Constructing Built-in Electric Field in Heterogeneous Nanowire Arrays for Efficient Overall Water Electrolysis

Efficient bifunctional electrocatalysts for hydrogen and oxygen evolution reactions are key to water electrolysis. Herein, we report a built-in electric field (BEF) strategy to fabricate heterogeneous nickel phosphide-cobalt nanowire arrays grown on carbon fiber paper (Ni₂P-CoCH/CFP) with large work function difference (ΔΦ) as bifunctional electrocatalysts for overall water splitting. Impressively, Ni₂P-CoCH/CFP exhibits a remarkable catalytic activity for hydrogen and oxygen evolution reactions to obtain 10 mA cm⁻², respectively. Moreover, the assembled lab-scale electrolyzer driven by an AAA battery delivers excellent stability after 50 h electrocatalysis with a 100 % faradic efficiency. Computational calculations combining with experiments reveal the interface-induced electric field effect facilitates asymmetrical charge distributions, thereby regulating the adsorption/desorption of the intermediates during reactions. This work offers an avenue to rationally design high-performance heterogeneous electrocatalysts.     

Determination of the migration of 8 benzophenones in food contact materials and products by HPLC-MS / MSEI北大核心CSCD

建立了高效液相色谱-串联质谱法测定食品接触材料及制品中8种二苯甲酮类物质迁移量的方法。样品经过食品模拟物浸泡后,水、4%乙酸、10%乙醇、20%乙醇、50%乙醇模拟物直接进样,95%乙醇模拟物用水按照1:4比例稀释后进样,橄榄油和异辛烷模拟物用甲醇-水混合溶液萃取后进样。采用C₁₈柱分离,用甲醇-0.1%甲酸水溶液为流动相梯度洗脱,质谱采用正离子多反应监测（MRM）模式运行。本方法在8种食品模拟物中的定量限为0.01～0.20 mg/kg;在0.04～0.80 mg/kg, 0.2～2.0 mg/kg, 0.6～3.0 mg/kg线性范围内相关系数良好（R≥0.9958）;加标实验结果显示相对标准偏差（RSD）为0.61%～7.8%。该方法可用于食品接触材料及制品中二苯甲酮类物质迁移量的测定。     

Impedance Analysis of Single Melanoma Cells in Microfluidic Devices

The electrical impedance analysis of single cells can provide information on cells’ pathological condition in various environments. Cell electrical properties are affected by factors such as the location, adhesion, and size of the cell. The proposed microfluidic device captures a single cell, maintains growth conditions, and allows single‐melanoma‐cell impedance to be measured using an impedance analyzer and a function generator. The rate of impedance variation (ROIV) can be used to determine cell growth conditions. Cellular apoptosis affects cell size and membrane surface area, and thus the electrical properties of cells. At 24 h without Antrodia cinnamomea (AC) addition, ROIV was 15.23 %, 17.04 %, and 12.60 % at temperatures of 34 °C, 37 °C, and 40 °C, respectively. At 24 h and 37 °C, ROIV was 17.04 %, 40.37 %, and 45.02 % for AC concentrations of 0, 20, and 40 µL/mL, respectively. The results show that the cell impedance variation of cells cultured without AC is much lower than that of cells cultured with AC. Regarding cellular morphology, with AC addition, the cells shrank obviously after 24 h, whereas they barely shrank without AC addition.     

A mechanism for water splitting and hydrogen absorbing functions of metal–oxide layered hydrogen storage materials studied by means of ion beam analysis

This review describes a study of catalytic functions of water splitting at the surface and hydrogen gas emitting from the bulk of metal–oxide layered materials as well as hydrogen storage materials as its application by means of the ion beam analysis techniques. First are described a microscopic model for water splitting at the oxide surface and mass balance equations for hydrogen atoms in the bulk. The latter is a mathematical expression of a one‐way diffusion model proposed for an anomalous isotope effect in D–H and H–D replacements of both deuterium (D) implanted into perovskite oxide ceramics by protium (H) in H₂O vapour and the vise versa. The latter model brings about finding of catalytic functions of water splitting at the surface and hydrogen gas emitting from the bulk. Second, experimental results on the anomalous isotope effect are presented and the D–H replacement rates are described in detail. Subsequently are shown results on H₂ gas emission measured with a Bach method, which give a clear evidence for the water splitting and hydrogen gas emitting catalytic functions of the oxide surface. Finally, we present experimental data on the hydrogen absorption and emission characteristics of the metal–oxide layered hydrogen storage materials as an application of the water splitting and hydrogen absorbing catalysts. Copyright © 2014 John Wiley & Sons, Ltd.     

