Substoichiometric Determation of Silver Traces in Palladium with Adsorptive Sampling

A substoichiometic analytical method of high sensitivity combined with adsorptive sampling has been worked out for the determination of traces of silver in palladium making use of the selective deposition of microquantities of silver from aqueous solutions of palladium salts on cathodically polarized platioum surfaces. The stability and reporducibility of the saturation values of deposited silver are practially independent of the content and concentration of silver and palladium in the solution. The sensitivity proved to be 0.01 ppm, the accuracy ± 30 per cent.     

Untersuchung der spontanen Abscheidung von Silber an pulverförmigem Platin aus salpetersauren Lösungen

Es wurde festgestell, daβ Silberionen an mit wasserstoffgesättigten Platimpulver sich abschieden und die maximal abgeschiedence Menge im Salpeterāure-Konzentrationsbereich 5 n – 0,0001 n die der Monoshcict entsprechende Menge nicht erreicht. Die Meβergebnisse bezüglich der Konzentrationsabhängigkeit der Abscheidung scheinen formell die Langmuirsche Gleichung zu erfūllen, doch zeigen die aus dieser Gleichung berechneten T_σ - Werte eine pH-Abhāngigkeit und stimmen mit der BET-Ober-fläche nicht überein. Die spontne Abscheidung von Silber an Platinpulver kann für die Abtennung von radioaktiven Silber-Isotopen angewandt werden.     

Verteilungskoeffizienten von Ag,In, Re,Au, Hg,Tl, Pb und Bi in Salpetersäure-Methanol-Gemischen

Der Anionenaustausch unter Verwendung von Salpetersäure-Methanol-Gemischen ist in den letzten Jahren von einer Anzahl von Autoren untersucht worden [1, 2, 3, 4]. In einer früheren Arbeit hatten wir bereits auf seine praktisehc Anwendbarkeit für die Trennung der SK hingewiescn [5]. In der vorliegenden Arbeit werden von uns die Verteilungs-koeffizienten von Ag, In, Re, Au, Hg, Tl, Pb und Bi angegeben und Beispiele für mögliche Trennungen angeführt.     

吸附O的Cu(110)c(2×1)表面原子结构和电子态

采用第一性原理的密度泛函理论方法计算了清洁Cu(110)表面和吸附O原子的Cu(110) c(2×1)表面的原子结构, 结构弛豫和电子结构, 得到了各种表面结构参数. 分别计算了O原子在Cu(110)表面三个可能吸附位置吸附后的能量, 并给出了能量最低的吸附位置上各层原子的弛豫特性和态密度. 结果表明O吸附后的Cu(110)表面有附加列(added-row)再构的特性, O原子吸附在最表层铜原子上方, 与衬底Cu原子的垂直距离为0.016 nm, 以氧分子为能量基准的吸附能为－1.94 eV; 同时由于Cu 3d- O 2p态的杂化作用使得低于费米能级5.5~6.0 eV的范围内出现了局域的表面态. 计算得到清洁的和氧吸附的Cu(110)表面的功函数分别为4.51 eV和4.68 eV. 电子态密度的结果表明：在Cu(110) c(2×1) 表面O吸附的结构下, 吸附O原子和金属衬底之间的结合主要是由于最表层Cu原子3d态和O原子2p态的相互作用.     

Dielectric and tunable properties of highly (110)-oriented (Ba<Subscript>0.65</Subscript>Sr<Subscript>0.35</Subscript>)TiO<Subscript>3</Subscript> thin films deposited on Pt/LaNiO<Subscript>3</Subscript>/SiO<Subscript>2</Subscript>/Si substrates

Highly (110)-oriented Ba_0.65Sr_0.35TiO₃ films were deposited on Pt/LaNiO₃/SiO₂/Si substrates by a sol–gel method. It was found that the (110)-preferred Pt film was very effective for growing (110)-oriented ferroelectric films with perovskite structure. The as-grown Ba_0.65Sr_0.35TiO₃ films showed good dielectric properties with dielectric constant and loss tangent tan δ = 0.026. Excellent dielectric tunability was also achieved in the (110)-oriented films. With applying an electric field of 230 kV/cm at 100 kHz, the dielectric tunability and the figure of merit can reach up to 63.4% and 16, respectively. These results indicate that the highly (110)-oriented Ba_0.65Sr_0.35TiO₃ film is a promising candidate for the applications in microwave tunable devices.     

Oxidative cyclization of 2-pyrrolidinyl-acetamide and 2-pyrrolidinyl-propionamide local anaesthetics

2 - Pyrrolidinyl - acetamide and -propionamide local anaesthetics (1a–d) on oxidation with mercuric acetate, potassium hexacyanoferrate(III) and potassium permanganate underwent oxidative cyclization to give new bicyclic compounds, hexahydro - 1H - pyrrolo[1,2 - a]imidazolin - 2 - ones (2a–d). The propionamides (1c–d) yielded mixtures of the two possible diastereoisomers of 2c and 2d. These were separated; in solution and above their melting points they epimerized via ring opening and reclosure between the 7a-carbon and 1-nitrogen atoms.     

Time evolution of adatom and vacancy clusters on Ag(110)

The time evolution of adatom and vacancy islands on an Ag(110) surface is studied by using a variable-temperature ultrahigh vacuum scanning tunneling microscope. The islands are created by Ar⁺ ion sputtering at low temperatures and at very low fluxes (0.004 ML s⁻¹). The area of both kinds of island decreases linearly as a function of time, at least for small islands. The experimental results are compared with kinetic Monte Carlo simulations.     

Fe(110)面上CO化学吸附状态的吸附历史依赖关系

Fe(110)面上直接在室温时吸附的CO同先在170 K吸附然后升温到室温的CO吸附有所不同. 前者有解离而后者无解离; 另外, 前者的饱和吸附量比后者低. 这可以用前者发生了解离来解释. 根据以上结果, 提出了以下的设想, Fe(110)面上的CO解离除了需要足够的热能而外, 还需要在表面的吸附位上有邻近的其它未被覆盖Fe原子的存在, 即需要一定的表面结构.     

Lead underpotential deposition on Au(110)

The electrochemical underpotential deposition (UPD) of lead on Au(110) was investigated by XPS using a custom‐built ultrahigh vacuum apparatus containing a chamber for electrochemical studies. A two‐step deposition process for lead UPD was confirmed. A large increase in the surface concentration of oxygen was found in solutions containing lead. The presence of lead was detected on the gold surface at all potentials within the range investigated (?500 mV to 1500 mV vs. Ag/AgCl). Degradation of chlorine by x‐rays was observed. The change in surface components with potential was investigated and linked to models of UPD and oxidation. The initial random deposition of lead from solution led to surface disordering. Copyright © 2003 John Wiley & Sons, Ltd.     

Adsorption of benzene, fluorobenzene and meta-di-fluorobenzene on Cu(110): a computational study

We modelled the adsorption of benzene, fluorobenzene and meta-di-fluorobenzene on Cu(110) by Density Functional Theory. We found that the adsorption configuration depends on the coverage. At high coverage, benzene assumes a tilted position, while at low coverage a horizontal slightly distorted geometry is favoured. Functionalizing the benzene ring with one or two fluorine atoms weakens the bonding to the surface. A rotation is induced, which decreases the distance of the fluorine atom from the surface. STM simulations reveal that details about both, benzene adsorption geometry and fluorine position, can be only detected at short tip-surface distances.