A blue-phase liquid crystal lens array based on dual square ring-patterned electrodes

We propose a blue-phase liquid crystal (BPLC) lens array based on dual square ring-patterned electrodes. A high dielectric constant layer is used to smoothen out the horizontal electric field and reduce the operating voltage. By creating a potential difference between the dual square ring-patterned electrodes, gradient electric fields are generated and lens-like phase profile is obtained. Besides, the focal length of the BPLC lens is adjustable with voltage changes and all simulation results indicate that the BPLC lens array is polarisation-insensitive.     

铈对低镍铬锰氮奥氏体不锈钢晶间腐蚀的影响研究

针对不同稀土Ce含量的低镍铬锰氮奥氏体不锈钢,采用电化学动电位再活化法和Cu-CuSO4-16%H2SO4热酸浸泡法研究了两种热处理状态下不同铈含量试样的晶间腐蚀程度。研究结果表明:两种热处理状态下,未添加稀土试样腐蚀最严重。不同稀土含量的试样750℃敏化处理2 h比650℃敏化处理2 h腐蚀程度略重。从两组试验的金相显微组织照片和EPR活化率数据来看,两种热处理状态稀土Ce含量为0.053%时奥氏体不锈钢抗晶间腐蚀能力最强,但当铈含量增加到0.067%时,试样腐蚀又开始恶化。     

Oxygen Reduction Reaction in a Droplet on Graphite: Direct Evidence that the Edge Is More Active than the Basal Plane

Carbon‐based metal‐free electrocatalysts for the oxygen reduction reaction (ORR) in alkaline medium have been extensively investigated with the aim of replacing the commercially available, but precious platinum‐based catalysts. For the proper design of carbon‐based metal‐free electrocatalysts for the ORR, it would be interesting to identify the active sites of the electrocatalyst. The ORR was now studied with an air‐saturated electrolyte solution droplet (diameter ca. 15 μm), which was deposited at a specified position either on the edge or on the basal plane of highly oriented pyrolytic graphite. Electrochemical measurements suggest that the edge carbon atoms are more active than the basal‐plane ones for the ORR. This provides a direct way to identify the active sites of carbon materials for the ORR. Ball‐milled graphite and carbon nanotubes with more exposed edges were also prepared and showed significantly enhanced ORR activity. DFT calculations elucidated the mechanism by which the charged edge carbon atoms result in the higher ORR activity.     

Towards Vaporized Molecular Discrimination: A Quartz Crystal Microbalance (QCM) Sensor System Using Cobalt‐Containing Mesoporous Graphitic Carbon

A recent study on nanoporous carbon based materials (J. Am. Chem. Soc.­ 2012 , 134, 2864) showed that the presence of abundant graphitized sp² carbon species in the frameworks led to higher affinity for aromatic hydrocarbons than their aliphatic analogues. Herein, improved understanding of the sensitive and selective detection of aromatic substances by using mesoporous carbon (MPC)‐based materials, combined with a quartz crystal microbalance (QCM) sensor system, was obtained. MPCs were synthesized by direct carbonization of mesoporous polymers prepared from resol through a soft templating approach with Pluronic F127. The carbon‐based frameworks can be graphitized through the addition of a cobalt source to the precursor solution, according to the catalytic activity of the cobalt nanoparticles formed during the carbonization process. From the Raman data, the degree of the graphitization was clearly increased by increasing the cobalt content and elevating the carbonization temperature. From a QCM study, it was proved that the highly graphitized MPCs exhibited a higher affinity for aromatic hydrocarbons than their aliphatic analogues. By increasing the degree of graphitization in the carbon‐based pore walls, the MPCs showed both larger adsorption uptake and faster sensor response towards toxic benzene and toluene vapors.     

SnS2 Nanoplatelet@Graphene Nanocomposites as High‐Capacity Anode Materials for Sodium‐Ion Batteries

Na‐ion batteries have been attracting intensive investigations as a possible alternative to Li‐ion batteries. Herein, we report the synthesis of SnS₂ nanoplatelet@graphene nanocomposites by using a morphology‐controlled hydrothermal method. The as‐prepared SnS₂/graphene nanocomposites present a unique two‐dimensional platelet‐on‐sheet nanoarchitecture, which has been identified by scanning and transmission electron microscopy. When applied as the anode material for Na‐ion batteries, the SnS₂/graphene nanosheets achieved a high reversible specific sodium‐ion storage capacity of 725 mA h g^?1, stable cyclability, and an enhanced high‐rate capability. The improved electrochemical performance for reversible sodium‐ion storage could be ascribed to the synergistic effects of the SnS₂ nanoplatelet/graphene nanosheets as an integrated hybrid nanoarchitecture, in which the graphene nanosheets provide electronic conductivity and cushion for the active SnS₂ nanoplatelets during Na‐ion insertion and extraction processes.     

