Synthesis and electrochemical properties of nanostructured LiCoO2 fibers as cathode materials for lithium-ion batteries

Nanostructured LiCoO2 fibers were prepared by the sol-gel related electrospinning technique using metal acetate and citric acid as starting materials. The transformation from the xerogel fibers to the LiCoO2 fibers and the nanostructure of LiCoO2 fibers have been investigated in detail. The LiCoO2 fibers with 500 nm to 2 mum in diameter were composed of polycrystalline nanoparticles in sizes of 20-35 nm. Cyclic voltammetry and charge-discharge experiments were applied to characterize the electrochemical properties of the fibers as cathode materials for lithium-ion batteries. The cyclic voltammogram curves indicated faster diffusion and migration of Li+ cations in the nanostructured LiCoO2 fiber electrode. In the first charge-discharge process, the LiCoO2 fibers showed the initial charge and discharge capacities of 216 and 182 (mA.h)/g, respectively. After the 20th cycle, the discharge capacity decreased to 123 (mA.h)/g. The X-ray diffraction and high-resolution transmission electron microscopy analyses indicated that the large loss of capacity of fiber electrode during the charge-discharge process might mainly result from the dissolution of cobalt and lithium cations escaping from LiCoO2 to form the crystalline Li2CO3 and CoF2 impurities.     

Facts and artifacts about aromatic stability estimation

The stability of a set of 105 five-membered π-electron systems (involving aromatic, non-aromatic and anti-aromatic species) was evaluated using six isodesmic reactions of which two belong to the subclass of homodesmotic reactions, which are based on cyclic and acyclic reference systems. We demonstrate that the ‘Resonance Energies’ derived from isodesmotic schemes have obvious flaws and do not correct or cancel other contributions to the energy, such as the changes of hybridization, homoconjugation of heterosubstituted cyclopentadienes, conjugative interactions of CC or CX (X=N or P) with a π or pseudo π orbital at Y (Y=O, S, NH, PH), strain, etc. as effectively as possible. Likewise, ‘aromatic stabilization energies (ASE)’ derived from homodesmotic schemes based on the acyclic reference compounds do not give satisfactory results. We strongly recommend that only cyclic reference compounds should be used for ASE and other aromaticity evaluations. The analysis is based on ab initio optimized geometries at B3LYP/6-311+G^∗∗.     

两性离子流动相测定杂多酸中的磷酸根、氯离子和硫酸根

采用离子色谱法测定杂多酸中痕量阴离子。由于常规的淋洗液(如Na2CO3,NaOH)呈碱性,使杂多酸迅速分解生成磷酸根,致使测定结果偏高。实验通过在常规淋洗液中加入适量两性离子后,调节淋洗液的pH为中性,从而能准确测定杂多酸中磷酸根氯离子和硫酸根的含量值。经过比较分别用去离子水和流动相稀释的样品中磷酸根的测定结果,确定淋洗液的最佳条件为2.5mmol/LNa2CO3-9.0mmol/LCHES,在该条件下测定,快速、准确、灵敏,且有较好的灵敏度和重现性。     

Syntheses,structures and electrochemical properties of ruthenium(II/III) complexes with tetradentate Schiff base ligands

Three unsymmetrical tetradentate Schiff base ligands, H₂salipn, H₂salipn-Br₄ and H₂salipn-Cl₂, have been synthesized from the typical condensation reactions of treating 1,2-diaminopropane with salicylaldehyde, 3,5-dibromosalicylaldehyde and 5-chlorosalicylaldehyde, respectively. Treatment of [RuCl₂(PPh₃)₃] with one equivalent of H₂salipn or H₂salipn-Br₄ in the presence of triethylamine in tetrahydrofuran (THF) afforded the corresponding ruthenium(III) complexes [Ru^IIICl(PPh₃)(salipn)] (1) and [Ru^IIICl(PPh₃)(salipn-Br₄)] (2). Interaction of [RuHCl(CO)(PPh₃)₃] with one equivalent of H₂salipn-Cl₂ or H₂salipn-Br₄ under the same conditions led to isolation of ruthenium(II) complexes [Ru^II(CO)(PPh₃)(salalipn-Cl₂)] (3) and [Ru^II(CO)(PPh₃)(salalipn-Br₄)] (4), respectively, in which one of the imine bonds was nucleophilically attacked by hydride to result in the formation of a mixed imine-amine ligand. The molecular structures of 1?1.5CH₂Cl₂, 2, 3?0.5CH₂Cl₂ and 4 have been determined by single-crystal X-ray crystallography. The electrochemical properties of 1–4 were also investigated. Their cyclic voltammograms displayed quasi-reversible Ru(IV)/Ru(III) and Ru(III)/Ru(II) couples with E^o ranging from 0.67 to 1.05 V and 0.74 to 0.80 V vs. Ag/AgCl (0.1 M), respectively.     

Microwave- and photoirradiation-induced staudinger reactions of cyclic imines and ketenes generated from alpha-diazoketones. A further investigation into the stereochemical process

Reactions of ketenes generated from alpha-diazoketones with a series of acyclic and cyclic imines were investigated under both microwave and photoirradiation conditions. The results indicate that the zwitterionic azabutadiene-type intermediates yielded from imines and ketenes undergo a conrotatory ring closure exclusively to produce beta-lactams. It is notable that no Woodward-Hoffmann product was found under the ultraviolet irradiation. The photoirradiation-induced Staudinger reaction shows a different stereoselectivity from the electrocyclic reaction of substituted 1,3-butadiene.     

电化学免疫分析法研究进展

电化学免疫分析法是将免疫分析与电化学分析技术相结合的一种免疫分析新方法，近十多年来，电化免疫分析的研究有了迅速的发展。本文对电化学的免疫分析法的标记物、免疫方法、电化学检测技术进行了概括总结，并展望了电化学免疫分析的发展前景。     

双马来酰亚胺增韧研究Ⅱ.链扩展双马来酰亚胺及其树脂的合成及表征

合成了一系列结构不同和链长短不一的双马来酰亚胺，并对其结构和性能作了表征，同时研究了它们的固化反应和固化产物的性能。用双马来酰亚胺和二烯丙基化合物反应制造了增韧树脂，研究了该树脂的固化和热稳定性。     

几种杂多阴离子柱撑水滑石的合成与吸附行为

柱撑水滑石类层柱状阴离子粘土是一类新型层柱材料，由于其二维孔道结构的可调变性及潜在的择形催化性能，已引起人们的重视[1-3]．迄今，人们已合成了包括无机和有机阴离子，同多和杂多阴离子（Polyoxometalates，简称POMs）以及配合物阴离子在内的多种柱撑水滑石，其中同多和     

肿瘤患者放疗前后血清八种微量元素含量的研究

对临床、病理、放射线或CT检查确诊的82名癌肿患者，在放疗前后和对42名健康人进行了微量元素铁、锌、铜、锰、硒，铬、钴、镍的分析。研究结果显示：1．癌肿患者血清铜、镍、锰、铬、钴的含量比健康人高，而血清锌、铁、硒的含量却比健康人低；2．血清Cu／Zn、Cr／Zn、Co／Zn、Ni／Zn的比值癌肿患者均比健康人高，而Fe、Zn、Se／Zn的比值却相反。因此，可根据血清铜升高、血清锌降低，血清铜／锌比值升高的特点。用于癌肿的早期诊断；3．癌肿患者放疔后血清铁、锌含量进一步下降，铜、锰、铬的含量也出现降低，唯有硒的含量有所上升。因此，放疗时应注意补充铁、锌、铜元素。