Ab initio Quantum Mechanics/Molecular Mechanics Molecular Dynamics Simulation of CO in the Heme Distal Pocket of Myoglobin

Myoglobin has important biological functions in storing and transporting small diatomic molecules in human body. Two possible orientations of carbon monoxide (CO) in the heme distal pocket (named as B₁ and B₂ states) of myoglobin have been experimentally indicated. In this study, ab initio quantum mechanics/molecular mechanics (QM/MM) molecular dynamics simulation of CO in myoglobin was carried out to investigate the two possible B states. Our results demonstrate that the B₁ and B₂ states correspond to Fe…CO (with carbon atom closer to iron center of heme) and Fe…OC (with oxygen atom closer to Fe), by comparing with the experimental infrared spectrum. QM electrostatic polarization effect on CO brought from the protein and solvent environment is the main driving force, which anchors CO in two distinctive orientations and hinders its rotation. The calculated vibrational frequency shift between the state B₁ and B₂ is 13.1 cm^-1, which is in good agreement with experimental value of 11.5 cm^-1. This study also shows that the electric field produced by the solvent plays an important role in assisting protein functions by exerting directional electric field at the active site of the protein. From residue-based electric field decomposition, several residues were found to have most contributions to the total electric field at the CO center, including a few charged residues and three adjacent uncharged polar residues (namely, HIS64, ILE107, and PHE43). This study provides new physical insights on rational design of enzyme with higher electric field at the active site.     

光涡旋偶极子经半屏衍射后的演化

推导出寄居于高斯光束中的光涡旋偶极子经过半屏衍射后的解析传输公式.利用所得公式对光涡旋偶极子经半屏衍射后的演化做了详细研究.结果表明,与自由空间中光涡旋偶极子演化相比较,衍射场中会出现多对光涡旋偶极子,湮没方式与离轴量有关.随离轴参数的变化,偶极子出现不同的演化特性,但在演化过程中,拓扑电荷守恒. 关键词： 光涡旋偶极子 半屏衍射 拓扑电荷     

119Sn electric field gradients in model clusters of chalcogenide glasses

Calculations of ¹¹⁹Sn electric field gradients (EFG) have been performed using the Extended Hückel approximation on characteristic molecular clusters simulating possible types of sites in chalcogenide glasses. The motivation for these calculations derives from theoretical concepts on varying near neighbor relationships in these types of glasses, and from recent ¹¹⁹Sn Mössbauer experiments on Sn-doped Ge_x(Se or S)_1–x bulk glasses which reveal three types (A, B and C) of chemically inequivalent sites, with distinct values and composition dependences for their isomer shifts and quadrupole splittings. The model clusters chosen for the calculations were the ethane-like (Ge₂Se₃)_n quasi-one-dimensional chains of varying lengths which have been proposed as possible sources of the B site. In addition, calculations were also carried out on several additional types of clusters, in order to help in interpreting the results for the chains. We find that the magnitude of the quadrupole splitting in isolated linear ethane-like chains is very small, and almost independent of the particular site along the chain at which Sn replaces Ge. It therefore seems unlikely that such isolated linear clusters would be the source of the B sites. These sites are more likely to be related to distortions of the ethane-like clusters into non-linear configurations, as well as interactions with neighboring clusters, as forced by the constraints of the packing in the structure of the glass.     

A moving boundary model motivated by electric breakdown: II. Initial value problem

An interfacial approximation of the streamer stage in the evolution of sparks and lightning can be formulated as a Laplacian growth model regularized by a ‘kinetic undercooling’ boundary condition. Using this model we study both the linearized and the full nonlinear evolution of small perturbations of a uniformly translating circle. Within the linear approximation analytical and numerical results show that perturbations are advected to the back of the circle, where they decay. An initially analytic interface stays analytic for all finite times, but singularities from outside the physical region approach the interface for t→∞, which results in some anomalous relaxation at the back of the circle. For the nonlinear evolution numerical results indicate that the circle is the asymptotic attractor for small perturbations, but larger perturbations may lead to branching. We also present results for more general initial shapes, which demonstrate that regularization by kinetic undercooling cannot guarantee smooth interfaces globally in time.     

电热板消解法与微波消解法测定大气颗粒物Cu、Pb元素的对比

采用电热板消解法与微波消解法两种前处理消解方法,测定了青岛小麦岛环境监测站大气颗粒物滤膜样品的Cu、Pb含量,并对测定结果进行了分析对比.发现两种消解方法测定的Cu、Pb含量的分析精密度均较好,只是微波消解法测定值略小于电热板消解法,测定Cu元素时,两种方法不存在显著性差异,可等效使用,而测定Pb元素时,两种方法略存在差异.     

Spontaneous emission coupling factors in planar micro-cavity lasers with distributed Bragg reflectors

In this article, a considerable value of spontaneous emission factor is estimated based on the spontaneous emission radiation patterns in micro-cavity lasers. After the spontaneous emission for a dipole in the micro-cavity is studied, the confinements of vacuum fields and electrons are considered together for a quantum well in the micro-cavity laser. The TE mode and TM mode spontaneous emission spectra are presented for a single quantum well embedded in a planar micro-cavity laser at 300 K. The results show that the TE mode spontaneous emission spectrum is enhanced, whereas the TM mode spontaneous emission is suppressed greatly. The maximum values obtained for the spontaneous emission coupling factors are 0.2 and 0.0055 for a dipole and a quantum well planar micro-cavity laser with distributed Bragg reflectors, respectively.