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181.
The anodic reaction of Ni in an alkaline solution was studied by the tip–substrate voltammetry mode of scanning electrochemical microscopy (SECM) and cyclic voltammetry (CV). A platinum microdisc electrode was selected as the tip electrode, which functioned as a pH sensor with transient response capability. The pH value of the solution near the Ni electrode surface varied while the Ni substrate oxidation reaction occurred, and the pH variation could be detected by the tip faradic current. The cyclic voltammogram results showed that two types of hydroxides: i.e. α‐Ni(OH)2 and β‐Ni(OH)2 were formed during Ni oxidation in the lower potential region. In the proceedings of α‐Ni(OH)2 → γ‐NiOOH and β‐Ni(OH)2 → β‐NiOOH, the process of OH? concentration decrease in the solution was ahead and behind of electron transfer in the solid phase, respectively. These results indicate that the OH? adsorption process occurs as an elementary step in the former reaction and the H+ diffusion process from the inner to the outer layer of the solid phase occurs as a subsequent step in the latter reaction. The results also revealed that the oxide film on the Ni surface has a two‐layer structure. The real potential of the oxygen evolution reaction (OER) on the Ni surface with different cycles is also analyzed in the paper. Copyright © 2007 John Wiley & Sons, Ltd. 相似文献
182.
A new method for constructing nonorthogonal localized molecular orbitals (NOLMOs) is presented. The set of highly localized NOLMOs is obtained by minimization of the spread functional starting from an initial set of canonical orthogonal molecular orbitals. To enhance the stability and efficiency, the centroids of the NOLMOs are constrained to be those of the corresponding orthogonal localized molecular orbitals (OLMOs), which are obtained with the Boys criterion in advance. In particular, these centroid constraints make the optimization for each NOLMO independent of the others, which is an attractive feature for application to large systems. The minimization with the constraints incorporated through the multiplier-penalty function method is stable and efficient in convergence. While exhibiting the classical bonding pattern in chemistry and sharing a spatial distribution similar to that of the corresponding OLMOs, the obtained NOLMOs are more compact than the corresponding OLMOs with about 10%-28% reduction in the value of the spread functional and devoid of the troublesome "orthogonalization tails." 相似文献
183.
184.
A highly effective, economical, and environmentally friendly method using of CAN as oxidant and water as solvent for oxidative coupling of N,N-dialkylarylamines was reported. 相似文献
185.
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187.
A Novel Dimeric Coumarin from Clausena lenis 总被引:1,自引:0,他引:1
HongPingHE ShunTingCHEN YueMaoSHEN ChangXiangCHEN YiBinZHAO XiaoJiangHAO 《中国化学快报》2003,14(11):1150-1153
A novel dimeric coumarin (1), a dimeric of seselin named diseselin A, was isolated from the aerial part of Clausena lenis. The structure was elucidated based on the MS, 1D and 2D NMR data. 相似文献
188.
Jiang Ke QIN Xian Zhang BU Yu Fang WANG Zhi Yun DU Xing Yuan WANG Zhi Shu HUANG Lin MA Lin Kun AN Lian Quan GU 《中国化学快报》2005,16(11):1451-1454
The reactions of tanshinone IIA with aromatic aldehydes have been investigated and several 2, T-(substituted arylmethylene) bis (1,6,6-trimethyl-6,7,8,9-tetrahydrophenanthro[1,2-b]- furan- 10, 11-dione) derivatives were obtained, 相似文献
189.
The cyclopeptide, squamtin A (1, formula: C39H60O11N8S), was found to crystallized in two pseudopolymorphisms, i.e. 1·(H2O)3.5 and 1·(H2O)3.9. The composition of the amino acids and their linkage sequences are the same. The main differences between the two kinds of crystals lie in the positions and occupancies of the water molecules, the positions of the sulfur atoms and the conformation of the side chains. The absolute configuration of 1 is established by X-ray analysis in combination with the Marfey's analysis of its hydrolysates. 相似文献
190.
Chen L Jiang F Lin Z Zhou Y Yue C Hong M 《Journal of the American Chemical Society》2005,127(24):8588-8589
A blue luminescent tetradecavanadate compound, [Et4N]5[V14O36Cl], has been synthesized. It possesses an unprecedented half-open basket framework. Through the {ABAB}-type stacking, the {V14O36} clusters form infinite one-dimensional channels with considerable accessible volume in the crystalline state. 相似文献