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991.
Jinzhang Gao Yongjun Liu Wu Yang Lumei Pu Jie Yu Quanfang Lu 《Central European Journal of Chemistry》2005,3(3):377-386
A plasma induced degradation process has been studied to treat 4-nitrotoluene (4-NT) present as an aqueous pollutant. The
plasma was locally generated from a glow discharge around a tip of a platinum anode in an electrolytic solution. The influence
of initial pH and Fe2+ on the degradation was examined. Major intermediates resulting from the degradation process were identified. Amongst the
aromatic intermediates, p-hydroxybenzoic acid was the predominant degradation product. The formation of oxalic acid, malic
acid was also observed. The final products of degradation were NH
4
+
, NO
3
−
and CO2. Based on the analysis of intermediates and the kinetic considerations, the degradation was shown to follow a pseudo-first
order reaction hence, a possible reaction pathway was proposed. 相似文献
992.
Hammed H. A. M. Hassan 《Central European Journal of Chemistry》2005,3(4):803-829
A concise method for a stereocontrolled synthesis of a set of selectively protected disaccharides is reported. Coupling of
the donor 11 onto acceptors 23 and 24, promoted by trimethylsilyl triflate-N-iodosuccinimide (TMSOTf-NIS), generated the disaccharides 25 and 26. Under typical conditions, condensation of the fully protected donor 12 onto acceptors 23 and 24 produced the disaccharides 27 and 28. The building blocks 25–28 were prepared in moderate yields having exclusive β-stereoselectivity. A unique pattern of protecting groups distinguished
clearly between positions to be sulfated and functional groups remaining as free hydroxyl groups. Acetyl and/or levulinoyl
esters temporarily protected the positions to be sulfated, while benzyl ethers were used for permanent protection. The anomeric
positions were protected as allyl ethers, whereas the 4′-positions were masked as p-methoxybenzyl (PMB) ethers. The orthogonality of the PMB and allyl groups can then be used for further elongation of the
chain by recurrent deprotection and activation steps. The hydroxyl group, OH-6, of glucosamine moieties was protected as a
TBDPS ether to avoid oxidation. A five-step deprotection/sulfonation sequence was applied to the disaccharide 27 to generate the corresponding sulfated [β-D-GlcUA-2-OSO3Na-(1→4)-β-D-Glc pNAc]-(1→O-Pro) 34. 相似文献
993.
Shvartsburg AA Tang K Smith RD 《Journal of the American Society for Mass Spectrometry》2005,16(1):2-12
Field asymmetric waveform ion mobility spectrometry (FAIMS) holds significant promise for post-ionization separations in conjunction with mass-spectrometric analyses. However, a limited understanding of fundamentals of FAIMS analyzers has made their design and operation largely an empirical exercise. Recently, we developed an a priori simulation of FAIMS that accounts for both ion diffusion (including anisotropic components) and Coulomb repulsion, and validated it by extensive comparisons with FAIMS/MS data. Here it is corroborated further by FAIMS-only measurements, and applied to explore how key instrumental parameters (analytical gap width and length, waveform frequency and profile, the identity and flow speed of buffer gas) affect FAIMS response. We find that the trade-off between resolution and sensitivity can be managed by varying gap width, RF frequency, and (in certain cases) buffer gas, with equivalent outcome. In particular, the resolving power can be approximately doubled compared to "typical" conditions. Throughput may be increased by either accelerating the gas flow (preferable) or shortening the device, but below certain minimum residence times performance deteriorates. Bisinusoidal and clipped-sinusoidal waveforms have comparable merit, but switching to rectangular waveforms would improve resolution and/or sensitivity. For any waveform profile, the ratio of two between voltages in high and low portions of the cycle produces the best performance. 相似文献
994.
Characterization and electrochemical investigation of boron-doped mesocarbon microbead anode materials for lithium ion batteries 总被引:1,自引:0,他引:1
Mao-Hui Chen Guo-Tao Wu Guang-Ming Zhu Jin-Kua You Zu-Geng Lin 《Journal of Solid State Electrochemistry》2002,6(6):420-427
The structure and anodic performance of boron-doped and undoped mesocarbon microbeads (MCMBs) have been comparatively studied
and the results obtained by XPS, XRD, SEM, Raman spectroscopy and electrochemical measurements are discussed. It is found
that boron doping introduces a depressed d
002 spacing and the larger amount of "unorganized carbon", which induces vacancy formation in the graphite planes and leads to
a quite different morphology from that of the undoped material. Electrochemical charge/discharge cycle tests indicated that
after boron doping the lithium intercalation was carried through at a somewhat higher potential, being attended by greater
irreversible capacity loss.
