The Comparative Study of “Adsorbed Co” Oxidation On the Rough and Smooth Pt Electrodes

Abstract

The oxidation of carbon monoxide adsorption products from rough and smooth platinum electrodes has been studied by cyclic voltammetry. It was found that the roughness of the electrode surface has strong influence on the composition and/or structure of the final adsorption products.     

Chiral Recognition of Penicillamine Enantiomers Based on DNA‐MWNT Complex Modified Electrode

Double‐stranded DNA and multiwalled carbon nanotube (MWNT) complex modified glassy carbon electrodes (DNA‐MWNT‐GCE) were employed to discriminate penicillamine (PA) enantiomers. Cyclic voltammetry, electrochemical impedance spectroscopy, atomic force microscopy and ultraviolet‐visible spectroscopy were used to characterize the enantioselective phenomenon. The results indicated that the binding effect between L ‐PA and DNA‐MWNTs was stronger than that of D ‐PA and DNA‐MWNTs. In addition, the influencing factors of the modified electrodes were systematically investigated. The modified electrodes exhibited a linear response towards PA enantiomers from 1.0×10^?1 to 1.0×10^?8 mol L^?1 and detection limits of 3.1×10^?9 and 3.3×10^?8 mol L^?1 for L ‐PA and D ‐PA, respectively.     

阴离子交换柱分离不同价态砷的研究及其应用

利用醋酸型AG 1-X8阴离子交换树脂和氯化物型AG 1-X8阴离子交换树脂对As(Ⅴ)和As(Ⅲ)吸附的差异,实现As(Ⅲ)和As(Ⅴ)的有效分离。过滤和酸化后的水样流经树脂交换柱(75mm×5.3mm i.d.)时,醋酸型AG 1-X8阴离子交换树脂可吸附As(Ⅴ);而As(Ⅲ)可通过树脂柱。被吸附的As(Ⅴ)用0.12mol/L HCl淋洗出来,在此过程中醋酸型树脂转化为氯化物型树脂。该树脂交换柱可多次循环使用。本方法简单易行,适用于野外现场条件下高砷地下水中As(Ⅲ)和As(Ⅴ)的分离和准确测定;用于检测水铁矿除砷过程中砷价态变化。结果表明,缺氧条件下水铁矿对As(Ⅲ)和As(Ⅴ)的吸附动力学特征遵循假二级反应动力学模式,内扩散不是控制As(Ⅲ)和As(Ⅴ)吸附的因素。随着时间的推移,膜扩散对吸附的控制作用增强。     

Adsorptive Voltammetric Measurement of Trace Level of Iron(III) with 4–(2–Pyridylazo) Resorcin

Abstract

The polarographic behavior of the complex of iron–4– (2–pyridylazo) resorcin(PAR) was studied. In HAc– NaAc– EDTA buffer solution, the complex can be adsorped on a hanging mercury drop electrode giving a sensitive adsorptive complex reduction peak with a peak potential at -0.36V(vs. SCE). Optimum experimental conditions were found by the use of 0.08mol/L HAc, 0.06mol/L NaAc, 5.0 × 10^?3mol/L EDTA and 1.0 × 10^?5mol/L PAR. With preconcentration for 60s, the derivative peak height of the complex compound is linearly proportional to the concentration for Fe in the range from 1.0 × 10^?9mol/L to 1.0 × 10^?7mol/L. For a 2–min pre–concentration time, the detection limit found was 2.0 × 10^?10mol/L. This method has high sensitivity and selectivity. It has been applied to the determination of trace iron in food and water samples without any pre–separation step.     

Jump Condition for Diffusive and Convective Mass Transfer Between a Porous Medium and a Fluid Involving Adsorption and Chemical Reaction

In this paper, mass transfer at the fluid–porous medium boundaries is studied. The problem considers both diffusive and convective transport, along with adsorption and reaction effects in the porous medium. The result is a mass flux jump condition that is expressed in terms of effective transport coefficients. Such coefficients (a total dispersion tensor and effective reaction and adsorption coefficients) may be computed from the solution of the corresponding closure problem here stated and solved as a function of the Péclet number (Pe), the porosity and a local Thiele modulus. For the case of negligible convective transport (i.e., ), the closure problem reduces to the one recently solved by the authors for diffusion and reaction between a fluid and a microporous medium.     

