Li_3PO_4包覆LiMn_2O_4正极材料的结构表征和电化学性能

采用共沉淀法在尖晶石LiMn2O4颗粒表面包覆Li3PO4.XRD、SEM研究结果表明,包覆后的材料仍为尖晶石结构,粒径均匀.电化学性能测试表明,Li3PO4包覆层的存在,减少了正极材料与电解液的直接接触,抑制了高温下电解液对LiMn2O4材料的侵蚀,从而有效改善了高温下材料的循环性能.在40℃时,包覆样品的比容量衰减率都低于未包覆样品,其中包覆1%Li3PO4的样品的初始比容量为110.4mAh/g,50次循环后比容量为84.1mAh/g.     

Inhibitory study of some novel Schiff base derivatives on Staphylococcus aureus by microcalorimetry

The effect of a series of novel Schiff base compounds on Staphylococcus aureus was studied by microcalorimetric method at 37 °C The results showed that all of the organic compounds had the capacity to inhibit the growth of S. aureus in different extent. And the extent and duration of the inhibitory effect on the growth of S. aureus, judged from the rate constant (k), varied with the different structure of the Schiff base compounds. According to the power-time curves, the multiplication rate constant and inhibition ratio were calculated. The growth rate constant of S. aureus (in log phase) in the presence of Schiff base compounds decreased with the increasing of the concentrations of these compounds regularly. The experimental results revealed that the hydrophilicity of Schiff bases had a great influence on their antibacterial activity. Of these Schiff bases, the greater their hydrophilicity, the higher their antibacterial activity. The antibacterial structure-activity relationship (SAR) of Schiff base derivatives was also briefly discussed.     

手性3,5-二甲基-2-芳基-2-吗啉醇盐酸盐的合成及其晶体结构

以(S)-2-氨基丙醇为手性源与α-溴-3-氯苯丙酮反应, (R)-2-氨基丙醇为手性源与6-甲氧基-2-(2-溴丙酰基)萘反应, 分别合成了手性纯化合物(2R,3R,5S)-3,5-二甲基-2-(3-氯苯基)-2-吗啉醇盐酸盐(4a)和(2S,3S,5R)-3,5-二甲基-2-(6-甲氧基-2-萘基)-2-吗啉醇盐酸盐(4b), 利用X射线单晶衍射仪测定了两化合物的晶体结构和两化合物的空间结构, 并初步分析两化合物空间结构, 化合物4a晶体属正交晶系, 空间群为P2₁2₁2, 晶胞参数为: a＝0.8718(2) nm, b＝0.7883(2) nm, c＝2.0247(6) nm, Z＝4, V＝1.3915(7) nm³, D_c＝1.328 g/cm³, F(000)＝584, R₁＝0.0399, wR₂＝0.0797, S＝1.042. 化合物4b晶体属正交晶系, 空间群为P2₁2₁2₁, 晶胞参数为: a＝0.71035 (9) nm, b＝0.77703(10) nm, c＝2.9820(4) nm, Z＝4, V＝1.6318(4) nm³, D_c＝1.318 g/cm³, F(000)＝688, R₁＝0.0520, wR₂＝0.1108, S＝0.994.     

Recycling Chiral Organocatalyst （4S）-Phenoxy-（S）-proline for Direct Asymmetric Aldol Reaction in Ionic Liquid （bmim）PF6

Room temperature ionic liquid (bmim)PF6 was evaluated for recycling an organocatalyst (4S)-phenoxy-(S)-proline for direct asymmetric aldol reactions. The desired aldol products were obtained with good yields up to 93.2% and enantioselectivities up to 88.5%, and isolation of the products by simple extraction allowed recycling the ionic liquid containing the immobilized catalyst in subsequent reactions without significant decrease of yields and enantioselectivities.     

(π)C—H···S, (allyl)C—H···C(π) and π···π intermolecular interactions: synthesis, characterization, and crystal structure of 2,2′-bipyridine bis(diallyldithiocarbamato)zinc(II)

A mixed-ligand Zn(II) complex formulated as [Zn(aldtc)₂(bipy)] (aldtc=diallyldithiocarbamate; bipy=2,2′-bipyridine) was synthesized and characterized by IR, ¹H and ¹³C NMR spectral measurements and X-ray crystallography. The crystal structure of this complex indicates that Zn has a distorted octahedral geometry. The Zn—N distances are invariant (2.168(2) Å), while those of the Zn—S are slightly different (2.5408(9) and 2.5440(9) Å). The N—Zn—N, S—Zn—S and N—Zn—S bond angles are in the range 75.35(13)–99.75(7)°, 70.48(3)–161.02(5)° and 95.26(7)–160.32(7)°, respectively. The crystal packing of the complex shows different motifs of supramolecularity resulting from both hydrophilic ((π)C—H···S) and hydrophobic ((allyl)C—H···C(π)) intermolecular interactions. These interactions result in a chain arrangement of molecules along crystallographic c axis and the chains are further connected via π···π stacking along with ((π)C—H···S along b axis leading to an overall crystal packing that can be regarded as layers of complexes along bc plane, which are held together through nonconventional hydrogen bonding and π···π stacking.     

