Molybdenum nitride based hybrid cathode for rechargeable lithium-O2 batteries

Molybdenum nitride/nitrogen-doped graphene nanosheets (MoN/NGS) are synthesized and used as an alternative O(2) electrode for Li-O(2) batteries. In comparison with electrocatalysts proposed previously, this hybrid cathode exhibits a high discharge potential (around 3.1 V) and a considerable specific capacity (1490 mA h g(-1), based on carbon + electrocatalyst).     

Sol–gel based synthesis of ultrafine tetragonal BaTiO3

Ultrafine tetragonal BaTiO₃ nanocrystals have been prepared by a sol–gel based method. By adjusting the volume ratio of H₂O/DEG (diethylene glycol) in the solutions, hydrolysis rate of tetra-n-butyl titanate was strongly inhibited and the particle size could be controlled as small as 4–8 nm. The powder X-ray diffraction and transmission electron microscopy characterizations exhibit that the nanocrystals are spherical and well crystallized. The Raman spectrum shows the products are composed of the orthorhombic phase and tetragonal phase. The Fourier transform infrared spectrum revealed that a surface modification layer was formed around the BaTiO₃ nanocrystals, which can prevent them from aggregation and help to form a stable, high solid content sol.     

Synthetic Transformations of Sulfur‐Substituted 4‐Quinolizidinones

Sulfur‐substituted 4‐quinolizidinones, previously prepared by aza‐Diels‐Alder reactions and ring‐closing metathesis, are now subjected to further synthetic transformations. Formal synthesis of cermizine C and 5‐epi‐cermizine C, and some other useful reactions have been achieved.     

A UFLC‐MS/MS method with a switching ionization mode for simultaneous quantitation of polygalaxanthone III,four ginsenosides and tumulosic acid in rat plasma: application to a comparative pharmacokinetic study in normal and Alzheimer's disease rats

A fast, sensitive and reliable ultra fast liquid chromatography‐tandem mass spectrometry (UFLC‐MS/MS) method has been developed and validated for simultaneous quantitation of polygalaxanthone III (POL), ginsenoside Rb1 (GRb1), ginsenoside Rd (GRd), ginsenoside Re (GRe), ginsenoside Rg1 (GRg1) and tumulosic acid (TUM) in rat plasma after oral administration of Kai‐Xin‐San, which plays an important role for the treatment of Alzheimer's disease (AD). The plasma samples were extracted by liquid–liquid extraction using ethyl acetate–isopropanol (1:1, v/v) with salidrdoside as internal standard (IS). Good chromatographic separation was achieved using gradient elution with the mobile phase consisting of methanol and 0.01% acetic acid in water. The tandem mass spectrometric detection was performed in multiple reaction monitoring mode on 4000Q UFLC‐MS/MS system with turbo ion spray source in a negative and positive switching ionization mode. The lower limits of quantification were 0.2–1.5 ng/ml for all the analytes. Both intra‐day and inter‐day precision and accuracy of analytes were well within acceptance criteria (±15%). The mean absolute extraction recoveries of analytes and IS from rat plasma were all more than 60.0%. The validated method has been successfully applied to comparing pharmacokinetic profiles of analytes in normal and AD rat plasma. The results indicated that no significant differences in pharmacokinetic parameters of GRe, GRg1 and TUM were observed between the two groups, while the absorption of POL and GRd in AD group were significantly higher than those in normal group; moreover, the GRb1 absorbed more rapidly in model group. The different characters of pharmacokinetics might be caused by pharmacological effects of the analytes. Copyright © 2013 John Wiley & Sons, Ltd.     

Collective Total Synthesis of Englerin A and B,Orientalol E and F,and Oxyphyllol: Application of the Organocatalytic [4+3] Cycloaddition Reaction

The concise collective total synthesis of englerin A and B, orientalol E and F, and oxyphyllol has been accomplished in 10–15 steps, with the total synthesis of orientalol E and oxyphyllol being achieved for the first time. The success obtained was enabled by the realization of the [4+3] cycloaddition reaction of 9 and 10 . Other features of the synthesis include 1) the intramolecular Heck reaction to access the azulene core, 2) the epoxidation–S_N2′ reduction sequence to access the allylic alcohol, 3) the efficient regioselective and stereoselective formal hydration of the bridging C?C bond in the synthesis of englerins, and 4) the late‐stage chemo‐ and stereoselective C? H oxidation in the synthesis of orientalol E. The total synthesis of these natural products has enabled the structural revision of oxyphyllol and established the absolute stereochemical features of the organocatalytic [4+3] cycloaddition reaction. The identification of 5 as the natural product oxyphyllol, the success in converting 5 to orientalol E, along with the fact that englerins and oxyphyllol were isolated from plants of the same genus Phyllanthus gives support to our proposed biosynthetic pathways. This work may enable detailed biological evaluations of these natural products and their analogues and derivatives, especially of their potential in the fight against renal cell carcinoma (RCC).     