亚甲基蓝在胶体银表面的吸附——表面增强拉曼光谱和密度泛函理论计算

获得了不同浓度下亚甲基蓝(methylene blue,MB)溶液在银溶胶中的表面增强拉曼光谱。结果表明： 亚甲基蓝分子与银纳米粒子高浓度下物理吸附为主,低浓度下化学吸附为主;不同浓度下存在不同的吸附取向,即高浓度下为“直立”取向,低浓度为“平躺”取向。通过观察低浓度下MB在银胶中吸附时间对谱图的影响,得知低浓度下吸附取向不随时间发生变化。应用密度泛函(DFT)方法在B3LYP/6-31+G*和LANL2DZ基组水平上对亚甲基蓝阳离子(MB+)及MB+与Ag原子形成的不同构型体系进行了结构优化和频率计算。实验与理论计算结果表明,MB+有可能通过N—Ag和S—Ag与Ag原子形成两种较强的吸附构型。电荷布居分析表明,与S原子相比,芳香环上的N原子更易与Ag发生相互作用。还对实验观察到的部分谱峰及它们的振动模式作出了初步归属和讨论。     

H2分子在碱金属掺杂碳纳米管上的吸附特性

采用密度泛函理论研究了H₂在碱金属(M=Li, K)掺杂的扶手椅型单壁碳纳米管上的吸附. 对于碱金属管内掺杂, 模拟了4种氢吸附构型; 对于管外掺杂, 考虑了两种吸附结构, 同时还考虑了两种不同的掺杂浓度. 所有吸附模型都进行了全优化. 计算结果表明, 碱金属掺杂后, 碱金属与碳纳米管之间发生电子授受作用使得碱金属带正电荷, 对于金属Li, 管内掺杂更有利于电子向碳纳米管转移; 与管内掺杂相比, Li原子的管外掺杂更有利于H2分子吸附. 碱金属管外掺杂的碳纳米管吸附H₂的最稳定结构, 存在碱金属原子与H₂分子的配位作用.     

多壁碳纳米管表面对硝基苯酚印迹复合材料的制备与吸附性能

以多壁碳纳米管表面接枝的L-苯丙氨酸为结合位点, 甲基丙烯酸为功能单体, 乙二醇二甲基丙烯酸酯为交联剂, 采用沉淀聚合技术, 在碳纳米管表面制备了对硝基苯酚印迹复合材料. 采用红外光谱和扫描电镜研究了该印迹复合材料的结构和形貌, 结果表明, 在碳纳米管表面接枝了一层稳定的印迹材料. 采用高效液相色谱研究了该印迹材料的等温吸附性能, 结果表明, 该印迹材料对模板分子具有较大的吸附容量(Qmax=80.5 μmol/g)和良好的选择吸附性能(选择因子达2.5). 以该印迹材料作为固相萃取吸附剂, 研究了它对对硝基苯酚和其它结构类似物混合溶液的动态吸附性能, 结果表明, 印迹复合材料对对硝基苯酚的吸附容量不受结构类似物浓度的影响, 能较好地应用于对硝基苯酚的分离富集检测.     

Molecular adsorption and growth of n-butane adlayers on Pt(1 1 1)

The molecular adsorption of n-butane and the growth of n-butane adlayers on Pt(1 1 1) was investigated using molecular beam techniques, temperature-programmed desorption (TPD) and low-energy electron diffraction (LEED). It is found that as the surface coverage of n-butane increases, structural changes occur in the adlayer at surface temperatures near 98 K that are accompanied by changes in the binding energy and mobility of the adsorbed species. The film growth process can be divided into four distinct coverage regimes. At low coverages (θ<0.14 ML, where 1 ML is defined as one butane molecule per Pt atom) a disordered monolayer forms in which the butane molecules prefer to lie parallel to the surface in order to minimize their binding energy. At coverages from 0.14 to 0.20 ML, ordered regions develop within the monolayer in which the butane molecules also lie parallel to the surface. The binding energy in the ordered phase is lower than that in the disordered phase due to repulsive intermolecular interactions. A more densely-packed ordered phase begins to form at 98 K after the low-coverage ordered phase saturates at 0.20 ML. The experimental results suggest that the n-butane molecules tilt away from the surface in the high-coverage ordered phase. Finally, a disordered second layer phase forms after the high coverage ordered phase saturates at 0.35 ML. The molecules in the second layer are very mobile at 98 K and rapidly diffuse to the edges of the beam spot. Interchange of molecules between the second layer and ordered monolayer is found to govern the net rate of second layer diffusion at surface temperatures less than 133 K. The adsorption probability of n-butane on Pt(1 1 1) continuously increases with increasing coverage, with no significant dependencies on the structure of the n-butane adlayer. This finding indicates that the long-range arrangements and molecular orientations of a mobile alkane adlayer have a negligible influence on the intrinsic adsorption dynamics, suggesting that the energy transfer processes that facilitate adsorption are highly localized.     

氢气在炭狭缝微孔内吸附的预测

通过边界的平均场近似,推导二平板狭缝孔格子理论Ono-Kondo吸附等温方程。利用格子模型特性和微观物理学理论,计算氢分子在石墨平面的最大吸附容量。比较由氢分子在石墨平面二典型聚集状态标定的Ono-Kondo方程,并用预测精度较高的方程计算了与文献相同条件下的吸附等温线。在比较了计算结果、试验结果和GCMC分子模拟结果后,对Ono-Kondo吸附等温方程的特点、理论基础作了分析,指出了方程的适用范围。