高活性α-二亚胺基Ni(Ⅱ)配合物的合成、表征及其催化乙烯聚合研究

设计并合成了一种新型的含有强供电子、大体积基团tert-butyl的α-二亚胺配体1及其Ni(Ⅱ)配合物2,并利用1H NMR,13C NMR,元素分析,FT-IR,XPS对其进行了表征.配合物2/氯化二乙基铝(DEAC)组成的催化体系催化乙烯聚合显示了非常高的活性,最高可达3.15×108 g PE/(mol·Ni·h·MPa).所得聚乙烯的支化度也较高,最高可达131branches/1000C.并研究了聚合条件如聚合反应温度、Al/Ni物质的量比、反应时间等因素对催化剂活性的影响.在反应温度为5℃,Al/Ni物质的量比为600时,该催化体系催化乙烯聚合活性最高.采用1H NMR,GPC,DSC,TG分别对聚合物进行了表征.     

壳聚糖-树枝状大分子杂化物的研究进展

壳聚糖-树枝状大分子杂化物主要包括壳聚糖-(聚酰胺-胺)[CS-PAMAM]、壳聚糖-聚乙烯亚胺[CS-PEI]、壳聚糖-3,4,5-三(p-十二烷氧基苄氧基)苯甲酸[CS-DOBOB酸]、壳聚糖-3,4,5-三(p-十二烷氧基-m-甲氧基苄氧基)苯甲酸(DOVOB酸)、壳聚糖-聚丙三醇(PGLD)等树枝状大分子杂化物。壳聚糖-树枝状大分子杂化物具有良好的水溶性、生物可降解性、抗菌性、吸附性和热致液晶性等性能。壳聚糖-树枝状大分子杂化物的用途广泛,可作为金属离子的吸附剂、治疗高胆红素血症的吸附材料、新型荧光材料、抗菌剂和抗凝血剂等。本文综述了壳聚糖-树枝状大分子杂化物的研究进展,并展望了其未来研究方向和应用前景。     

湿地水质与水系浮游细菌多样性关联研究

城市湿地水质受人类活动影响,其水系浮游细菌群落多样性也因水质状况不同而变化.以杭州西溪湿地国家公园为研究区,分析人类活动特征差异对河道水质及浮游细菌群落多样性的影响,测定溶解氧、氨氮、硝氮、总氮、总磷等主要理化指标,运用聚合酶链式反应与变性梯度凝胶电泳(PCR-DGGE)技术,分析各水样中浮游细菌群落多样性,通过主成分分析与典型对应分析等统计手段,比较各项理化指标与细菌群落结构的相关性.研究结果表明:湿地河道水质受人类活动影响显著,呈中度~重度富营养化;河道水域内细菌群落总体多样性较高,且多样性指数与硝态氮、总氮、TSI指数、电导率呈极显著负相关(r<-0.7,p<0 .01),与水温呈极显著正相关(r>0.8,p<0.01),相较于硝态氮、总氮等单项指标,综合营养状态指数与细菌多样性指数间具有最高负相关性(r=-0.90,p<0.01).浮游细菌群落结构变化受多种理化指标共同影响,其中限制性营养元素氨氮为主要调控因子.     

New nickel(II) diimine complexes bearing phenyl and sec‐phenethyl groups: synthesis,characterization and ethylene polymerization behaviour

A series of nickel(II) catalysts containing phenyl and chiral sec‐phenethyl groups, {[(4‐R₁‐2‐R₂C₆H₂N?C)₂Nap]NiBr₂} (Nap: 1,8‐naphthdiyl, R₁ = Me, R₂ = Ph ( 3a ); R₁ = Me, R₂ = sec‐phenethyl ( 3b ); R₁ = Cl, R₂ = sec‐phenethyl ( 3c ); R₁ = Me, R₂ = Me ( 3d ) were synthesized and characterized. All organic compounds were fully characterized by FT‐IR and NMR spectroscopy and elemental analysis. The single crystal for X‐ray crystallography was isolated from 3a in CH₂Cl₂/n‐hexane under air; the crystal structure showed a binuclear complex 3a ′, in which each nickel atom was six‐coordinate. The two nickel atoms together with two bromine atoms form a planar four‐membered ring, with a bromine and H₂O axial ligands. These complexes, activated by diethylaluminum chloride and chiral nickel pre‐catalysts rac‐ 3c , exhibited good activities (up to 2.85 × 10⁶ g PE (mol Ni h bar)^?1) for ethylene polymerization, and produced polyethylene products with a high degree of branching (up to 117 branched per 1000 carbons) at high temperature. The type and amount of branches of the polyethylenes obtained were determined by ¹H and ¹³C NMR spectroscopy. Copyright © 2014 John Wiley & Sons, Ltd.     

