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951.
100公里以上的大气分子离子主要为NO~+。它的辐射特点及它与电子、原子或分子的相互作用,对于理解大气的化学过程具有特别重要的意义。为了研究这些过程,确定NO~+分子离子基态及其各个激发态的分子势能函数是非常重要的。精确的X~1Σ~+,A~1Ⅱ和a~3∑~+势能曲线已发表;基于光电子谱的研究发现了NO~+的其它激发态,但对于这些激发态的研究尤其是势能函数的研究不多。本文研究并导出NO~+的基态和10个激发态的势能函数。 相似文献
952.
953.
富氧条件下乙炔选择催化还原NOx 总被引:1,自引:0,他引:1
Acetylene as a reducing agent of metal exchanged HY catalysts, for selective catalytic reduction of NO in the reaction system of 0.16% NO, 0 (C2H2-SCR) was investigated over a series 08% C2H2, and 9.95% O2 (volume percent) in He. 75% of NO conversion to N2 with hydrocarbon efficiency about 1.5 was achieved over a Ce-HY catalyst around 300 ℃. The NO removal level was comparable with that of selective catalytic reduction of NOx by C3H6 reported in literatures, although only one third of the reducing agent in carbon moles was used in the C2H2-SCR of NO. The protons in zeolite were crucial to the C2H2-SCR of NO, and the performance of HY in the reaction was significantly promoted by cerium incorporation into the zeolite. NO2 was proposed to be the intermediate of NO reduction to N2, and the oxidation of NO to NO2 was rate-determining step of the C2H2-SCR of NO over Ce-HY. The suggestion was well supported by the results of the NO oxidation with O2, and the C2H2 consumption under the conditions in the presence or absence of NO. 相似文献
954.
In this work, the gold nanoparticle self-assembly behavior of mica-surface-confined polyelectrolyte/surfactant complex films was investigated. First, modified partially hydrated polyacrylamide (MHPAM)/hexadecyltrimethylammonium bromide (CTAB) complex films were deposited on the mica surface using Langmuir–Blodgett technique. Then, the preadsorbed MHPAM/CTAB complex film mica plate was dipped into the gold aqueous solution and the interesting fractal nanostructured gold network was formed. In addition, the effect of dipping time on gold nanoparticle self-assembly morphology was studied. The mechanism of formation process is briefly proposed. 相似文献
955.
Three new stephaoxocane‐type alkaloids, stephalonganines A–C ( 1 – 3 ), together with the known eletefine ( 4 ), were isolated from the whole plant of Stephania longa. Their structures were fully characterized spectroscopically, and the absolute configurations of the new alkaloids were assigned by comparison of their circular‐dichroism (CD) data with those of 1,2‐dihydrostephaoxocanine ( 5 ), in combination with 2D‐NMR experiments. 相似文献
956.
[structure: see text]. A new series of dendritic two-photon absorbing chromophores containing triphenylamine moiety as a core or branching points have been synthesized through a convergent synthetic strategy. One-photon and two-photon optical properties of these molecules were characterized. In the nanosecond time domain, these molecules exhibited large two-photon absorption (TPA) cross sections up to 7.56-12.2 x 10(-44) s cm(4) at 800 nm, indicating that these molecular structures were viable candidates for various two-photon related applications. 相似文献
957.
Xuchu Ma Xuebing Li Yi Du Fen Xu Yitai Qian 《Journal of solid state chemistry》2004,177(10):3824-3829
The micro-sized Sb2O3 octahedra can be synthesized on a large scale via a simple PEG-1000 polymer-assisted hydrothermal route (PAHR) in the temperature range of 160-180 °C for 10-14 h. The structures, compositions, and morphologies of the as-synthesized products are derived from X-ray power diffraction pattern, X-ray photoelectron spectra, and field emission scanning electronic microscope. Meanwhile, the optical properties of the micro-sized Sb2O3 octahedra are studied by their photoluminescene spectroscopy and Raman spectrum. Furthermore, the possible growth mechanism of the micro-metered Sb2O3 octahedra is discussed on the basis of a series of supplementary experiments. And it has been found that PEG-1000, sodium tartrate, the reaction temperature, and the reaction time have considerable effects on the final morphology of Sb2O3, while the pH value has an influence on the formation of the Sb2O3 crystals. 相似文献
958.
