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121.
环戊二烯基希土氯化物是一类合成希土有机配合物的重要前身。尽管在1980年前没能成功地合成含轻希土元素的这类配合物,但目前已发现,采用具有较大体积的取代环戊二烯做配体,如C_5Me_5H,C_5H_3〔Si(CH_3)_3〕_2H,C_5Me_4C_3H_7H和桥联的配体(C_5H_4)_2(CH_2)_3H_2都可得到相应的取代环戊二烯基轻希土氯化物。控制LnCl_3和CpNa的反应摩尔比也可以成功地得到这类轻希土的环戊二烯基氯化物。 相似文献
122.
采用穆斯堡尔谱及X光衍射法研究了共沉淀法制备的不同Fe/Mn比催化剂在焙烧、合成气还原及FT反应后体系相结构的变化。结果表明:锰助剂的加入使催化本相由铁磁性逐渐转化为超顺磁性,相应使催化剂还原逐渐难,Mn助剂促进了FT合成反应进行。反应性能与Fe/Mn尖晶石(Fe1-yMny)3O4组成含量及式中y大小密切相关,与MnCo3及MnO的存在也有一定关系。富铁催化剂中Mn主要起电子助剂作用,而富锰催化 相似文献
123.
Growth of porous single-crystal Cr2O3 in a 3-D mesopore system 总被引:1,自引:0,他引:1
Jiao K Zhang B Yue B Ren Y Liu S Yan S Dickinson C Zhou W He H 《Chemical communications (Cambridge, England)》2005,(45):5618-5620
Single-crystal Cr2O3 with regular mesopores has been synthesized using mesoporous silica KIT-6 as a template and characterized by using XRD, HRTEM and nitrogen adsorption/desorption. 相似文献
124.
125.
Zhang WW Ren XM Li H Xie JL Lu CS Zou Y Ni ZP Meng QJ 《Journal of colloid and interface science》2003,268(1):173-180
Self-assembled monolayers (SAMs) of functionalized azobenzene thiols (RAzoCnSH, n=3-6 for R=H, abbreviated as AzoCnSH; and n=4 for R=CH(3)CONH, abbreviated as aaAzoC4SH) on different substrates RAzoCnSz.sbnd;z.sfnc;S (S represents substrates of vacuum-deposited gold (Au), silver foil (Ag), HNO(3) etched silver foil (EAg), and silver mirror (mAg)) have been studied by SERS in the near-infrared region. SERS of the SAMs on EAg and/or mAg exhibit SERS effects that vary with etching time and/or deposition time. The most appropriate time is 5 s for etching in 1:1 HNO(3) and 40 s for deposition in 0.1 M Ag(NH(3))(2)NO(3). Further, a layer of Ag mirror was conveniently deposited on the top of the SAMs on different substrates, yielding a more efficient SERS-active system possessing a "sandwiched" structure of mAgz.sfnc;RAzoCnS-z.sfnc;S. An appropriate surface roughness is required for the strongest SERS effect. Scanning electron microscopy (SEM) indicates that there exist a large number of projects around 100 nm on the surface showing the strongest SERS effect. When the surface roughness is decreased or increased, the SERS effect decreases sharply. The relationship between the SERS effect and the structural nature was investigated and showed that the enhancement factor decays exponentially with increasing in distances of the azobenzene group from the underlying substrate or the overlying silver mirror. This result reveals that the SERS effect may be the result of the electromagnetic coupling effect between two metal layers. 相似文献
126.
Xing Yong Wang Jing Nan Cui Wei Min Ren Feng Li Chun Liang Lu Xu Hong Qian State Key Laboratory of Fine Chemicals Dalian University of Technology Dalian China School of Chemical Engineering Technology China University of Mining & Technology Xuzhou China Shanghai Key Laboratory of Chemical Biology East China University of Science Technology Shanghai China 《中国化学快报》2007,18(6):681-684
Baker's yeast mediated reduction of acenaphthenequinone within 4-10 h afforded mono-hydroxyacenaphthenone mainly with low enantioselectivity, the substrate and mono-hydroxyacenaphthenone product almost converted to dihydroxyacenaphthene after 48 h. By control of the reaction time and in the presence of DMF as co-solvent, the reduction of 6-substituted acenaphthenequinones under vigorous agitation afforded the corresponding 2-hydroxyacenaphthenones in 24-84% yields with 10-93% ee. 相似文献
127.
