Iridium‐Based Cubic Nanocages with 1.1‐nm‐Thick Walls: A Highly Efficient and Durable Electrocatalyst for Water Oxidation in an Acidic Medium

We report a highly active and durable water oxidation electrocatalyst based on cubic nanocages with a composition of Ir₄₄Pd₁₀, together with well‐defined {100} facets and porous walls of roughly 1.1 nm in thickness. Such nanocages substantially outperform all the water oxidation electrocatalysts reported in literature, with an overpotential of only 226 mV for reaching 10 mA cm^?2_geo at a loading of Ir as low as 12.5 μg_Ir cm^?2 on the electrode in acidic media. When benchmarked against a commercial Ir/C electrocatalyst at 250 mV of overpotential, such a nanocage‐based catalyst not only shows enhancements (18.1‐ and 26.2‐fold, respectively) in terms of mass (1.99 A mg^?1_Ir) and specific (3.93 mA cm^?2_Ir) activities, but also greatly enhanced durability. The enhancements can be attributed to a combination of multiple merits, including a high utilization efficiency of Ir atoms and an open structure beneficial to the electrochemical oxidation of Ir to the active form of IrO_x.     

新显色剂偶氮溴膦-PSN直接光度法测定离子吸附型稀土矿中稀土总量

新显色剂偶氮溴膦-PSN能在较强的酸性介质中与稀土元素形成稳定的蓝紫色络合物,最大吸收峰在667nm处,显色酸度范围宽,抗干扰能力强,其中允许钍存在5μg/25ml。本文拟定了直接光度法测定离子型稀土矿中稀土总量,方法简便快速,结果准确。     

Amperometric Ethanol Biosensor Based on Carbon Nanotubes Dispersed in Sol–Gel‐Derived Titania–Nafion Composite Film

Composite solution of sol–gel‐derived titania and perfluorosulfonated ionomer (Nafion) was used as a solubilizing agent for multiwalled carbon nanotubes (CNT) as well as an encapsulation matrix for alcohol dehydrogenase (ADH) for the fabrication of a highly sensitive and stable amperometric ethanol biosensor. ADH was immobilized within a thin film of CNT–titania–Nafion composite film coated on a glassy carbon electrode. Because of the mesoporous nature of the CNT–titania–Nafion composite film, the present biosensor exhibited remarkably fast response time within 2 s. The presence of CNT in the composite film increases not only the sensitivity of the ethanol biosensor but also the long‐term stability of the biosensor. The present biosensor responds linearly to ethanol in the wide concentration ranges from 1.0×10^?5 M to 3.0×10^?3 M with the sensitivity of 51.6 mA M^?1cm^?2. The present biosensor showed good long‐term stability with 75% of its activity retained after 4 weeks of storage in 50 mM phosphate buffer at pH 7.0.     

Inserting Thienyl Linkers into Conjugated Molecules for Efficient Multilevel Electronic Memory: A New Understanding of Charge‐Trapping in Organic Materials

The practical application of organic memory devices requires low power consumption and reliable device quality. Herein, we report that inserting thienyl units into D–π–A molecules can improve these parameters by tuning the texture of the film. Theoretical calculations revealed that introducing thienyl π bridges increased the planarity of the molecular backbone and extended the D–A conjugation. Thus, molecules with more thienyl spacers showed improved stacking and orientation in the film state relative to the substrates. The corresponding sandwiched memory devices showed enhanced ternary memory behavior, with lower threshold voltages and better repeatability. The conductive switching and variation in the performance of the memory devices were interpreted by using an extended‐charge‐trapping mechanism. Our study suggests that judicious molecular engineering can facilitate control of the orientation of the crystallite in the solid state to achieve superior multilevel memory performance.     

水热微乳液法合成BaLiF3：Er^3＋纳米微粒及表征

采用水/CTAB/正丁醇/正辛烷体系微乳液法及水热技术制备了BaLiF3∶Er^3＋纳米微粒。利用X射线衍射（XRD）、环境扫描电镜（ESEM）和红外荧光光谱等手段对所制备产物进行了表征。X射线衍射数据表明,所制备微粒与JCPDS标准卡片18-715吻合很好,利用谢乐公式计算所制备产物平均粒径在98.45 nm左右,与环境扫描电镜观察结果基本相同。BaLiF3∶Er^3＋纳米微粒的红外发射图谱由4个峰构成,最强峰位于1540 nm处,属于Er^3＋的f→f跃迁。     

沸石合成过程中的溶剂效应

沸石合成过程中的溶剂效应窦涛，冯芳霞，王晓钟，萧墉壮，曹景慧（太原工业大学精细化工研究所，太原０３００２４）刘建宇钟炳（山西省化工设计院，太原０３００２４）（中国科学院山西煤炭化学研究所，太原０３０００１）关键词ＺＳＭ－５，ＺＳＭ－３５，方钠石，溶剂...     

