Synthesis of monodisperse oligocarbazoles-functionalized anthracenes with intense blue-emitting

New well-defined monodisperse oligocarbazoles-functionalized anthracenes An-OCZn (n = 1, 2, 3) have been synthesized through Suzuki cross-coupling reaction of the brominated oligocarbazoles and 9,10-bis(4,4,5,5-tetramethyl-1,3,2-dioxaborolan-2-yl)anthracene. They show good solubility in organic solvents, including dichloromethane, chloroform, toluene, ethyl acetate, and tetrahydrofuran. It should be noted that, in the case of An-OCZn, the formation of the excimer based on anthracene unit is suppressed completely due to the introduction of oligocarbazoles in 9,10-position of anthracene so that an intense blue-emitting has been afforded. In addition, the obtained An-OCZn exhibit good electrochemical and thermal stabilities. Thus, the oligocarbazoles-functionalized anthracenes can be a class of promising candidates for novel blue-emitting materials employed in OLEDs or related devices.     

Adsorption Mechanism of Comb Polymer Dispersants at the Cement/Water Interface

Comb polymers are commonly used as dispersants to stabilize highly concentrated cement suspensions. The effectiveness of such polymeric additives to stabilize these suspensions is determined to a large extent by the amount adsorbed. In this study we investigated the adsorption characteristics of various comb dispersant containing different graft densities on surfaces of cement particle. The effect of inorganic salts on their adsorption was also examined in order to elucidate their adsorption mechanism. The results show that the adsorption of comb polymer dispersants on cement surface conforms approximately to Langmuir's adsorption isotherm and the characteristic plateau A _s and adsorption free energy ΔG_ads are largely dependent on the anionic group content of the comb polymers. The A _s and ΔG_ads increase with increasing anionic group content. This information suggests that the adsorption of comb polymers on cement surfaces is dominated by electrostatic interaction between COO-groups on the comb polymers and the positive surface of the cement. This conclusion is supported by effects of inorganics such as calcium and sulfate ions, and diffuse reflectance FTIR spectroscopy. The implication of results for tuning polymers for the required performance in cement manufacture should be noted.     

Rational Design of an “OFF–ON” Phosphorescent Chemodosimeter Based on an Iridium(III) Complex and Its Application for Time‐Resolved Luminescent Detection and Bioimaging of Cysteine and Homocysteine

Biothiols, such as cysteine (Cys) and homocysteine (Hcy), play very crucial roles in biological systems. Abnormal levels of these biothiols are often associated with many types of diseases. Therefore, the detection of Cys (or Hcy) is of great importance. In this work, we have synthesized an excellent “OFF‐ON” phosphorescent chemodosimeter 1 for sensing Cys and Hcy with high selectivity and naked‐eye detection based on an Ir^III complex containing a 2,4‐dinitrobenzenesulfonyl (DNBS) group within its ligand. The “OFF‐ON” phosphorescent response can be assigned to the electron‐transfer process from Ir^III center and C^N ligands to the DNBS group as the strong electron‐acceptor, which can quench the phosphorescence of probe 1 completely. The DNBS group can be cleaved by thiols of Cys or Hcy, and both the ³M LCT and ³LC states are responsible for the excited‐state properties of the reaction product of probe 1 and Cys (or Hcy). Thus, the phosphorescence is switched on. Based on these results, a general principle for designing “OFF‐ON” phosphorescent chemodosimeters based on heavy‐metal complexes has been provided. Importantly, utilizing the long emission‐lifetime of phosphorescence signal, the time‐resolved luminescent assay of 1 in sensing Cys was realized successfully, which can eliminate the interference from the short‐lived background fluorescence and improve the signal‐to‐noise ratio. As far as we know, this is the first report about the time‐resolved luminescent detection of biothiols. Finally, probe 1 has been used successfully for bioimaging the changes of Cys/Hcy concentration in living cells.     

