The First Online Capillary Electrophoresis-Microscale Thermophoresis (CE-MST) Method for the Analysis of Dynamic Equilibria—The Determination of the Acidity Constant of Fluorescein Isothiocyanate

This article presents the first successful application of a capillary electrophoresis-microscale thermophoresis tandem technique (CE-MST) for determining the values of equilibrium constant, realized by connecting online the CE and MST instruments using a fused-silica capillary. The acid-base dissociation of fluorescein isothiocyanate, expressed by the acidity constant value (pK_a), was used as a model. The measurement procedure consisted of introducing a mixture containing the analyte and a deliberately added interferent into the CE capillary, electrophoretic separation of the analyte from the interferent, the detection of the analyte with a CE-integrated detector, detection with a MST detector, and then stopping the flow temporarily by turning off the voltage source to conduct the thermophoretic measurement. The analysis of migration times, peak areas and MST responses obtained concurrently for the same sample allowed us to determine the pK_a value using three independent methods integrated within one instrumentation. The analyte was effectively separated from the interferent, and the acidity values turned out to be consistent with each other. An attempt was also made to replace the standard commercial CE instrument with a home-made portable CE setup. As a result, the similar pK_a value was obtained, at the same time proving the possibility of increasing cost efficiency and reducing energy consumption. Overall, the CE-MST technique has a number of limitations, but its unique analytical capabilities may be beneficial for some applications, especially when sample separation is needed prior to the thermophoretic measurement.     

Phenolic Constituents,Antioxidant and Cytoprotective Activities,Enzyme Inhibition Abilities of Five Fractions from Vaccinium dunalianum Wight

The bud of Vaccinium dunalianum Wight has been traditionally consumed as health herbal tea by “Yi” people in Yunnan Province, China, which was locally named “Que Zui tea”. This paper studied the chemical constituents of five fractions from Vaccinium dunalianum, and their enzyme inhibitory effects of α-glucosidase and pancreatic lipase, antioxidant activity, and cytoprotective effects on H₂O₂-induced oxidative damage in HepG2 cells. The methanol extract of V. dunalianum was successively partitioned with petroleum ether (PF), chloroform (CF), ethyl acetate (EF), n-butanol (BF), and aqueous (WF) to obtain five fractions. The chemical profiling of the five fractions was analyzed by ultra-high-performance liquid chromatography coupled with a tandem mass spectrometry (UHPLC-MS/MS), and 18 compounds were tentatively identified. Compared to PF, CF, BF and WF, the EF revealed the highest total phenols (TPC) and total flavonoids (TFC), and displayed the strongest enzyme inhibition ability (α-glucosidase and pancreatic lipase) and antioxidant capacity (DPPH, ABTS and FRAP). Furthermore, these five fractions, especially EF, could effectively inhibit reactive oxygen species (ROS) production and cell apoptosis on H₂O₂-induced oxidative damage protection in HepG2 cells. This inhibitory effect might be caused by the up-regulation of intracellular antioxidant enzyme activity (CAT, SOD, and GSH). The flavonoids and phenolic acids of V. dunalianum might be the bioactive substances responsible for enzyme inhibitory, antioxidant, and cytoprotective activities.     

Improvement of characteristics of an InGaN light-emitting diode by using a staggered AlGaN electron-blocking layer

The optical and physical properties of an InGaN light-emitting diode (LED) with a specific design of a staggered AlGaN electron-blocking layer (EBL) are investigated numerically in detail. The electrostatic field distribution, energy band, carrier concentration, electroluminescence (EL) intensity, internal quantum efficiency (IQE), and the output power are simulated. The results reveal that this specific design has a remarkable improvement in optical performance compared with the design of a conventional LED. The lower electron leakage current, higher hole injection efficiency, and consequently mitigated efficiency droop are achieved. The significant decrease of electrostatic field at the interface between the last barrier and the EBL of the LED could be one of the main reasons for these improvements.     

一种蓝色聚合物激光材料

聚合物作为一种有机发光材料,由于在平板显示和光电子器件中的良好应用前景而受到广泛研究［１～２］．近年来,一个重要进展是在聚合物中观测到了受激发射（简称Ｐｏｌｙ－ｍｅｒ激光）现象［３～６］．Ｐｏｌｙｍｅｒ激光最早是在溶液中实现的［３～４］．作为一种新型...     