Rechargeable Room‐Temperature Na–CO2 Batteries

Developing rechargeable Na–CO₂ batteries is significant for energy conversion and utilization of CO₂. However, the reported batteries in pure CO₂ atmosphere are non‐rechargeable with limited discharge capacity of 200 mAh g^?1. Herein, we realized the rechargeability of a Na–CO₂ battery, with the proposed and demonstrated reversible reaction of 3 CO₂+4 Na?2 Na₂CO₃+C. The battery consists of a Na anode, an ether‐based electrolyte, and a designed cathode with electrolyte‐treated multi‐wall carbon nanotubes, and shows reversible capacity of 60000 mAh g^?1 at 1 A g^?1 (≈1000 Wh kg^?1) and runs for 200 cycles with controlled capacity of 2000 mAh g^?1 at charge voltage <3.7 V. The porous structure, high electro‐conductivity, and good wettability of electrolyte to cathode lead to reduced electrochemical polarization of the battery and further result in high performance. Our work provides an alternative approach towards clean recycling and utilization of CO₂.     

Evaluation and application of a mixed‐mode chromatographic stationary phase in two‐dimensional liquid chromatography for the separation of traditional Chinese medicine

In this study, two mixed‐mode chromatography stationary phases (C8SAX and C8SCX) were evaluated and used to establish a two‐dimensional liquid chromatography system for the separation of traditional Chinese medicine. The chromatographic properties of the mixed‐mode columns were systematically evaluated by comparing with other three columns of C8, strong anion exchanger, and strong cation exchanger. The result showed that C8SAX and C8SCX had a mixed‐mode retention mechanism including electrostatic interaction and hydrophobic interaction. Especially, they were suitable for separating acidic and/or basic compounds and their separation selectivities could be easily adjusted by changing pH value. Then, several off‐line 2D‐LC systems based on the C8SAX in the first dimension and C8SAX, C8SCX, or C8 columns in the second dimension were developed to analyze a traditional Chinese medicine—Uncaria rhynchophylla. The two‐dimensional liquid chromatography system of C8SAX (pH 3.0) × C8SAX (pH 6.0) exhibited the most effective peak distribution. Finally, fractions of U. rhynchophylla prepared from the first dimension were successfully separated on the C8SAX column with a gradient pH. Thus, the mixed‐mode stationary phase could provide a platform to separate the traditional Chinese medicine in practical applications.     

A continuous process for the reductive deoxygenation of aromatic ketones over Cu30Cr10/γ-Al2O3

A continuous process for reduction of aromatic ketones to the corresponding aromatic alkanes over Cu₃₀Cr₁₀/??-Al₂O₃ was established in a fixed-bed reactor. A series of aromatic ketones were examined, and all of the corresponding aromatic hydrocarbons were obtained in more than 95% yield. The catalysts were characterized by X-ray diffraction, X-ray photoelectron spectroscopy, and H₂-temperature programmed reduction. Cu⁰ is believed to be the active center of the catalyst. Cr was found to have an important effect on catalytic activity and stability.     

用定量会聚束电子衍射技术对二十面体AlPdMn准晶结构的优化

对n0，n1，b1和d0等4个位置上的7个原子面，用位置对称性允许的面谐函数描述原子面边界的形状和大小，用定量会聚束电子衍射技术对描述这7个原子面的形状与大小的15个参数进行了精修，得到了一个新的描述二十面体AlPdMn准晶结构的高维空间模型．由这个模型，在三维物理空间用切割法得到了比不考虑棱边中点d0处原子面的球形模型和非球形模型更加完整的原子结构，原子间距不合理的情况得以消除．通过解析式表述的这一模型，与用菱形多面体和91个参数描述原子面的6维团簇模型相比适用性更强．     

二氧化锰纳米材料水热合成及形成机理研究进展

不同晶型和形貌MnO2纳米材料由于具有离子筛、分子筛、催化和电化学等许多特殊的物理和化学性质,因而在吸附材料、催化材料、锂离子二次电池的正极材料和新型磁性材料等领域显示了广阔的应用前景。纵观合成MnO2纳米材料的各种方法,水热合成由于简单、易于控制,并且能够有效控制其晶型、形貌和尺寸,深受研究者的青睐。本文结合国内外的...