Designed Synthesis of Well‐Defined Pd@Pt Core–Shell Nanoparticles with Controlled Shell Thickness as Efficient Oxygen Reduction Electrocatalysts

Improving the electrocatalytic activity and durability of Pt‐based catalysts with low Pt content toward the oxygen reduction reaction (ORR) is one of the main challenges in advancing the performance of polymer electrolyte membrane fuel cells (PEMFCs). Herein, a designed synthesis of well‐defined Pd@Pt core–shell nanoparticles (NPs) with a controlled Pt shell thickness of 0.4–1.2 nm by a facile wet chemical method and their electrocatalytic performances for ORR as a function of shell thickness are reported. Pd@Pt NPs with predetermined structural parameters were prepared by in situ heteroepitaxial growth of Pt on as‐synthesized 6 nm Pd NPs without any sacrificial layers and intermediate workup processes, and thus the synthetic procedure for the production of Pd@Pt NPs with well‐defined sizes and shell thicknesses is greatly simplified. The Pt shell thickness could be precisely controlled by adjusting the molar ratio of Pt to Pd. The ORR performance of the Pd@Pt NPs strongly depended on the thickness of their Pt shells. The Pd@Pt NPs with 0.94 nm Pt shells exhibited enhanced specific activity and higher durability compared to other Pd@Pt NPs and commercial Pt/C catalysts. Testing Pd@Pt NPs with 0.94 nm Pt shells in a membrane electrode assembly revealed a single‐cell performance comparable with that of the Pt/C catalyst despite their lower Pt content, that is the present NP catalysts can facilitate low‐cost and high‐efficient applications of PEMFCs.     

阳离子聚丙烯酰胺水分散液的制备及表征

通过丙烯酰胺(AM)与甲基丙烯酰氧乙基三甲基氯化铵(DMC)的水相分散共聚合制得阳离子聚丙烯酰胺(CPAM)水分散液.以红外光谱(FTIR),核磁共振(1H-NMR),光学显微照片(OP)证实了产物结构与形成机理;研究了引发剂类型及用量,无机盐选择及用量,分散剂用量及单体配比对CPAM转化率、分子量及分散液黏度的影响.结果表明,采用2,2’-偶氮二[2-(2-咪唑啉-2-代)丙烷]二氢氯化物(VA-044)和过硫酸钾(KPS)/甲醛次硫酸氢钠(SFS)复合引发剂,在硫酸铵浓度28%～32%,同时添加少量硫酸锂或氯化钠,分散剂0.5%～1.5%(所有物质用量皆对总反应体系而言)条件下,可在高转化率同时得到分子量较高、流动性良好的CPAM水分散液.     

建筑用梳形共聚物分散剂溶液行为的光散射研究

采用激光光散射研究了一种主链为聚丙烯酸侧链为聚乙二醇的梳形共聚物分散剂的一些溶液行为.从静态光散射得出了较为合理的表观重均分子量、均方旋转半径等参数.动态光散射给出了流体力学半径分布及其角度和浓度依赖性.结合静态和动态光散射,上述梳形共聚物分散剂在溶液中的构象也得到初步的表征.通过与描述梳形聚合物的Gay-Raphae模型进行比较表明,这类梳形共聚物溶液在低盐离子和低pH值条件下存在聚集行为,形成以PAA主链为核PEG为壳层的类胶束聚集.     

Fluorescent sensor based on dimesitylborylthiophene derivative for probing fluoride and cyanide

A new D-π-A dimesitylboron derivative with terminal phenothiazine bridged by fluorenevinyl (PFTB) has been synthesized. It was found that PFTB could selectively recognize fluoride and cyanide anions by naked eyes. Upon addition of F⁻ and CN⁻, the color of the solution of PFTB in DCM turned to yellowish-green from yellow and strong green emitting was observed under UV light, while the emission of PFTB in DCM was weak. Moreover, the presence of 10 equiv of tetrabutylammonium salts of other anions, such as Cl⁻, Br⁻, I⁻, AcO⁻, HSO₄⁻, H₂PO₄⁻, could not lead to obvious changes of the UV–vis absorption and the fluorescent emission spectra of PFTB. The detection limits of PFTB towards F⁻ and CN⁻ were 7.52×10⁻⁸ mol/L and 6.12×10⁻⁸ mol/L in DCM, respectively. Therefore, the D-π-A type triarylborane derivatives can be used as ‘turn on’ fluorescent sensors for detecting F⁻ and CN⁻.     