Electronic Publication 相似文献
995.
侧链液晶聚合物的合成方法,可归纳为3类:一是烯基的单体,如甲基丙烯酸酯,或丙烯酸酯,氯代丙烯酸酯等,经自由基聚合反应,阴离子聚合反应及甲基丙烯酸酯的基团转移聚合反应,得到侧链液晶聚合物;二是变性反应,如聚硅氧烷与丙烯酸酯介 相似文献
996.
Yue Shen Xiaohui Tang Yuwei Xu Haichao Liu Shitong Zhang Bing Yang Yuguang Ma 《中国化学快报》1990,30(11):1947-1950
Cyanophenyl as ancillary acceptor to modify donor-acceptor compound,plays an effective role in shifting the emission color to deep red and maintaining the luminescent efficiency. 相似文献
997.
998.
Molecular structures of three emissive annular digold compounds [Au2(dmpm)(dtc)]Cl (dmpm = Me2PCH2PMe2,dtc = S2CNEt2), 1 , [Au2(dppm)(dtc)]PF6, (dppm = Ph2PCH2PPh2),2,and [Au2(dppe)(dtc)]-(PF2) (dppe = Ph2P(CH2)2PPh2), 3, were determined. All three compounds are dimetallacycles having two gold atoms bridged by a dithiolate ligand and a diphosphine ligand, the geometry around each gold atom being almost linear. All the dimetal lacy die rings are slightly distorted from planarity with intramolecular Au-Au distances shorter than 3.0 Å. Compound 1 forms a polymeric chain through intermolecular Au-Au contacts (3.061 ? 3.135 Å). Compound 2 forms a tetramer through intermolecular Au-Au interactions (Au-Au distances ranging from 3.086 to 3.222 ). Compound 3 is monomeric. All of the compounds luminesce at 77 K in the solid state. Emissions originating from 3LMCT from dtc ligand to Au excited states are assigned. The emission maxima of 1 ? 3 are at 541,535 and 520 nm respectively and are blue shifted as the number of Au-Au interactions is decreased. 相似文献
999.
A biological organism (chitosan) was utilized to preconcentrate lead ions from tap water. This preconcentration was achieved by mixing 0.8 ml of chitosan slurry with 10-50 ml of lead-containing solution and subsequently separating by centrifugation. The chitosan paste was then dissolved in 1 ml of 0.2% nitric acid and analysed by graphite furnace atomic absorption spectrometry. The extraction efficiency can approach 100% in the pH range 4-10. The amount of chitosan used was not critical. The effect of some impurities was also investigated. If six samples were prepared simultaneously, the time needed to preconcentrate each sample was less than 3 min. Two different modes of standard addition (the standard lead solutions being added before and after preconcentration) were used for analysis of tap water samples, and the results obtained by the two modes were found to be quite consistent. 相似文献
1000.
By using laser ablation of the mixtures of a transition metal (M: Ti, Cr, Mn, Fe, Co, Ni, Cu, Zn, Pd, Ag) plus lead, M/Pb binary cluster anions were observed except for Zn, and the number of transition metal atoms contained in the binary clusters is at most 4. This behavior is different from that reported previously for M/Ge binary clusters. The experiments indicate that it is also very difficult to form Al/Pb clusters. The distribution patterns of M/Pb binary alloy cluster anions are remarkably similar to those of pure Pb clusters, consistent with a formation mechanism in which transition metal atoms are sequentially attached to [M(x-1)Pb(y)](-) clusters and thus form [M(x)Pb(y)](-) clusters by a simple condensation process. As the number of transition metal atoms increases, the intensities of binary clusters gradually decrease. It is proposed that [MPb(4)](-) and [MPb(5)](-) cluster anions might be the unit building blocks of M/Pb binary cluster anions, and the layer packing sequences for magic clusters are predicted on this basis. The [M(x)Pb(y)](-) binary clusters containing 13 atoms (x + y = 13; x not equal 0) are proposed to have an icosahedral structure. 相似文献