Evolution of Gold Species in an Au/CeO2 Catalyst and Its Impact on Activity for CO Oxidation

An Au/ceria(0.44%, mass fraction) catalyst containing gold ions was prepared by a modified deposition precipitation method, and the evolution of gold ions in the catalyst and its influence on the catalysis of CO oxidation were investigated. It was found that the as-prepared catalyst containing gold ions with high valence could fully oxidize CO at –10 °C initially but was deactivated gradually at low temperatures during the reaction with CO or treatment by unpurified air. The deactivation of the catalyst during CO oxidation or treatment of it by unpurified air was independent and progressive at low temperatures while the activity of the catalyst at relatively high temperatures was maintained well. During the reaction with CO or treatment by unpurified air, the XPS results indicate that gold species evolved from high valence to low valence and the diffuse reflectance UV-Vis spectra show that high valence gold was reduced to charged gold clusters, gold clusters grew to small gold crystals and small gold crystals grew to large gold particles. Accordingly, the high valence gold corresponded to the activity at low temperatures and the metallic gold was active and relatively stable at high temperatures. The turnover frequencies(TOF) of the catalysts treated by different methods at 273 K decreased with the evolution of gold species from high valence to low valence, no maximum of TOF was observed although gold particles in the catalyst attained to about 2―3 nm during the treatment. An Au/ceria catalyst with a gold load of 0.87% (mass fraction) maintained a good activity for CO oxidation within 18 h at room temperature. The catalysts were characterized via transmitted electronic microscopy(TEM), inductively coupled plasma optical emission spectrometry(ICP-OES), X-ray diffraction(XRD) and BET specific surface area and UV-Vis DRS as well.     

超细红色荧光粉LaMgAl_(11)O_(19):Eu~(3+)的制备与发光性能

采用凝胶-燃烧法制备了稀土Eu3+掺杂的LaMgAl11O19红色荧光粉的前驱粉末,在低于700℃退火处理时,得到非晶态样品,而高于850℃退火处理后为单一六方相结构LaMgAl11O19:Eu3+样品.SEM结果表明,该法制备的样品为颗粒分布均匀,粒径在200～400nm之间的超细粉末.通过激发光谱和发射光谱研究了Eu3+在LaMgAl11O19基质中的发光性能,结果显示,非晶态和晶态La1-xMgAl11O19:xEu3+样品都可发光,在613nm波长光的监测下所得荧光粉的激发光谱为一宽带和系列锐峰,其最强激发峰出现在蓝光465nm处,次强峰为394nm,表明该荧光粉与广泛使用的紫外和蓝光LED芯片的输出波长相匹配.在465nm波长光的激发下观察到超细LaMgAl11O19粉末中Eu3+的613nm(5D0→7F2)强的特征发射,且随着粉末逐渐成相5D0→7F2跃迁明显增强,说明LaMgAl11O19:Eu3+超细粉末可作为白光LED的红色补偿荧光粉.     

Synthesis and Characterizations of Ferrocenyl Carbonyl Chromium and Cobalt Clusters

Two novel bimetallic complexes, [Cr(CO)₃(η ⁶-C₆H₅)–C≡C–C₆H₄–Fc] (Fc = C₅H₅FeC₅H₄] (1) and [Cr(CO)₃(η ⁶-C₆H₅)–C ≡ C–Fc–C(CH₃)₂–Fc] (3), were synthesized by the Sonogashira coupling reaction. By using of (1) and (3) as ligands to react with Co₂(CO)₈, two others novel polymetallic complexes, [Cr(CO)₃(η ⁶-C₆H₅){Co₂(CO)₆-η ²-μ ²-C≡C–}–C₆H₄–Fc] (2) and [Cr(CO)₃(η ⁶-C₆H₅){Co₂(CO)₆-η ²-μ ²-C≡C–}Fc–C(CH₃)₂–Fc] (4) were obtained. Four carbonyl complexes were characterized by elemental analysis, FT-IR, NMR and MS. The molecular structures of complexes (1), (2) and (4) were determined by single crystal X-ray diffraction. The interactions among the ferrocenyl, Cr(CO)₃ and Co₂(CO)₆-η ²-μ ²-C≡C– units were investigated by cyclic voltammetry.     