含酰亚胺骨架的大环化合物合成、结构及其对阴离子的识别研究

在磷酸催化作用下,采用前体二胺N,N’-(2-胺基苯基)-2,6-二甲酰亚胺吡啶(1)和前体二醛1,4-二(2’-甲酰苯氧基)丁烷(2)进行缩合作用得到[1+1]Schiff碱大环化合物3,进一步将Schiff碱大环3还原得到饱和大环4.并采用1H NMR,IR,质谱和元素分析等技术对大环3和4的组成进行了表征.采用X射线单晶衍射技术测定了Schiff碱大环3的晶体结构,结果表明大环3具有扭曲的"8"字形结构.采用UV-vis光谱滴定技术对大环与系列阴离子的键合作用进行了考察,结果表明,Schiff碱大环3对F-离子有明显的选择性识别作用,并测定了该配位反应的配位比和平衡常数.     

Ultra‐fast LC–ESI‐MS/MS method for the simultaneous determination of six highly toxic Aconitum alkaloids from Aconiti kusnezoffii radix in rat plasma and its application to a pharmacokinetic study

A fast, sensitive, and efficient ultra‐fast LC–ESI‐MS/MS method was developed for the simultaneous quantitation of six highly toxic Aconitum alkaloids, that is, aconitine, mesaconitine, hypaconitine, benzoylaconine, benzoylmesaconine, and benzoylhypaconine, in rat plasma after oral administration of crude ethanol extracts from Aconiti kusnezoffii radix by ultrasonic extraction, reflux extraction for 1 h, and reflux extraction for 3 h, respectively. The separation of six Aconitum alkaloids and aminopyrine (internal standard) was performed on an InertSustain® C₁₈ column, and the quantification of the analytes was performed on a 4000Q ultra‐fast LC–MS/MS system with turbo ion spray source in the positive ion and multiple‐reaction monitoring mode. Absolute recoveries ranged within 65.06–85.1% for plasma samples. The intra‐ and interday precision and accuracy of analytes were satisfactory. The methods were validated with sensitivity reaching the lower LOQ for aconitine, mesaconitine, hypaconitine, benzoylaconine, benzoylmesaconine, and benzoylhypaconine, which were 0.025, 0.025, 0.050, 0.025, 0.025, and 0.100 ng/mL, respectively. The method was successfully applied to a pharmacokinetic study of six Aconitum alkaloids in rat plasma after oral administration of crude ethanol extracts from the raw root of Aconitum kusnezoffii Reichb. by three different extraction processes.     

One‐step strategy for the synthesis of a derivatized cyclodextrin‐based monolithic column

Derivatized β‐cyclodextrin (β‐CD) functionalized monolithic columns were prepared by a “one‐step” strategy using click chemistry. First, the intended derivatized β‐CD monomers were synthesized by a click reaction between propargyl methacrylate and mono‐6‐azido‐β‐CD and then sulfonation or methylation was carried out. Finally, monolithic columns were prepared through a one‐step in situ copolymerization of the derivatized β‐CD monomer and ethylene glycol dimethacrylate. The sulfated β‐CD‐based monolith was successfully applied to the hydrophilic interaction liquid chromatography separation of nucleosides and small peptides, while the methylated β‐CD‐functionalized monolith was useful for the separation of nonpolar compounds and drug enantiomers in capillary reversed‐phase liquid chromatography. The structures of the monomers were characterized by Fourier transform infrared spectroscopy and mass spectrometry. The physicochemical properties and column performance of monoliths were evaluated by scanning electron microscopy and micro high performance liquid chromatography. This strategy has considerable prospects for the preparation of other derivatized CD‐functionalized methacrylate monoliths.