加压毛细管电色谱法高效分离分析葛根多糖中的单糖

葛根多糖具有抗氧化、抗肿瘤等众多生物活性,对葛根多糖进行单糖组成分析对其活性研究具有重要意义。该研究利用响应面分析法考察了超声辅助提取法中液料比、超声温度、超声时间和超声功率对葛根多糖提取率的交互影响,并拟合数据得到多元二次回归方程。同时建立了柱前衍生加压毛细管电色谱检测糖类的方法,对分离8种中性单糖的色谱条件进行了探索与优化,并将此方法应用于两种葛根实际样品的单糖组成测定。响应面分析结果表明,4个试验因素中,超声温度对两种葛根多糖提取率的影响程度最大,其次为液料比,超声时间和超声功率影响程度较小。结合软件预测分析得到的最佳条件及设备实际情况,确定葛根多糖的最佳提取工艺条件为：超声温度90℃,粉葛多糖液料比20 mL/g,柴葛多糖液料比40 mL/g,超声时间30 min,超声功率180 W。优化后的色谱分离条件为：采用Halo-2.7 μm核壳型C18填料毛细管色谱柱,以乙腈-50 mmol/L pH 4.1的醋酸铵水溶液（18：82,v/v）为流动相,在250 nm波长下检测,施加电压-20 kV。在此条件下可以实现24 min内对葡萄糖等8种中性单糖衍生物的快速分离,相比传统液相色谱方法大大提升了分离检测速度和分离柱效。方法学考察表明此方法具有较好的线性关系和良好的重复性。对实际样品分离鉴定表明,粉葛多糖主要由葡萄糖、甘露糖、鼠李糖和岩藻糖组成,4种单糖物质的量之比为1.00：0.16：0.14：0.07;柴葛多糖主要由葡萄糖和甘露糖组成,2种单糖物质的量之比为1.00：0.70。该研究为单糖化合物快速高效分离检测提供了新方法,并为葛根多糖单糖组成分析提供了参考。     

Electrochemical behavior of Mg-doped 7LiFePO4–Li3V2(PO4)3 composite cathode material for lithium-ion batteries

Mg-doping effects on the electrochemical property of LiFePO₄–Li₃V₂(PO₄)₃ composite materials, a mutual-doping system, are investigated. X-ray diffraction study indicates that Mg doping decreases the cell volume of LiFePO₄ in the composite. The cyclic voltammograms reveal that the reversibility of the electrode reaction and the diffusion of lithium ion is enhanced by Mg doping. Mg doping also improves the conductivity and rate capacity of 7LiFePO₄–Li₃V₂(PO₄)₃ composite material and decreases the polarization of the electrode reaction. The discharge capacity of the Mg-doped composite was 93 mAh?g^?1 at the current density of 1,500 mA?g^?1, and Mg-doped composite has better discharge performance than the original 7LiFePO₄–Li₃V₂(PO₄)₃ composite at low temperature, too. At ?30 °C, the discharge capacity of Mg-doped LFVP is 89 mAh?g^?1, higher than that of the original composite. Electrochemical impedance spectroscopy study shows that Mg²⁺ doping could enhance the electrochemical activity of 7LiFePO₄–Li₃V₂(PO₄)₃ composite. Mg doping has a positive influence on the electrochemical performance of the LiFePO₄–Li₃V₂(PO₄)₃ composite material.     

The phase change property of lauric acid confined in carbon nanotubes as nano-encapsulated phase change materials

Lauric acid (LA) impregnates in carbon nanotubes (CNTs), resulting in nano-encapsulated phase change materials (PCMs). TEM and DSC results both indicate that the filling of LA into CNTs is realized by the vacuum infiltration method. A further study of nano-encapsulated PCMs at the molecular level is investigated by molecular dynamics simulations. From the axial view of CNTs, LA molecules always keep a circular distribution inside CNTs with a radius of about 4.8 Å. The analysis on radial distribution function, the end-to-end distance and the torsion angle simultaneously verifies that the order degree of LA molecules is improved due to the nano-confined effect of CNTs. The diffusion coefficient of LA is enhanced in CNTs. The energy flux and thermal conductivity of LA molecules in CNTs are higher than those of pure LA at the same temperature. These results fully indicate the heat and mass transfer of LA in CNTs could be enhanced. The current research could contribute to a deep understanding nanoscale thermal science and to potential application in heat dissipation of nanodevices.

