Diastereoselective diaza-Cope rearrangement reaction

Steric effect is used to obtain a highly diastereoselective rearrangement reaction.     

Electrochemical performance of graphene nanosheets as anode material for lithium-ion batteries

Graphene nanosheets (GNSs) were prepared from artificial graphite by oxidation, rapid expansion and ultrasonic treatment. The morphology, structure and electrochemical performance of GNSs as anode material for lithium-ion batteries were systematically investigated by high-resolution transmission electron microscope, scanning electron microscope, X-ray diffraction, Fourier transform infrared spectroscopy and a variety of electrochemical testing techniques. It was found that GNSs exhibited a relatively high reversible capacity of 672 mA h/g and fine cycle performance. The exchange current density of GNSs increased with the growth of cycle numbers exhibiting the peculiar electrochemical performance.     

Composite thin film by hydrogen-bonding assembly of polymer brush and poly(vinylpyrrolidone)

Based on hydrogen-bonding layer-by-layer (LBL) assembly in aqueous solution, poly(vinylpyrrolidone) (PVPON) and a spherical polymer brush with a poly(methylsilsesquioxane) (PSQ) core and poly(acrylic acid) (PAA) hair chains were used to fabricate composite multilayer thin films. Hydrogen bonding as the driving force was confirmed by FT-IR spectrometry. A simple method (Filmetric F20) was introduced to determine the thickness and refractive index of the films. The film thickness was found to be a linear function of the number of bilayers. The average increase in thickness per bilayer is 28.3 nm. The film morphology was characterized with scanning electron microscopy and atomic force microscopy. The images obtained from the two instruments show a great resemblance. The films were further calcined to get an inorganic film by removing the organic components, or treated with tetrabutylammonium fluoride (TBAF) to remove the PSQ core and get an organic film. The optical properties and morphological changes induced by these treatments were also studied.     

Flame retardancy and thermal degradation of intumescent flame retardant polypropylene with MP/TPMP

The performances of the novel intumescent flame retardant (IFR) polypropylene (PP) composites containing melamine phosphate (MP) and tris(1‐oxo‐2,6,7‐trioxa‐1‐phosphabicyclo[2,2,2]methylene‐4)phosphate (TPMP) were investigated. The flame retardancy of IFR‐PP system was characterized by limiting oxygen index (LOI) and UL 94 and cone calorimeter. The morphology of the char obtained after cone calorimeter testing was studied by scanning electron microscopy (SEM). The thermal oxidative degradation (TOD) of the composites was investigated by using thermogravimetric analysis (TGA) and real‐time Fourier transform infrared spectroscopy (RT‐FTIR). Compared with the PP/ TPMP or PP/ MP binary composite, at the same addition level, the LOI values of the PP/MP/TPMP ternary composites increase and reach V‐0 at the suitable MP/TPMP ratio. The results of TGA and RT‐FTIR showed the existence of the interaction between IFR and PP. Copyright © 2008 John Wiley & Sons, Ltd.     

A Novel μ2‐(H2O)‐Bridged Double‐Chain Coordination Polymer [Cd(pc)(phen)(H2O)]n with Rhombic Grids (H2pc = pamoic acid,phen = 1,10‐phenanthroline)

A novel coordination polymer [Cd(pc)(phen)(H₂O)]_n (H₂pc = pamoic acid, phen = 1,10‐phenanthroline) has been synthesized under hydrothermal conditions. Single crystal X‐ray diffraction analysis reveals that the compound crystallizes in triclinic space group P1. All the Cd^II atoms in the compound are hexacoordinate and are linked by pamoicate ligands to form a one‐dimensional zigzag chain. Furthermore, two adjacent zigzag chains are connected by the μ₂‐(H₂O) molecules to form a double‐chain with rhombic grids. There exist intermolecular C–H ··· π contacts, π–π stacking and hydrogen‐bonding interactions. Compound 1 displays strong fluorescent emission in the solid state at room temperature.     

正交相MoO3的制备、表征及其电化学嵌锂性质

用化学沉淀-水热法在较低的温度下制备了片状正交相MoO3,由XRD、FT-IR、XPS和SEM表征了产物的相态、结构、成分和形貌。电化学测试表明,在0.1mA.cm-2的电流密度和1.2~3.5V电压范围,其初始放电容量为663mA.h.g-1,有望成为理想的锂离子插层材料。     

Preparative isolation of pseudolaric acids A and B,and their glucosides from the root bark of Pseudolarix kaempferi using high‐speed counter‐current chromatography

In order to provide the chemical markers for the quality control of herbal medicines, four diterpenoids, pseudolaric acids A and B (PAA and PAB), and their glucosides were isolated from the methanol extract of the Chinese herb Pseudolarix kaempferi using high‐speed counter‐current chromatography (HSCCC). The diphase solvent system was n‐hexane/EtOAc/MeOH/H₂O which was used at two ratios (5:5:5:5 and 1:9:4:6 by volume) in the separation of pseudolaric acids and their glycosides, respectively. As a result, PAA (14 mg), PAB (129 mg), PAA‐O‐β‐D ‐glucopyranoside (8 mg, PAAG), and PAB‐O‐β‐D ‐glucopyranoside (42 mg, PABG) were obtained from 0.5 g of the crude extract. Their purities were determined to be above 97% by HPLC analysis. Their chemical structures were confirmed by ¹H and ¹³C NMR analysis or HPLC comparison with the reference compounds.     

Sensitive determination of phenols in environmental water samples with SPE packed with bamboo carbon prior to HPLC

Bamboo carbon, an inexpensive, readily available material, has attracted great attention in recent years because of adsorptive properties. In this paper, the potential of bamboo carbon as a SPE adsorbent for the determination of phenols, was investigated. Phenols are important environmental contaminants that may adversely affect human health. Parameters influencing extraction efficiency, including type of eluent, eluent volume, amount of adsorbent, as well as sample pH, volume, and flow rate were investigated and optimized. The optimized results exhibited excellent linear relationships between peak area and phenol concentrations over the range of 2.0–100 ng/mL, with precision between 2.2–7.2%. The LODs were 0.06–0.4 ng/mL for the eight phenols tested. The proposed method has been successfully applied to the analysis of several real‐world environmental water samples. These results indicate that bamboo carbon may be used as a novel SPE adsorbent for the concentration and determination of phenols in real environmental water samples.