Three ion-pair complexes, [RbzPy](+)[Ni(mnt)(2)](-) (mnt(2)(-) = maleonitriledithiolate; [RbzPy](+) = 4-R-benzylpyridinium; R = Br (1), Cl (2), and NO(2) (3)), with unusual magnetic properties have been synthesized and characterized. The crystal structures of 1 and 2 have been solved. The two complexes belong to the P2(1)/c space group with Z = 4 and C(20)H(11)BrN(5)NiS(4), a = 12.0744(17) A, b = 26.369(4) A, c = 7.440(3) A, and beta = 102.63(3) degrees for 1 and C(20)H(11)ClN(5)NiS(4), a = 12.105(2) A, b = 26.218(4) A, c = 7.374(2) A, and beta = 102.55(2) degrees for 2, respectively. The [Ni(mnt)(2)](-) anions in 1-3 form uniformly spaced one-dimensional (1-D) magnetic chains of s = 1/2 at room temperature. The temperature dependences of the susceptibility for 1-3 show that they undergo phase transitions. All three complexes are paramagnetic in their high-temperature (abbreviation HT) phase and diamagnetic in the low-temperature (abbreviation LT) phase because of strong dimerization along the stacking direction. The results of thermal analysis (DSC) further confirm that the phase transition for 1 and 2 is first-order but maybe second-order for 3. The phenomena observed in this study are similar to those of the 1-D radical systems. 相似文献
128.
Core-shell colloidal particles were prepared with the core of monodisperse melamine formaldehyde particles (MF) with a diameter of 3.5 μm. The shell deposited on the core by the layer-by-layer (LbL) self-assembly was made with a copolymer ANp3 of 2-acrylamido-2-methylpropanesulfonate sodium (AMPS) and 3 mol% naphthalene label monomer and poly(diallyldimethylammonium chloride) (PD). Nonradiative energy transfer (NRET) from the naphthalene labels deposited on the MF particles to pyrene labels at a polyelectrolyte APy3, a copolymer of AMPS and 3 mol% pyrene label monomer, or to an ionic pyrene probe 1-pyrenemethylamine hydrochloride (PyMeA · HCl) in water was observed. The NRET efficiency was expressed as the emission intensity ratio I/I0 of naphthalene with and without existence of pyrene in the surrounding solution. With increasing pyrene concentration, I/I0 decreased down to about 0.2 and the mechanism for this NRET from the inner naphthalene label to the pyrene labels in solution is still ambiguous. 相似文献
129.
XI Jingyu QIU Xinping ZHU Wentao & CHEN Liquan Department of Chemistry Tsinghua University Beijing China 《中国科学B辑(英文版)》2005,48(6)
All solid-state lithium polymer batteries may be one of the best choices for the future electrochemical power source, characterized by high energy densities, good cyclability, reliability and safety[1,2]. Owing to its potential capability to replace the t… 相似文献
130.
The infrared emission of CO trapped in solid Ne and Ar is observed at low temperature. The first vibrational level of 12C16O is excited by a Q-switched frequency doubled CO2 laser. The emission spectrum consists of several lines arising from upper vibrational levels of 12C16O and also of 13C16O and 12C18O which are present in natural abundance. An interpretation is proposed which is based on the assumption that long range dipole—dipole interaction is the main physical process involved in these experiments. Resonance energy transfer produces an energy migration among 12C16O molecules without any change in vibrational populations. Phonon assisted energy transfer takes place between vibrational levels of the various isotopic species present in the solution. In order to satisfy the resonance condition a phonon is emitted or absorbed whose energy compensates for the energy mismatch between the transitions in each interacting molecule due to isotopic effect and or vibrational anharmonicity. The range of this process is greatly extended by energy migration. At the low phonon bath temperature phonon emission is much more probable than phonon absorption. So a strong excitation of upper vibrational levels with in some cases population inversions is observed.Molecular impurities act as efficient quenching centers even at very low concentration. When highly purified samples are used, the fluorescence decay time is found to be 20.6 ms in Ne and 14.5 ms in Ar and does not significantly depend upon concentration and temperature. It is concluded that radiationless relaxation is unimportant. 相似文献