Hierarchical Mn3O4 Anchored on 3D Graphene Aerogels via C−O−Mn Linkage with Superior Electrochemical Performance for Flexible Asymmetric Supercapacitor

Flexible asymmetric supercapacitors are more appealing in flexible electronics because of high power density, wide cell voltage, and higher energy density than symmetric supercapacitors in aqueous electrolyte. In virtues of excellent conductivity, rich porous structure and interconnected honeycomb structure, three dimensional graphene aerogels show great potential as electrode in asymmetric supercapacitors. However, graphene aerogels are rarely used in flexible asymmetric supercapacitors because of easily re-stacking of graphene sheets, resulting in low electrochemical activity. Herein, flower-like hierarchical Mn₃O₄ and carbon nanohorns are incorporated into three dimensional graphene aerogels to restrain the stack of graphene sheets, and are applied as the positive and negative electrode for asymmetric supercapacitors devices, respectively. Besides, a strong chemical coupling between Mn₃O₄ and graphene via the C-O-Mn linkage is constructed and can provide a good electron-transport pathway during cycles. Consequently, the asymmetric supercapacitor device shows high rate cycle stability (87.8 % after 5000 cycles) and achieves a high energy density of 17.4 μWh cm⁻² with power density of 14.1 mW cm⁻² (156.7 mW cm⁻³) at 1.4 V.     

Influence of peripheral alkyl chain length on the mesomorphic behaviours of hexasubstituted triphenylene 2,3-dicarboxylic esters

A comparative study of our established synthetic approaches to hexasubsituted triphenylenes 2,3-dicarboxylic esters containing four identical β-alkoxy and two adjacent β-alkoxycarbonyl side chains shows that the phase behaviours of small-sized discotic liquid crystals can be tailored over a wide range by simply varying the length of the peripheral alkyl chains. All the prepared esters in two series were observed to form a single hexagonal columnar phase, except for Tp4-1 having four β-butyloxy and two adjacent β-methoxycarbonyl chains which displays two columnar mesophase behaviours with a transition from the columnar plastic phase to hexagonal columnar phase. A significant difference between the two mesophase was observed in the variable temperature X-ray diffraction studies, and the mesophase assignment was also confirmed by polarising optical microscopy and differential scanning calorimetry. Moreover, the prepared esters in each series display the general trend of decreasing clearing temperature upon increasing alkoxy or alkoxycarbonyl chains length. The intermediate triphenylene 2,3-dicarboxylic acids were also found not only to exhibit columnar hexagonal mesophase over a narrower temperature range by maintaining high melting and clearing points but also to form organogel on mixing with toluene or dichloromethane with the assistance of hydrogen bonding.     

Crown ether complexes of sodium and potassium 2-(benzotriazol-2-yl)phenolates: Synthesis and catalysis towards the ring-opening polymerization of rac-lactide

Crown ether complexes of sodium and potassium 2-(benzotriazol-2-yl)phenolates were synthesized and characterized. In the presence of BnOH these complexes are highly active catalysts for the controlled ring-opening polymerization of rac-lactide. The polymerizations are iso-selective and the P_m of polylactide reached 0.77 when the polymerization was performed in toluene at ?60°C; whereas heterorich-polylactide was obtained when the polymerization was carried out in CH₂Cl₂ or THF.     

脱铝八面沸石的研究(Ⅳ)——异丙苯催化裂化

以脉冲微型反应技术研究了脱铝八面沸石对异丙苯的催化裂化行为,并与反应条件下表面酸性进行了关联。样品裂化活性随骨架Si/Al比增加呈山峰形变化,Si/Al=5.38时最大;反应条件下酸中心数随脱铝深度增加却单调降低。动力学数据表明,样品裂化反应速度常数与强质子酸中心数随骨架Si/Al比增加具有平行的山峰形变化规律,Si/Al比为8.87附近的样品最高。     

Three new oleanene glycosides from Sophora flavescens.

Three new oleanene glycosides, sophoraflavosides II-IV (2-4) were isolated together with sophoraflavoside I (1) as the corresponding methyl ester forms from Sophorae Radix, the fresh roots of Sophora flavescens AITON (Leguminosae). Their structures have been elucidated as oxytrogenin 3-O-alpha-L-rhamnopyranosyl-(1-->2)-beta-D-galactopyranosyl-(1-->2)-beta -D- glucuronopyranoside (2), 3-O-alpha-L-rhamnopyranosyl-(1-->2)-beta-D-galactopyranosyl-(1-->2)-beta -D-glucuronopyranosyl oxytrogenin 22-O-alpha-L-arabinopyranoside (3) and 3-O-alpha-L-rhamnopyranosyl-(1-->2)-beta-D-galactopyranosyl-(1-->2)-beta -D-glucuronopyranosyl oxytrogenin 22-O-beta-D-glucopyranosyl-(1-->2)-alpha-L-arabinopyranoside (4), along with unambiguous characterization as 3 beta,22 beta,24-trihydroxyolean-12-en-29-oic acid for their sapogenol, named oxytrogenin (5) on the bases of chemical reactions and spectral analyses.