考察了反应温度、气体空速和进料中CH4:O2比值对Mo2C/Al2O3催化的POM反应制合成气的影响.结果发现较高的温度具有较高的甲烷转化率、CO和H2的选择性;而在较低的温度下,对CO的选择性比对H2的影响更大.反应气体的空速较小时对于甲烷的转化率、CO和H2的选择性是有利的;而在较高的气体空速下,氢气的选择性则更低.进料中CH4:O2比值稍高于2:1时有利于获得高的甲烷转化率、CO和H2的选择性.并且还可以增加催化剂的稳定性.当CH4:O2比值低于2:1时.甲烷转化率、CO和H2选择性随反应的进行急剧下降.而当此比值调整到高于2:1时.转化率和选择件都可以得到恢复。 相似文献
959.
Systematic synthesis and characterization of single-crystal lanthanide orthophosphate nanowires 总被引:8,自引:0,他引:8
Fang YP Xu AW Song RQ Zhang HX You LP Yu JC Liu HQ 《Journal of the American Chemical Society》2003,125(51):16025-16034
A simple hydrothermal method has been developed for the systematic synthesis of lanthanide orthophosphate crystals with different crystalline phases and morphologies. It has been shown that pure LnPO(4) compounds change structure with decreasing Ln ionic radius: i.e., the orthophosphates from Ho to Lu as well as Y exist only in the tetragonal zircon (xenotime) structure, while the orthophosphates from La to Dy exist in the hexagonal structure under hydrothermal treatment. The obtained hexagonal structured lanthanide orthophosphate LnPO(4) (Ln = La, Ce, Pr, Nd, Sm, Eu, Gd, Tb, and Dy) products have a wirelike morphology. In contrast, tetragonal LnPO(4) (Ln = Ho, Er, Tm, Yb, Lu, Y) samples prepared under the same experimental conditions consist of nanoparticles. The obtained hexagonal LnPO(4) (Ln = La --> Tb) can convert to the monoclinic monazite structured products, and their morphologies remained the same after calcination at 900 degrees C in air (Hexagonal DyPO(4) is an exceptional case, it transformed to tetragonal DyPO(4) by calcination), while the tetragonal structure for (Ho--> Lu, Y)PO(4) remains unchanged by calcination. The resulting LnPO(4) (Ln = La --> Dy) products consist almost entirely of nanowires/nanorods with diameters of 5-120 nm and lengths ranging from several hundreds of nanometers to several micrometers. Europium doped LaPO(4) nanowires were also prepared, and their photoluminescent properties were reported. The optical absorption spectrum of CePO(4) nanowires was measured and showed some differences from that of bulk CePO(4) materials. The possible growth mechanism of lanthanide phosphate nanowires was explored in detail. X-ray diffraction, field-emission scanning electron microscopy, transmission electron microscopy, electron diffraction, infrared absorption spectra, X-ray photoelectron spectroscopy, optical absorption spectra, and photoluminescence spectra have been employed to characterize these materials. 相似文献
960.
Jian Yang Vernica Postils Michael I. Lipschutz Meg Fasulo Christophe Raynaud Eric Clot Odile Eisenstein T. Don Tilley 《Chemical science》2020,11(19):5043
A cationic nickel complex of the bis(8-quinolyl)(3,5-di-tert-butylphenoxy)phosphine (NPN) ligand, [(NPN)NiCl]+, is a precursor to efficient catalysts for the hydrosilation of alkenes with a variety of hydrosilanes under mild conditions and low catalyst loadings. DFT studies reveal the presence of two coupled catalytic cycles based on [(NPN)NiH]+ and [(NPN)NiSiR3]+ active species, with the latter being more efficient for producing the product. The preferred silyl-based catalysis is not due to a more facile insertion of alkene into the Ni–Si (vs. Ni–H) bond, but by consistent and efficient conversions of the hydride to the silyl complex.A cationic nickel complex of the bis(8-quinolyl)(3,5-di-tert-butylphenoxy)phosphine (NPN) ligand, [(NPN)NiCl]+, is a precursor to efficient catalysts for the hydrosilation of alkenes with hydrosilanes under mild conditions and low catalyst loadings. 相似文献