The structure of cyclopentene oxide determined by gas phase electron diffraction

The r_g structure of cyclopentene oxide has been determined by the simultaneous least squares analysis of electron diffraction and microwave spectroscopic data. The investigation has reaffirmed previous studies indicating that the molecule prefers a boat conformation. The methylene and epoxide flap angles obtained are 152.3±2.1° and 104.7±1.0° respectively. Other structural parameters determined are: r_g (C-H avg.) = 1.120±0.004 Å; r_g (C-C avg.) = 1.538±0.002 Å; r_g (C-O) = 1.443±0.003 Å, and r_g (C-C) = 1.482±0.004 Å for the carbon-carbon bond in the three membered epoxide ring. These results compare favorably with the reported structures of ethylene oxide and cyclohexene oxide. A tentative rationalization of the unusual boat conformation is also offered.     

微波辅助快速制备2D/1D ZnIn2S4/TiO2 S型异质结及其光催化制氢性能

The threat and global concern of energy crises have significantly increased over the last two decades. Because solar light and water are abundant on earth, photocatalytic hydrogen evolution through water splitting has been considered as a promising route to produce green energy. Therefore, semiconductor photocatalysts play a key role in transforming sunlight and water to hydrogen energy. To date, various photocatalysts have been studied. Among them, TiO₂ has been extensively investigated because of its non-toxicity, high chemical stability, controllable morphology, and high photocatalytic activity. In particular, 1D TiO₂ nanofibers (NFs) have attracted increasing attention as effective photocatalysts because of their unique 1D electron transfer pathway, high adsorption capacity, and high photoinduced electron–hole pair transfer capability. However, TiO₂ NFs are considered as an inefficient photocatalyst for the hydrogen evolution reaction (HER) because of their disadvantages such as a large band gap (~3.2 eV) and fast recombination of photoinduced electron–hole pairs. Therefore, the development of a high-performance TiO₂ NF photocatalyst is required for efficient solar light conversion. In recent years, several strategies have been explored to improve the photocatalytic activity of TiO₂ NFs, including coupling with narrow-bandgap semiconductors (such as ZnIn₂S₄). Recently, microwave (MW)-assisted synthesis has been considered as an important strategy for the preparation of photocatalyst semiconductors because of its low cost, environment-friendliness, simplicity, and high reaction rate. Herein, to overcome the above-mentioned limiting properties of TiO₂ NFs, we report a 2D/1D ZnIn₂S₄/TiO₂ S-scheme heterojunction synthesized through a microwave (MW)-assisted process. Herein, the 2D/1D ZnIn₂S₄/TiO₂ S-scheme heterojunction was constructed rapidly by using in situ 2D ZnIn₂S₄nanosheets decorated on 1D TiO₂ NFs. The loading of ZnIn₂S₄ nanoplates on the TiO₂ NFs could be easily controlled by adjusting the molar ratios of ZnIn₂S₄ precursors to TiO₂ NFs. The photocatalytic activity of the as-prepared samples for water splitting under simulated solar light irradiation was assessed. The experimental results showed that the photocatalytic performance of the ZnIn₂S₄/TiO₂ composites was significantly improved, and the obtained ZnIn₂S₄/TiO₂ composites showed increased optical absorption. Under optimal conditions, the highest HER rate of the ZT-0.5 (molar ratio of ZnIn₂S₄/TiO₂= 0.5) sample was 8774 μmol·g^-1·h^-1, which is considerably higher than those of pure TiO₂ NFs (3312 μmol·g^-1·h^-1) and ZnIn₂S₄nanoplates (3114 μmol·g^-1·h^-1) by factors of 2.7 and 2.8, respectively. Based on the experimental data and Mott-Schottky analysis, a possible mechanism for the formation of the S-scheme heterojunction between ZnIn₂S₄ and TiO₂ was proposed to interpret the enhanced HER activity of the ZnIn₂S₄/TiO₂heterojunctionphotocatalysts.      

Redox behavior of V/MgO catalyst in H2S wet oxidation at room temperature

The room temperature wet catalytic oxidation was conducted in a batch reactor with V/MgO catalyst. The XRD study of the catalyst used indicated that V/MgO could not only oxidize H2S to sulfur selectively, but also prevent the sulfidation of metal oxide effectively at the room temperature. The XPS study indicated that the H2S oxidation with V/MgO could proceed by a redox mechanism (V⁵⁺↔ V⁴⁺) and that V³⁺ formation (V⁴⁺→ V³⁺), was responsible for the deactivation of V/MgO. This revised version was published online in June 2006 with corrections to the Cover Date.     

Thin-layer chromatographic separation of serotonin from epinephrine and norepinephrine

A thin-layer chromatographic procedure is reported for the separation of serotonin from epinephrine and norepinephrine. The method involves the use of ethylenediaminetetraacetic acid-impregnated silica gel G plates and n-butanol-ethanol-acetic acid-water (8:2:1:3) as developer. Serotonin is well separated from both epinephrine and norepinephrine. Epinephrine and norepinephrine overlapped slightly but were both detectable. The procedure is thus applicable to the separation of all three biogenic amines in spite of the absence of an absolutely clear separation of epinephrine from norepinephrine.     

A theoretical study of electronic excited states of photosynthetic reaction center in Rhodopseudomonas viridis

The electronic singlet vertical excited states of photosynthetic reaction center (PSRC) in Rhodopseudomonas (Rps.) viridis were investigated by ZINDO and INDO/S methods. The effects of the interactions of pigment-pigment and pigment-protein on the electronic excitations were examined. The calculation results showed that the interactions of pigment-pigment and pigment-protein play an important role in reasonably assigning the experimental absorption and circular dichroism (CD) spectra of PSRC in Rps. virids. By comparing the theoretically computed excited states with the experimental absorption and CD spectra, satisfactory assignments of the experimental spectroscopic peaks were achieved.