Pt/Cu(001)-p(2×2)-O表面吸附结构的总能计算

采用密度泛函理论(DFT)研究了氧吸附后Pt/Cu(001)表面合金的原子结构和表面性质.计算结果表明,在Pt/Cu(001)-p(2×2)-O表面最稳定结构中,衬底表面原子层不发生再构,氧原子吸附于4重对称的Pt原子谷位,每个氧原子吸附能约为2.303 eV.吸附结构的Cu-O和Pt-O键键长分别为0.202和0.298 nm,氧原子的吸附高度Zcu-O约为0.092 nm.吸附前后Pt/Cu(001)-1ML(monolayer)表面合金的表面功函数分别为4.678和5.355 ev.吸附表面氧原子和衬底的结合主要来自氧原子2p轨道和衬底金属原子d轨道的杂化作用,氧原子吸附形成的表面电子态主要位于费米能级以下约-2.7 eV处.     

两种3D微孔Zn-MOF对水溶液中Fe3+、Cr2O72-和丙酮分子的荧光传感(英文)

通过溶剂热法合成了2种三维微孔锌金属有机框架材料,其分子式为[Zn₃(DBA)(OH)(1,10-phen)₂]_n (1)和{[Zn₂(HDBA)(4,4′-bipy)_1.5]·H₂O}_n (2)(H₅DBA=3,5-二(2′,4′-对羧基苯基)苯甲酸;1,10-phen=1,10-菲咯啉;4,4′-bipy=4,4′-联吡啶)。结构分析表明,配合物1为三核锌基金属单元的三维微孔骨架,配合物2为双核锌基的微孔结构。与2相比,配合物1在水中具有较强的发光性能,可作为检测Fe³⁺、Cr₂O₇^2-和丙酮分子的发光传感器,具有较高的选择性和灵敏度。     

A Luminescent Zn(Ⅱ) Supramolecular Coordination Polymer Constructed from 3,4-Thiophenedicarboxylic Acid and Flexible Benzimidazole-based Connector

A new luminescent coordination polymer [Zn(tdc)(pbim)]n 1(tdc = 3,4-thiophenedicarboxylate, pbim = 1,3-bis(benzimidazol-1ˊ-yl)propane) has been synthesized under hydrothermal conditions. The compound crystallizes in monoclinic system, space group P21/c with a = 8.4840(9), b = 16.4913(17), c = 14.9234(16) A, β = 95.8870(10)°, V = 2077.0(4) A3, Z = 4, Mr = 511.84, Dc = 1.637 Mg/m3, μ = 1.324 mm-1, F(000) = 1048, the final R = 0.0361 and w R = 0.0824 for 3656 observed reflections with I 2(I). Structural analyses reveal that 1 exhibits a onedimensional(1D) double chain, which is further connected into a two-dimensional(2D) supramolecular architecture by π-π stacking interactions. The results indicate that H2 tdc and pbim ligand are effective building blocks in constructing polymers with diverse architecture. Solid state properties for 1, such as infrared spectroscopy, elemental analyses, thermal stability and luminescent property, have also been investigated.     

水热合成法制备CaTiO3:Re3+(Re=Eu,Dy)及发光性能

采用水热合成法合成了CaTiO₃：Re³⁺（Re=Eu,Dy）荧光粉,通过XRD（X-ray diffraction）、SEM（Scanning electron microscope）和光谱对样品进行了分析。研究发现在pH=12时,合成出的CaTiO₃：Re荧光粉结晶度和发光性能最好;SEM分析表明荧光粉颗粒尺寸在450 nm左右,分散性好;确定了稀土离子最佳浓度。在353 nm激发下,CaTiO₃：0.12Dy³⁺的发射峰分别位于485 nm（蓝）和576 nm（黄）。当Dy³⁺浓度发生变化时,两种跃迁产生的蓝黄光发射峰的强度比值（I_Y/I_B）也会发生变化,因此,可以利用这一点对CaTiO₃：Dy³⁺荧光材料的发光颜色进行调谐。     