单分散磁性Fe3O4纳米粒子修饰石墨烯的制备及应用

通过油相热分解法在石墨烯(Gr)的表面修饰单分散的Fe3O4纳米颗粒,然后将二亚乙基三胺五乙酸(DTPA)通过多巴胺(DPA)化学键合到到Gr复合物表面,制备了新型磁性纳米复合材料Gr@Fe3O4-DPA-DTPA,采用X射线衍射、透射电镜、振动样品磁强计、傅里叶红外、拉曼和紫外光谱等技术对该材料进行了表征。结果表明,材料对水中的芳香族化合物和重金属离子具有很强的吸附能力,对水中的萘和Cu2+的吸附容量分别达到207.9和72.2mg/g。     

聚苯胺/醋酸纤维素复合膜的制备及其超级电容特性

通过电化学原位聚合法制备多孔网状结构的聚苯胺(PANI)/醋酸纤维素(CA)复合膜电极,该复合膜的内层(与电极接触的一面)呈墨绿色,外层呈白色。采用原子力显微镜(AFM)、扫描电镜(SEM)、红外光谱(FTIR)对其形貌和化学组成进行表征。通过循环伏安、恒电流充放电和电化学阻抗研究了复合膜电极的超级电容特性。结果表明,多孔网状结构的PANI/CA复合材料具有良好的电容性能,其比电容可达到410F/g,并且该超级电容器具有较小的内阻和较好的循环稳定性,300次循环后,容量仍维持在342F/g,比电容的保持率为83.4%。     

反相高效液相色谱柱前衍生荧光法测定肠粘膜中的谷氨酰胺

以邻苯二甲醛及３－巯基丙酸为衍生试剂,５０ｍｍｏｌ／Ｌ磷酸缓冲液（ｐＨ７．０）－乙腈（９４∶６,Ｖ／Ｖ）为流动相,在ＬｉｃｈｒｏｓｏｒｂＲＰ１８（１５０ｍｍ×４．６ｍｍｉ．ｄ．,５μｍ）柱上,研究并建立了测定动物肠粘膜中谷氨酰胺（Ｇｌｎ）的柱前衍生荧光ＲＰ－ＨＰＬＣ法。样品与衍生剂按４∶１进行衍生反应,Ｅｘ＝２３０ｎｍ,Ｅｍ＝３８９ｎｍ;流速为２．０ｍＬ／ｍｉｎ。Ｇｌｎ的保留时间为３．１５８ｍｉｎ,检测限为２５μｍｏｌ／Ｌ（Ｓ／Ｎ＝３．５）,线性范围为５０～３２００μｍｏｌ／Ｌ,ｒ＝０．９９９６。     

Dynamics of ice nucleation on water repellent surfaces

Prevention of ice accretion and adhesion on surfaces is relevant to many applications, leading to improved operation safety, increased energy efficiency, and cost reduction. Development of passive nonicing coatings is highly desirable, since current antiicing strategies are energy and cost intensive. Superhydrophobicity has been proposed as a lead passive nonicing strategy, yet the exact mechanism of delayed icing on these surfaces is not clearly understood. In this work, we present an in-depth analysis of ice formation dynamics upon water droplet impact on surfaces with different wettabilities. We experimentally demonstrate that ice nucleation under low-humidity conditions can be delayed through control of surface chemistry and texture. Combining infrared (IR) thermometry and high-speed photography, we observe that the reduction of water-surface contact area on superhydrophobic surfaces plays a dual role in delaying nucleation: first by reducing heat transfer and second by reducing the probability of heterogeneous nucleation at the water-substrate interface. This work also includes an analysis (based on classical nucleation theory) to estimate various homogeneous and heterogeneous nucleation rates in icing situations. The key finding is that ice nucleation delay on superhydrophobic surfaces is more prominent at moderate degrees of supercooling, while closer to the homogeneous nucleation temperature, bulk and air-water interface nucleation effects become equally important. The study presented here offers a comprehensive perspective on the efficacy of textured surfaces for nonicing applications.     

Sequosempervirin A, a novel spirocyclic compound from Sequoia sempervirens

A novel spirocyclic compound (4R)-4-(4-hydroxy-benzyl) spiro [4,5] dec-1-en-8-ol (sequosempervirin A) was isolated from the branches and leaves of Sequoia sempervirens. Its structure and relative stereochemistry were mainly determined by MS, 2D NMR and X-ray means, which is the first naturally occurring norlignan containing one spirocycle with C6 (cyclohexane)-C2-C3-C6 skeleton.