A one‐dimensional coordination polymer with a capped [Cu4O4] cubane core assembled from 2‐(hydroxymethyl)pyridine

The one‐dimensional coordination polymer catena‐poly[[[di‐μ₂‐acetato‐tetrakis[μ₃‐(pyridin‐2‐yl)methanolato]tetracopper(II)]‐di‐μ₂‐diacetamidato] acetonitrile monosolvate], {[Cu₄(C₆H₆NO)₄(CH₃COO)₂(C₂N₃)₂]·CH₃CN}_n, has been prepared from the direct reaction of 2‐(hydroxymethyl)pyridine with Cu(OAc)₂·H₂O (OAc⁻ is acetate) in a methanol–acetonitrile mixture. The four Cu centres are bridged by four O atoms from discrete (pyridin‐2‐yl)methanolate ligands and two acetate groups, forming a capped [Cu₄O₄] cubane core. Each core is doubly bridged to each of two adjacent cores by [N(CN)₂]⁻ anions, resulting in one‐dimensional chains. The magnetic properties of the complex were also studied.     

Synthesis,structure characterization,and thermochemistry of the coordination compounds of pyridine-2,6-dicarboxylic acid with several metals (Ca and Co)

Two solid state complexes of pyridine-2,6-dicarboxylate with Ca²⁺ and Co²⁺ ions, Ca₂(DPC)₂(H₂O)₆(H₂DPC)₂(s) and Co(DPC)₂·Co(H₂O)₅·2H₂O(s), were synthesized. X-ray crystallography was applied to characterize the crystal structures of the two complexes. The molecular and cell stacking structures of the two complexes were shown; the crystal data and refinement details were summarized, and the selected bond lengths and angles of the title complexes were listed. Low-temperature heat capacities of the two complexes were measured with an automated adiabatic calorimeter in the temperature ranging from 78 to 380 K. Two polynomial equations of experimental molar heat capacities as a function of the temperature were obtained by the least-squares method. The smoothed molar heat capacities and thermodynamic functions of the complexes were calculated based on the fitted polynomial equations. In addition, thermodynamic properties of the two complexes were compared.     

A novel nitrite sensor fabricated through anchoring nickel-tetrahydroxy-phthalocyanine and polyethylene oxide film onto glassy carbon electrode by a two-step covalent modification approach

In this paper, we present a two-step covalent modification approach to fabricate a novel nitrite sensor through anchoring nickel-tetrahydroxy-phthalocyanine (NiPc(OH)₄) and polyethylene oxide (PEO) onto a glassy carbon electrode (GCE). The surface morphology of the prepared NiPc(OH)₄/PEO composite films under different dry conditions was characterized by scanning electron microscopy (SEM). The electrochemical behavior of NiPc(OH)₄/PEO composite film modified GCE toward the catalytic oxidation of nitrite in pH 7.0 phosphate buffer solution (PBS) was investigated by cyclic voltammetry (CV). After drying under an infrared lamp, the fabricated sensor showed a pronounced electrocatalytic activity improvement toward the oxidation of nitrite and led to a significant decrease in the anodic overpotentials compared with bare GCE, which should be ascribed to the synergistic effect of NiPc(OH)₄ and PEO, as well as the enlarged electrochemical effective surface area after drying. Using differential pulse voltammetry (DPV), the sensor gave a linear response to nitrite over the concentration range of 0.1–5,300 μM, with a detection limit of 0.0522 μM. The nitrite sensor exhibits good sensitivity, selectivity, and stability and has been applied for the determination of nitrite in water samples.     

An improved LC‐MS/MS method for simultaneous determination of 1,5‐dicaffeoylquinic acid and its active metabolites in human plasma and its application to a pharmacokinetic study in patients

In this study, a sensitive, selective and reproducible liquid chromatography–tandem mass spectrometry method for the simultaneous determination of 1,5‐dicaffeoylquinic acid (1,5‐DCQA) and its active metabolites, 1‐caffeoyl‐5‐feruoylquinic acid and 1,5‐O‐diferuoylquinic acid, in human plasma, using puerarin as internal standard, was developed and validated. Analytes were extracted from plasma samples by liquid–liquid extraction with ethyl acetate, separated on a C₁₈ reversed‐phase column with water containing 5 mM ammonium acetate and acetonitrile as the mobile phase and detected by electrospray ionization mass spectrometry in negative selected reaction monitoring mode. The accuracy and precision of the method were acceptable and linearity was good over the range 1–200 ng/mL for each analyte. In addition, the selectivity, extraction recovery and matrix effect were satisfactory too. The validated LC‐MS/MS method was successfully applied to phase II clinical pharmacokinetic study of 1,5‐DCQA in patients. Copyright © 2010 John Wiley & Sons, Ltd.