     

手性双提蓝钴卟啉配合物催化二氧化碳对环氧的不对称环加成（英文）

绿色化学是当今化学科学研究的前沿领域.仿生催化是绿色合成技术和方法学研究的一个重要方面.生物质和酶分子在酶催化转化过程中的"构-效"关系可以通过仿生催化进行模拟研究.CO_2作为温室气体的主要成分是造成全球气候变暖的主要因素,但它同时也是C1化学的重要原料.利用CO_2与有机环氧化合物通过偶联反应制备有机环碳酸酯或聚碳酸酯则是CO_2化学研究的热点之一,并已经取得了长足的进步.但是运用手性催化剂对此反应进行不对称环加成得到手性环碳酸酯的研究不多.本文首次设计并合成了具有双提篮结构的手性钴卟啉螯合物.其中的提篮部分由手性联萘酚(S或R)和L-苯丙氨酸组成,从卟啉骨架的meso位引入,首先制备了两种手性结构的自由卟啉配体(6a,7a);然后与醋酸钴反应得到两种二价钴卟啉手性配合物(6b,7b),加入醋酸后,通过空气氧化得到三价钴卟啉手性催化剂(6c,7c).采用紫外、红外光谱、质谱和核磁共振(包括二维NMR)等技术对得到的卟啉中间化合物、配合物和催化剂进行了详细的表征,确定了化合物的结构.将得到的三价钴卟啉配合物作为手性催化剂用于CO_2和环氧化合物的不对称环加成反应.结果表明,提篮的手性基团对小分子的环氧化合物环氧丙烷具有手性选择性,在低温-20°C下,可以得到大于50%的ee值.同时由于提篮与卟啉平面空间的有限性,导致分子体积较大的环氧化合物与CO_2的反应很慢,也没有发现其对环碳酸酯的对映选择性.我们相信本工作对于合成手性卟啉分子及其在不对称催化中的应用具有一定的意义.     

绿色安全染发剂的研究进展及展望

染发已成为人们的日常需要与时尚选择。目前广泛使用的化学染发剂主要成分为对苯二胺类物质,其引起的致敏性、致癌性与致突变性等问题日益凸显。生物质染发剂及仿生染发剂与化学合成染发剂相比具有安全低毒、资源可再生、环境友好等优点。本文以近年来国内外对绿色安全染发剂的研究为基础,从头发的组成结构和显色机理出发,从生物质染发剂以及仿生染发剂两个方面总结了绿色安全染发剂的研究现状与发展瓶颈,并对其应用前景进行了展望,旨在为安全无毒、绿色健康染发剂的研发提供参考。     

An Engineered Superhydrophilic/Superaerophobic Electrocatalyst Composed of the Supported CoMoSx Chalcogel for Overall Water Splitting

The development of high‐efficiency electrocatalysts for large‐scale water splitting is critical but also challenging. In this study, a hierarchical CoMoS_x chalcogel was synthesized on a nickel foam (NF) through an in situ metathesis reaction and demonstrated excellent activity and stability in the electrocatalytic hydrogen evolution reaction and oxygen evolution reaction in alkaline media. The high catalytic activity could be ascribed to the abundant active sites/defects in the amorphous framework and promotion of activity through cobalt doping. Furthermore, the superhydrophilicity and superaerophobicity of micro‐/nanostructured CoMoS_x/NF promoted mass transfer by facilitating access of electrolytes and ensuring fast release of gas bubbles. By employing CoMoS_x/NF as bifunctional electrocatalysts, the overall water splitting device delivered a current density of 500 mA cm^?2 at a low voltage of 1.89 V and maintained its activity without decay for 100 h.     

Fabrication of ZIF‐8@Polyphosphazene core‐shell structure and its efficient synergism with ammonium polyphosphate in flame‐retarding epoxy resin

A novel zeolitic imidazolate framework (ZIF‐8) nanoparticles@polyphosphazene (PZN) core‐shell architecture was synthesized, and then, ZIF‐8@PZN and ammonium polyphosphate (APP) were applied for increasing the flame retardancy and mechanical property of epoxy resin (EP) through a cooperative effect. Herein, ZIF‐8 was used as the core; the shell of PZN was coated to ZIF‐8 nanoparticles via a polycondensation method. The well‐designed ZIF‐8@PZN displayed superior fire retardancy and smoke suppression effect. The synthesized ZIF‐8@PZN observably raised the flame retardancy of EP composites, which could be demonstrated by thermogravimetric analysis (TGA) and a cone calorimeter test (CCT). The chemical structure of ZIF‐8@PZN was characterized by X‐ray diffraction (XRD), X‐ray photoelectron spectroscopy (XPS), and transmission electron microscopy (TEM). Compared with pure epoxy, with the incorporation of 3 wt% ZIF‐8@PZN and 18 wt% APP into the EP, along with 80.8%, 72.6%, and 64.7% decreased in the peak heat release rate (pHRR), the peak smoke production rate (pSPR), and the peak CO production rate (pCOPR), respectively. These suggested that ZIF‐8@PZN and APP generated an intumescent char layer, and ZIF‐8@PZN can strengthen the char layer, resulting in the enhancement in the flame resistance of EP.