聚碳酸1,2-丙二酯的碱催化水解研究

研究了高分子量聚碳酸1,2-丙二酯的碱催化水解反应,并通过核磁共振谱仪和气相色谱质谱联用仪对降解反应产物的解析,发现碱催化聚碳酸1,2-丙二酯水解是无规断链反应和解拉链反应共同作用的结果.结果表明高分子量聚碳酸1,2-丙二酯的碱催化水解是制备低分子量聚碳酸1,2-丙二酯的方法之一.     

Mekongenines A and B, two new alkaloids from Bousigonia mekongensis

Mekongenine A (1) possessing an unprecedented structure constituted from the union of a rare 2,7-seco eburnamine half and an aspidospermine alkaloid, together with a new bisindole alkaloid, mekongenine B (2), consisting of an eburnamine-aspidospermine type skeleton, was isolated from Bousigonia mekongensis. Their structures were elucidated by means of spectroscopic methods and those of 2 were further confirmed by X-ray diffraction. The absolute configurations of 1 and 2 were determined by comparison of quantum chemical TDDFT calculated and experimental ECD spectra. Mekongenines A (1) and B (2) exhibited cell growth inhibitory activities against various human cancer cell lines.     

双金属氰化物/稀土配合物催化二氧化碳和环氧丙烷的共聚合

使用双金属氰化物/稀土配合物复合催化剂催化二氧化碳和环氧丙烷共聚合,其催化效率比双金属氰化物催化剂有显著提高,得到了数均相对分子质量大于1.0×105的聚合物。研究了复合催化剂的组成(如稀土的种类、稀土与锌的比例(Ln/Zn)、稀土配合物中酸根离子的酸性等)对共聚反应的影响,同时研究了反应体系的压力及反应时间对催化活性的影响。采用Y(CCl3COO)3稀土金属配合物有利于共聚反应的进行。当n(Y)/n(Zn)=6、聚合4 h后,其催化活性比单纯的双金属氰化物提高了31.5%,聚合物的相对分子质量则没有太大变化,而副产物碳酸丙烯酯的质量分数低于2%,而在该温度下单独采用稀土三元催化剂时副产物碳酸丙烯酯的生成量通常在10%以上。聚合物中碳酸酯含量低于双金属氰化物的催化产物,说明稀土配合物只是起到活化金属与环氧丙烷配位的作用,没有提高共聚物的碳酸酯含量,整个共聚合反应依然遵循双金属氰化物催化的共聚反应机理。     

Blue-light emitting diodes and flat display based on poly (p-phenylenevinylene) copolymers

Copolymers containing alternating flexible aliphatic blocks and rigid poly (p-phenylenevinylene) (PPV) blocks were synthesized and characterized. It was found that the fluorescent intensity increases with increasing length of the flexible blocks. Bright blue-light emitting diodes were fabricated using PPV copolymers as electroluminescent layers. The devices show 190 cd/m² light-emitting brightness at 460 nm and 15 V turn-on voltage. The effects of oxadiawle derivative PBD and tris(8-hydroxyquinoline) aluminum Alq₃ electron-transporting layers on the luminance and stability of the devices are discussed. Project supported by the National Natural Science Foundation of China, PCLCC, the State Comission of Science and Technology of China (863-715-002-0130) and the Chinese Acadeny of Sciences (KJ951-A1-501-01)     

Adsorption of UO2 2+ on poly(N,N-diethylacrylamide-co-acrylic acid): effects of pH, ionic strength, initial uranyl concentration, and temperature

We prepared poly(N,N-diethylacrylamide-co-acrylic acid) (P(DEA-co-AA)) microgels which could efficiently remove UO₂ ²⁺ from aqueous solutions. In this study, the effect of adsorption parameters such as pH value, adsorbent dose, shaking time, and temperature has investigated. It is found that the pseudo-second-order model is more suitable for our experiment. The adsorption kinetic data indicated that the chemical adsorption was the swiftness processes, the adsorption equilibrium could be achieved within 30 min. And there are very good correlation coefficients of linearized equations for Langmuir isotherm model, which indicated that the sorption isotherm of the hydrogel for UO₂ ²⁺ can be fitted to the Langmuir isotherm model. The adsorption process was spontaneous (?G ⁰ < 0) and exothermic (?H ⁰ < 0). The adsorbed UO₂ ²⁺ can be desorbed effectively by 0.1 M HNO₃ and the adsorption capacity is not significantly reduced after five cycles. Present study suggests that this P(DEA-co-AA) can be used as a potential adsorbent for sorption UO₂ ²⁺ and also provide a simple, fast separation method for removal of UO₂ ²⁺ ions from aqueous solution.     