人工神经网络吸光光度法同时测定钛锆

在钛,锆-二溴羟基苯基荧光酮-CTMAB显色体系中,应用三层ANN—BP网络解析钛和锆的吸收光谱,不经分离吸光光度法同时测定钛和锆。钛和锆的表观摩尔吸光系数分别为ε_(547)=9.66×10~4,ε_(533)=1.80×10~5。同时测定合金钢中钛和锆,结果满意。使用改进的BP算法,避免了神经网络学习过程中可能产生的麻痹现象。提出了目标向量的简单变换方法及便于网络参数选择的收敛评价函数。     

Cu-DNAzyme facilitates highly sensitive immunoassay

Fast and sensitive antigen detection is important in biomedical research and development. Despite, being invented 48 years ago, the enzyme-linked immunosorbent assay (ELISA) remains one of the most successful and widely employed bioanalytical techniques in research and clinical diagnostics due to its reliability and simplistic design. Recently, nanotechnology has offered efficient signal reporting. In spite of some improvements in these systems, there are typically increased material costs involved and the need for expensive equipment or complicated chemical processes, thus negating any possible benefits over ELISA. Herein, we communicate a simple Cu-DNAzyme system for signal transduction of a CuO nanoparticle-labeled immunoassay. The reported immunoassay amplifies signal generation similar to traditional ELISA and is fast, simple, cost-effective, and sensitive, holding promise for biomedical applications and point-of-care testing.     

A new promising phosphor, Na3La2(BO3)3:Ln (Ln=Eu, Tb)

We present an efficient way to search a host for ultraviolet (UV) phosphor from UV nonlinear optical (NLO) materials. With the guidance, Na₃La₂(BO₃)₃ (NLBO), as a promising NLO material with a broad transparency range and high damage threshold, was adopted as a host material for the first time. The lanthanide ions (Tb³⁺ and Eu³⁺)-doped NLBO phosphors have been synthesized by solid-state reaction. Luminescent properties of the Ln-doped (Ln=Tb³⁺, Eu³⁺) sodium lanthanum borate were investigated under UV ray excitation. The emission spectrum was employed to probe the local environments of Eu³⁺ ions in NLBO crystal. For red phosphor, NLBO:Eu, the measured dominating emission peak was at 613 nm, which is attributed to ⁵D₀-⁷F₂ transition of Eu³⁺. The luminescence indicates that the local symmetry of Eu³⁺ in NLBO crystal lattice has no inversion center. Optimum Eu³⁺ concentration of NLBO:Eu³⁺ under UV excitation with 395 nm wavelength is about 30 mol%. The green phosphor, NLBO:Tb, showed bright green emission at 543 with 252 nm excited light. The measured concentration quenching curve demonstrated that the maximum concentration of Tb³⁺ in NLBO was about 20%. The luminescence mechanism of Ln-doped NLBO (Tb³⁺ and Eu³⁺) was analyzed. The relative high quenching concentration was also discussed.     

HPC/H2O/H3PO4 tertiary system: a rheological study

This study characterizes the rheological behavior of the HPC/H₂O/H₃PO₄ tertiary system based on the 3-D phase diagram that was obtained in our earlier work. The effects of frequency, temperature, HPC concentration, liquid composition (H₂O/H₃PO₄ ratio), and phase status on the rheological parameters were thoroughly investigated. The most useful parameter for distinguishing the isotropic (I) and liquid crystalline (LC) phases was tanδ. Agglomeration in the cloudy suspension (CS) phase at high temperature was too severe to allow a smooth flow, so the tanδ and η* represented significant damping, which is a good indicator of the presence of the CS phase. With an increase in temperature, the viscosity of the flow with a single homogeneous phase—either the I phase or the LC phase—or a combination of two homogeneous phases in sequence, obeyed the Arrhenius model. In contrast, once the temperature rose to that of the formation of heterogeneous CS phase, the Arrhenius model was no longer valid. The activation energy E of the I phase was greater, and more sensitive to the HPC concentration, than the LC phase. Finally, the concentration of the sol/gel transition (SGT) declined as temperature increased but increased as the H₃PO₄ content increased. Furthermore, this tertiary system exhibited no clear order of the onsets of the formations of SGT phase, the LC phase, and the CS phase as HPC concentration was varied.