindrance between H(2) molecules. On the other hand, due to charge transfer from Li to the substrate, O sites provide additional enhancement for hydrogen adsorption. With increasing concentration of doped metal atoms, the COF-10 substrate provides an additional platform for storing hydrogen. Similar conclusions are reached for Ca doped COF-10. 相似文献
992.
Qian Wu 《Tetrahedron letters》2010,51(37):4806-4807
A simple and five steps total synthesis of Ammosamide B has been developed. The tricyclic pyrroloquinoline in Ammosamides was constructed in one step based on Doebner-Miller reaction between 1,3-diamine-4,6-dinitrobenzene 8 and dimethyl-2-oxo glutaconate 9. 相似文献
993.
T. A. Dang H.‐J. Lunk S. Roychowdhury T. A. Frisk T. J. Bard 《Surface and interface analysis : SIA》2010,42(1):45-51
Solid standards prepared by freeze‐drying consistently showed a high degree of homogeneity. The freezing process, completed in fractions of a second, preserves the original homogeneous distribution of the dopants, and the subsequent sublimation step would minimize any disturbance. Compared to those prepared by conventional methods such as blending and spiking, freeze‐dried standards exhibited superior lateral distribution and better uniform depth distribution. There is, however, a concentration constraint for achieving homogeneity. At 5% doping, segregation was observed in both lateral and depth distribution. Many tungsten standards doped with 10–28 elements ranging from 10 to 200 ppm were successfully prepared and used as controls for a number of analytical techniques including glow discharge mass spectrometry (GDMS) and d.c.‐arc optical emission spectroscopy (OES). Copyright © 2009 John Wiley & Sons, Ltd. 相似文献
994.
Reactions of triguanidinate lanthanide complexes Ln[(iPrN)(NC6H4p-Cl)C(NHiPr)]3 (Ln = Nd, Y) with 3 equiv. of n-BuLi gave [Li(THF)(DME)]3Ln[μ-η2η1 (iPrN)2C(NC6H4p-Cl)]3, which represents the first structurally characterized complexes of lanthanide and lithium metals with dianionic guanidinate ligands. The Nd complex was found to be an effective catalyst for amidation of aldehydes with amines under mild conditions with a wide scope of substrates. 相似文献
995.
Zhongyue Zhou Mingfeng Xie Tang Tang Yijun Zhang Tao Yuan Fei Qi Tom Ni Xueyu Qian 《Plasma Chemistry and Plasma Processing》2010,30(3):391-400
Capacitive radio frequency (RF) discharge of c-C4F8 (octafluorocyclobutane) has been studied with synchrotron vacuum ultraviolet (SVUV) photoionization mass spectrometry (PIMS)
at 4 Torr and 33.33 kHz. Various free radicals and reactive intermediates have been identified through measurement of photoionization
mass spectra and photoionization efficiency (PIE) spectra. CF2=CF2 is main product in the plasma, indicating that the dissociation of c-C4F8 into CF2=CF2 is one of prominent reactions in the present experimental conditions. The observation of large species including C5F8, C5F10 and C6F10 is presented in our work. Besides, the dependences of the signals of neutral species in the discharge of c-C4F8 on RF power are presented in this paper. 相似文献
996.
In this paper, two novel kinds of organic–inorganic monomer, SUA-APEMS and SUA-APS, have been achieved by modifying 5-sulfosalicylic acid (SUA) with 3-aminopropyl-methyl-diethoxylsilane (APEMS) and 3-aminopropyl trimethoxysilane (APS). These two organic–inorganic monomers were used as multi-functional bridged components, which can coordinate to metal ions (Tb3+/Eu3+/Zn2+) with carbonyl groups, strongly absorb ultraviolet and effectively transfer energy to metal ions through their triplet excited state, as well as involve in the sol–gel process with inorganic host precursor tetraethoxysilane (TEOS), resulting two series of molecular hybrid materials (named as SUA-APEMS/APS-RE) with double chemical bond (RE(Zn)–O coordination bond and Si–O covalent bond). The effective intra-molecular energy transfer process gives rise to the characteristic emission of metal ions and the chemical bond make the hybrid materials owning better properties. 相似文献
997.
Miaojing Chen Hong Li Qian Li Zhenghe Xu 《Spectrochimica acta. Part A, Molecular and biomolecular spectroscopy》2010,75(5):1566-1570
The luminescence properties of [Ru(bpy)2MDHIP]2+ (bpy = 2,2′-bipyridine, MDHIP = 2,4-dihydrophenyl-imidazo[4,5-f][1,10]phenanthroline) in the absence and presence of DNA modulated by the introduction of Cu2+ ion and EDTA have been investigated. It is found that the ruthenium(II) complex can insert and stack between the base pairs of calf thymus DNA with MDHIP ligand, and the intramolecular hydrogen bond is located inside of the DNA. The presence of DNA can enhance the luminescence intensities of [Ru(bpy)2MDHIP]2+ both in buffer solution and on an ITO surface. Moreover, the luminescence intensities of [Ru(bpy)2MDHIP]2+ and DNA-bound [Ru(bpy)2MDHIP]2+ are quenched by Cu2+, and next recovered by the addition of EDTA. The repetitive luminescence-modulations have been achieved through the introduction of equimolar Cu2+ and EDTA, respectively. In addition, it becomes evident that the number of luminescence-modulation cycles for [Ru(bpy)2MDHIP]2+ in the absence and presence of DNA is influenced by the cumulative concentrations of CuEDTA, generated successively by the strong coordination of Cu2+ to EDTA. 相似文献
998.
999.
Hu BW Zhao JP Yang Q Zhang XF Evangelisti M Sañudo EC Bu XH 《Dalton transactions (Cambridge, England : 2003)》2010,39(46):11210-11217
Two new azido-Co(II) complexes with pyrazine carboxylato ligands, [Co(N(3))(L)·H(2)O](n) (L = pyrazine-2-carboxylato) (1) and [CoNa(N(3))(2)(L)](n) (2), have been obtained by carefully tuning the Co(II):N(3)(-) ratio. Here we present the structural and magnetic characterization of these new species. Modulation of the coordination environment of Co(II) leads to a variation of the magnetic properties of the obtained compounds. Complex 1 exhibits ferromagnetically coupled [Co(2)] units that form the rungs of the ladder with a nearly negligible coupling between these units, while complex 2 is a 2D arrangement of 1D Co(II) single-chain magnets. 相似文献
1000.
Plate impact experiments on the (210), (100), and (111) planes were performed to examine the role of crystalline anisotropy on the shock-induced decomposition of cyclotrimethylenetrinitramine (RDX) crystals. Time-resolved emission spectroscopy was used to probe the decomposition of single crystals shocked to peak stresses ranging between 7 and 20 GPa. Emission produced by decomposition intermediates was analyzed in terms of induction time to emission, emission intensity, and the emission spectra shapes as a function of stress and time. Utilizing these features, we found that the shock-induced decomposition of RDX crystals exhibits considerable anisotropy. Crystals shocked on the (210) and (100) planes were more sensitive to decomposition than crystals shocked on the (111) plane. The possible sources of the observed anisotropy are discussed with regard to the inelastic deformation mechanisms of shocked RDX. Our results suggest that, despite the anisotropy observed for shock initiation, decomposition pathways for all three orientations are similar. 相似文献