应用顶空-气相离子迁移谱分析百合发酵乳的风味物质

按方法采集百合鳞茎经蒸制、打浆制成熟制样品(ZBH)。另取纯牛奶经杀菌、接种、发酵12h制得原味酸奶(SN-1/2)。另按方法制得百合酸奶(SN-3/4)和5个不同发酵时间(8,10,12,14,16h)的百合发酵酸奶(BHSN)。分别取上述4种样品各1.0g,分别按工作条件进行顶空采样并引入气相离子迁移谱分析系统进行分析。根据所测得数据,并经NIST数据库检索,在以上4种样品的挥发性组分中共鉴定了24种化合物。将这些化合物的信号峰强度进一步分析,可得到其中15种挥发物成分在不同样本中存在明显差异。根据所测得4种样品的挥发物中的一些特征组分或其信号峰强度的差异可对所涉及样品作出区别。例如正己醇等可作为ZBH的特征性组分。此外,对样品的风味物质进行正交偏最小二乘法判别分析(OPLS-DA),还可准确区分上述4种样品,以及不同发酵时间的BHSN的主要风味挥发成分的类别和含量,从而判断和选择适当的发酵时间。     

水热法合成YLiF4∶Er3+的上转换发光

用水热法合成了YLiF4∶Er3+,Er3+浓度变化范围为 0%～5%.在室温下,测试了所有样品在200～1200 nm间的吸收光谱.当 Er3+浓度为2%(Er-2样品)时,由吸收光谱计算得到的J-O参数为Ω2=1.05×10-20 cm2,Ω4=1.25×10-20 cm2和Ω6=1.35×10-20 cm2.在980 nm激发下,测试了所有样品的上转换发光光谱,发光强度随Er3+ 浓度增加而增长.当Er3+ 浓度小于1.5%,激发态吸收是主要的上转换发光机制.当Er3+ 浓度高于1.5%时,上转换机制包括激发态吸收和能量传递.在室温下,Er-2样品的能级2H11/2的寿命是205 μs,4S3/2的是205 μs,4F9/2是188 μs.根据实验数据和计算所得的跃迁几率,计算了4S3/2能级和4F9/2能级的量子效率,分别是27.9%和10.7%,表明两者都具有很高的量子效率.     

Improving the denitration performance and K-poisoning resistance of the V2O5-WO3/TiO2 catalyst by Ce4+ and Zr4+ co-doping

A series of V₂O₅-WO₃/TiO₂-ZrO₂, V₂O₅-WO₃/TiO₂-CeO₂, and V₂O₅-WO₃/TiO₂-CeO₂-ZrO₂ catalysts were synthesized to improve the selective catalytic reduction (SCR) performance and the K-poisoning resistance of a V₂O₅-WO₃/TiO₂ catalyst. The physicochemical properties were investigated by using XRD, BET, NH₃-TPD, H₂-TPR, and XPS, and the catalytic performance and K-poisoning resistance were evaluated via a NH₃-SCR model reaction. Ce⁴⁺ and Zr⁴⁺ co-doping were found to enhance the conversion of NO_x, and exhibit the best K-poisoning resistance owing to the largest BET-specific surface area, pore volume, and total acid site concentration, as well as the minimal effects on the surface acidity and redox ability from K poisoning. The V₂O₅-WO₃/TiO₂-CeO₂-ZrO₂ catalyst also presents outstanding H₂O + SO₂ tolerance. Finally, the in situ DRIFTS reveals that the NH₃-SCR reaction over the V₂O₅-WO₃/TiO₂-CeO₂-ZrO₂ catalyst follows an L-H mechanism, and that K poisoning does not change the reaction mechanism.     

Conducting Polyaniline Confined in Semi‐Interpenetrating Networks

Conducting semi‐interpenetrating network composites with low conductivity percolation threshold were synthesized from waterborne conducting polyaniline (cPAn) and melamine‐urea resin. A perfect network of cPAn in the composite was observed by means of TEM (see Figure). The conductivity stability of cPAn in water was improved by confining the chain mobility of cPAn via in‐situ crosslinking of melamine‐urea resin. Cyclic voltammetry of the composites reveals electrochemical activities and reversibilities similarly to those of pure cPAn.