Pd/SAPO-34催化剂上CO低温氧化反应

 采用水热法合成了小晶粒的 SAPO-34, MnSAPO-34 和 CuSAPO-34 分子筛, 并以它们为载体采用浸渍法制备了一系列不同 Pd 含量的催化剂用于催化 CO 氧化反应. 结果表明: 分子筛载体、催化剂制备条件、反应条件、Pd 含量及预还原等对催化剂的活性影响较大. 催化剂活性随焙烧温度的增加而降低, 而随着反应温度的升高而提高, 担载在 SAPO-34 上 Pd 含量为 1.35% 时性能最佳. X射线衍射和透射电镜结果表明 Pd 物种高度分散于催化剂上, 粒子粒径在 2~8 nm; X射线光电子能谱及氢气程序升温还原结果表明, 高度分散的 Pd2+ 物种是 CO 氧化反应活性位. 随着反应进行被还原为 Pd0 物种, 因而导致催化剂活性下降. H2 预还原处理催化剂致使活性下降的实验结果也支持了这一结论.     

甲酚红褪色分光光度法测定吡罗昔康

用褪色分光光度法(测定药物制剂和生物样品中吡罗昔康含量。)在pH8.75的tris-HCl缓冲溶液中,甲酚红与吡罗昔康反应形成离子缔合物,使甲酚红溶液褪色,最大褪色波长位于570nm,吡罗昔康浓度在0.06628～11.60μg/mL范围内遵循比尔定律,回归方程为ΔA=0.1404c+0.0067,相关系数为r=0.9996,表观摩尔吸光系数为4.703×104L·mol-1.cm-1。据此建立了方法,样品测定平均回收率为97.51%～101.4%。     

基于MATLAB软件对不同偏振光在不同介质中的传播过程的动态模拟

利用MATLAB软件对不同偏振光在真空、各向同性介质、线型各向异性介质以及圆型各向异性介质中的传播过程进行了三维动态模拟,能够加深学生对光的偏振概念以及各种偏振光与不同介质之间相互作用原理的理解。     

量子棒中强耦合杂质束缚极化子的振动频率

给出了具有椭球边界量子棒经坐标变换成球形边界的哈密顿量。采用线性组合算符和幺正变换的方法研究了在非均匀抛物限制势下量子棒中强耦合杂质束缚极化子的性质。导出了量子棒中强耦合杂质束缚极化子的振动频率和声子平均数随库仑束缚势、电子-声子耦合强度、椭球的纵横比和量子棒的横向和纵向有效受限长度的变化关系。数值计算结果表明:振动频率和声子平均数随电子-声子耦合强度和库仑束缚势的增强而增加,随量子棒的横向和纵向有效受限长度和椭球的纵横比的减小而增大。表现出量子棒的奇特的量子尺寸限制效应。     

卤代苯甲酸-TPTZ铽配合物的合成、表征及荧光性能

分别以对溴苯甲酸和对碘苯甲酸为第一配体,2,4,6.三吡啶基三嗪(TPTZ)为第二配体,以铽为中心,La3+、Y3+、Cd3+为掺杂离子,合成了8种铽及其掺杂配合物,对其进行了C、H、N元素分析及稀土络合滴定、紫外光谱、红外光谱和荧光光谱测定.推测配合物的组成为:Tb(P-BrBA)3(TPTZ)·2H2O和Tb(P-...     

基于LabVIEW的激光发散角测试软件开发

根据可变光阑法测量发散角的原理,利用具有强大数值计算与串口通信能力的LabVIEW语言搭建发散角测试软件平台.平台测试结果表明,测试软件具有较好的显示功能与可操作性,同时具有参数设置灵活、可二次开发等优点.在总程序设计的基础上,分别介绍了数据采集、数据处理及数据存储的三个程序模块,最后提出用LabVIEW的循环、嵌套等...     

Magnetic and transport properties of bilayered manganites La1.2Sr1.8Mn2-xGaxO7（x=0,0.08）

The magnetic and electrical properties of nonmagnetic Ga +3 ion substitution for Mn site are investigated in the bilayer manganite La 1.2 Sr 1.8 Mn 2 O 7.When the Mn is substituted by Ga,the ferromagnetic property obviously weakens,the magnetic transition temperature decreases and a spin-glass behaviour occurs at low temperature.Meanwhile,doping causes the resistivity to dramatically increase,the metal-insulator transition temperature to disappear,and a greater magneto-resistance effect to occur at low temperature.These effects result from the fact that Ga substitution dilutes the magnetic active Mn-O-Mn network and weakens the double exchange interaction,and further suppresses ferromagnetic ordering and metallic conduction.