Measuring powder flowability with a modified Warren Spring cohesion tester

The measurement of powder flowability is a major concern for most industrial processes that deal with the handling of bulk solids as raw materials,intermediates,or products.The development of devices that measure the flowability of non-aerated powders has not progressed as rapidly as might have been hoped since most research activities have been based on various types of shear testers intended to aid the design of hoppers.A new flowability indicator named as weighted cohesion (WS) is established using newly...     

Determination of phenolic whitening agents in cosmetics by micellar electrokinetic capillary chromatography with amperometric detection

A sensitive method for simultaneous determination of six phenolic whitening agents,including arbutin, phenol,resorcinol,hydroquinone,kojic acid,and salicylic acid in cosmetics has been developed using micellar electrokinetic capillary chromatography with amperometric detection（MECC-AD）.Effects of several factors,such as the pH value and concentration of running buffer,potential applied to the working electrode,separation voltage,and injection time were investigated to obtain optimum conditions for separation and detection.With a 75 cm long fused-silica capillary tube,well-defined separation of six phenolic compounds was achieved in 10mmol/L SDS/40 mmol/L H₃BO₃-Na₂B₄O₇ running buffer（pH 9.0）.Good linear relationship was obtained for each analyte over three orders of magnitude with correlation coefficients（r2） between 0.9985 and 0.9994,and the detection limit（S/N=3） ranged from 0.04μg/mL to 0.45μg/mL The proposed method has been successfully applied for the determination of phenolic whitening agents in real cosmetic samples with satisfactory results,providing an alternative monitoring method for cosmetics safety regulation.     

微米及纳米丝光沸石分子筛上二甲醚羰基化反应的积碳分析

对比研究了在传统微米尺寸和新结构纳米丝光沸石催化剂上二甲醚羰基化合成乙酸甲酯的反应行为.结果表明,通过减小分子筛的尺寸到纳米水平,可以有效提高反应物和产物到达或者脱离反应活性位的效率,从而提高了二甲醚的转化率;更重要的是,抑制了硬积碳的生成,使催化剂保持了更高的稳定性.     

仿生制备有机-无机复合微囊固定化葡萄糖氧化酶

将层层自组装技术与仿生矿化技术相结合,由聚苯乙烯磺酸钠、聚二甲基二烯丙基氯化铵和二氧化硅成功制备(聚苯乙烯磺酸钠-聚二甲基二烯丙基氯化铵)₂-二氧化硅复合微囊.采用扫描电子显微镜、红外光谱和热重对微囊的形貌和化学结构进行了表征.以该复合微囊作为理想载体固定化葡萄糖氧化酶.结果表明,固定于复合微囊中的葡萄糖氧化酶的热稳定性、pH稳定性、操作稳定性得到了提高;在最适条件下,复合微囊固定化葡萄糖氧化酶的酶活回收率为72.85%,米氏常数是游离葡萄糖氧化酶的2.21倍.复合微囊在化学/生物催化、药物/基因传递系统和生物传感器应用方面具有一定的潜能.     

纳米碳材料非金属催化的研究进展

纳米碳材料直接作为催化剂的非金属碳催化是目前材料科学与催化领域的前沿方向之一.相对于传统金属催化剂,纳米碳材料催化剂具有高效环保、低能耗、耐腐蚀等优点.在烃类转化、化学品合成、能源催化等领域表现出优异的催化性能和发展潜力.综述了近年来纳米碳非金属催化研究的最新进展,主要包括新型纳米碳材料的表面性质、催化特性、反应机理和宏观制备等关键问题,并对纳米碳催化存在的挑战和前景进行了展望.     

碳纳米管担载纳米Ir催化生物质基乙酰丙酸合成γ-戊内酯

以碳纳米管(CNTs)担载Ir纳米粒子为催化剂进行生物质基平台化合物乙酰丙酸(LA)选择加氢制备γ-戊内酯(GVL)的研究,并利用X射线衍射、X射线光电子能谱和透射电镜表征了使用前后的Ir/CNT催化剂,探讨了影响LA催化加氢制GVL反应性能的因素和该反应的可能路径.结果表明,与Ru,Rh和Pd等传统铂族金属相比,Ir/CNT催化剂不但可在温和条件下(50℃,2.0 MPa,H₂)实现LA至GVL的完全转化,且可对多类直接源于生物质水解的含等量LA/甲酸的“真实”体系实现GVL的高效选择合成.