吸热型碳氢燃料RP-3仿JP-7临界性质(tc、Pc)的测定

建立了一套低停留时间流动法测定物质临界性质的实验装置,样品在加热区停留10s~50s,有效的抑制了被测流体的热分解和热聚合反应。采用正戊烷、正己烷及环己烷为标准物对装置进行了可靠性校验,测定了RP-3和仿JP-7两种吸热燃料的临界温度和压力。同时选用了四种以体积平均沸点和相对密度为主要参数的估算方法,对燃料的临界性质进行了估算,比较了实验值与估算值的偏差,表明API(American Petroleum Institute) 方法 和 Riazi Daubert关联式相对较准确。     

Design and test of frequency tuner for a CAEP high power THz free-electron laser

Peking University is developing a 1.3 GHz superconducting accelerating section highpower THz freeelectron laser for the China Academy of Engineering Physics(CAEP). A compact fast/slow tuner has been developed by the Institute of High Energy Physics(IHEP) for the accelerating section to control Lorentz detuning, compensate for beam loading effect, microphonics and liquid helium pressure fluctuations. The tuner design, warm test and cold test of the first prototype are presented, which has a guiding significance for the manufacture of the formal tuner and cryomodule assembly.     

Comparison of soxhlet, ultrasound-assisted and pressurized liquid extraction of terpenes, fatty acids and Vitamin E from Piper gaudichaudianum Kunth

This paper describes a comparative study of extraction methods of terpenes (terpenic alcohols and phytosterols), fatty acids and Vitamin E from leaves of Piper gaudichaudianum Kunth. The analysis of extracts was done by gas chromatography with mass spectrometric detection. The identification and quantification was made by co-injections of the extract with certified standards. The use of pressurized liquid extraction (PLE; Dionex trade name: ASE, for accelerated solvent extraction) decrease significantly the total time of extraction, the amount of solvent and the manipulation of sample and solvents in comparison with soxhlet (SE) and ultrasound-assisted (USE). In addition, PLE was more effective for the extractions of terpenes (terpenic alcohols and phytosterols), fatty acids and Vitamin E.     

胡萝卜基多孔炭的制备及其电化学电容行为

以冷冻干燥获得的多孔胡萝卜为炭源,经过600℃氮气氛围下炭化和KOH活化,获得了多孔结构的炭材料。采用红外光谱、X-射线粉末衍射、扫描电镜、透射电镜、循环伏安、恒流充放电和交流阻抗对多孔炭进行了微结构和电容性能研究。结果表明:通过活化处理,多孔炭的比表面积从7m²·g^-1大幅提高到147m²·g^-1。而且,活化后的多孔炭产生了414F·g^-1的最大比电容,且电流增至4A·g^-1时的电容保持率为74.5%。而未活化的多孔炭最大电容为253F·g^-1,电容保持率仅为45.1%。此外,活化后的多孔炭还具有优异的电化学稳定性。在5A·g^-1电流下循环8000圈后,其电容保持率高达94%。活化后的多孔炭在电容性能方面的极大改善与其比表面积的大幅提高及介孔的增多有密切关系。     

有机小分子空穴传输材料取代基效应的理论研究

在B3LYP/6-31G(d)水平下对N,N′-二苯基-N,N′-二(1-萘基)-1,1′-联苯-4,4′-二胺(以下简称NTD)及其衍生物(以下简称NTDs)的中性态和离子态结构进行优化,得到各物质的重组能并进行比较。结果显示,NTD分子的化学修饰对重组能λ变化趋势的影响是电子诱导效应和共轭效应共同作用的结果：(1)吸电子诱导效应会引起NTD分子重组能的升高;多重取代位的吸电子效应对分子重组能影响具有相互抵消的作用,不具有简单加和性;给电子诱导效应会引起NTD分子重组能的降低;(2)o位、m位的正共轭效应使体系重组能剧烈升高,共轭作用在o位、m位取代时占主导作用;p位的正共轭效应使体系重组能降低;(3)大范围的共轭π键可能引起所取代的苯环电子分布发生根本性变化,导致分子构型随之发生剧烈变化,从而重组能急剧升高。     

THE MAXIMAL NUMBER OF I_π-CHARACTERS OVER NORMAL SUBGROUPS

Let G be a π-separable group for a set of primes, let N be a normal subgroup of G, and let θ be an Iπ-character(i.e., irreducible π-partial character) of N. We obtain a necessary and suffcient condition for the number of Iπ-characters of G over θ to take the possible maximum |G : N |π. Some applications are given.