金(Ⅲ)与某些中性氧配体(RnXO)形成的配合物及其表征

合成了金(Ⅲ)与七种中性氧配体RnXO(R=辛基或苯基;X=N,P,As和S;n=2,3)形成的十种配合物,可概括为两种类型:H(RnXO)x·AuCl_4·Sy(RnXO=TONO、TOPO、TPPO、DOSO、DPSO、TPAsO和bipyO_2;S=乙醇或水;x=1,2,3,y=0,1,2或3)和[Au(L)X_2](L=bipyO_2;X=Cl或Br)。用元素分析、摩尔电导、紫外和红外光谱、核磁共振和热重分析等方法测定了它们的组成和性质,并对其可能的结构也进行了讨论。     

Enhancement of the static SIMS secondary ion yields of lipid moieties by ultrathin gold coating of aged oil paint surfaces

Static secondary ion mass spectrometry (SIMS) is a powerful technique for identification and localization of pigments and binding media present in traditional paintings. Coating the surface of a cross‐section with a 20 Å thick gold layer improves the yields of secondary ions from the fatty acids and diacids. A chalk tablet containing 1% stearic acid, which was partially covered during gold deposition, is used as a test system to investigate the increase of the organic secondary ion yields upon gold deposition in SIMS imaging. A comparative study of a native and gold‐coated aged surface of a lead white‐containing linseed oil paint demonstrates the enhancement of the organic ion yields on a sample relevant for painting studies. The yields of oil paint‐derived negative ions increase by a factor of 3 whereas the yields of positive ions increase by a factor of 2–4. The different types of charged functional groups determine the degree of improvement in yield. Gold coating improves the ionization process of the fatty acids and does not influence their fragmentation. The dissociation of the lead white by the primary ion beam is reduced due to the gold coating. Copyright © 2004 John Wiley & Sons, Ltd.     

Characteristics of Subtractive Anodic Stripping Voltammetry of Lead,Cadmium and Thallium at Silver‐Gold Alloy Electrodes

Silver‐gold alloy electrodes have been studied for the purpose of the quantitative determination of heavy metals by subtractive anodic stripping voltammetry, (SASV). The results have been compared with those obtained with the silver and gold electrodes. The 50/50 a/o Ag/Au alloy electrode is the most suitable for quantifying thallium in the presence of lead and cadmium. The separation of its peak from those of lead and cadmium is 200 mV, which is about twice the separation obtained on the pure metal electrodes and is also better than on mercury. The silver electrode is suitable for the simultaneous determination of thallium, lead and cadmium. The peaks of lead and cadmium overlap on the 50/50 alloy. Pure silver or pure gold can be used for simultaneous quantification of these two metals. The use of gold for quantifying lead and cadmium is more limited because the peak potential of cadmium is shifted in the negative direction as its concentration increases and at [Cd²⁺]>200 nM, the two peaks merge. SASV enables correction for background currents and is of utmost importance for obtaining well‐defined peaks. The peaks of lead, cadmium and thallium appear over a relatively narrow potential range (ca. 200 mV) on all the electrodes presented in this work. For this reason, the quantifying of a peak is based on the derivative at the inflection point of only one of its branches (ascending or descending). All SASV measurements were carried out without removal of oxygen.     

Theoretical study of the electronic spectrum of binuclear gold(I) complexes

The electronic structure and the spectroscopic properties of [Au₂(CS₃)₂]^?2, [Au₂(pym‐2‐S)₂] (pym = pyrimidethiolate), [Au₂(dpm)₂]⁺² (dpm = bis(diphosphino)methane) were studied using density functional theory (DFT) at the B3LYP level. The absorption spectrum of these binuclear gold(I) complexes was calculated by single excitation time‐dependent (TD) method. All complexes showed a ¹(5dσ* → 6pσ) transition associated with a metal–metal charge transfer, which is strongly interrelated with the gold–gold distance. Furthermore, we have calculated the frequency of the gold–gold vibration (ν_Au2) on the above complexes. The values obtained are theoretically in agreement with experimental range. © 2005 Wiley Periodicals, Inc. Int J Quantum Chem, 2005     

Influence of promoters on the performance of Au/MnOx and Pt/SnOx/SiO2 low-temperature CO oxidation catalysts

The influence of promoters on Pt/SnO_x/SiO₂ and Au/MnO_x low-temperature CO oxidation catalysts has been investigated under stoichiometric reaction conditions with no CO₂ added to the feed gas. The performance of Pt/SnO_x/SiO₂ catalysts is improved significantly by the addition of 1 wt.% Fe but reduced by the addition of 5 wt.%Fe, 1 wt.% Sb, 5 wt.% Sb, 1 wt.% As, 5 wt.%As and 1.8 wt.% P. The performance of Au/MnO_x is improved significantly by the addition of 1 at.% Ce but reduced by the addition of 1 at.% Co. For the catalysts and conditions examined, the Au/MnO_x catalysts are superior to the Pt/SnO_x/SiO₂ catalysts with respect to both activity and decay characteristics.     

A Self‐Sampling‐and‐Flow Biosensor for Continuous Monitoring

A self‐sampling‐and‐flow biosensor was fabricated by sandwiching a nitrocellulose strip on the working electrode side of the double‐sided microporous gold electrodes and a wicking pad on the counter electrode side. The double‐sided microporous electrodes were formed by plasma sputtering of gold on a porous nylon substrate. Sample was taken up to the enzyme‐immobilized working electrode by the capillary action of the front nitrocellulose strip dipped into the sample solution, analyzed electrochemically at the enzyme‐immobilized electrode, and diffuses out to the backside wicking pad through the micropores of the electrodes, constituting a complete flow cell device with no mechanical liquid‐transporting device. Biosensor was formed by co‐immobilizing the glucose oxidase and electron transfer mediator (ferrocene acetic acid) on the thioctic acid self‐assembled monolayer‐modified working electrode. A typical response time of the biosensor was about 5 min with the sensitivity of 2.98 nA/mM glucose, providing linear response up to 22.5 mM. To demonstrate the use of self‐sampling‐and‐flow biosensor, the consumption rate of glucose in the presence of yeast was monitored for five days.     

Effect of the Electrode Potential on the Oxygen Reaction Rate in the Electrode System O2, Au/La0.88Sr0.12Ga0.82Mg0.18O2.85

The polarization dependences of a porous gold electrode in contact with a solid electrolyte of the composition La_0.88Sr_0.12Ga_0.82Mg_0.18O_2.85 are studied at 600–800°C and oxygen pressures of 2 × 10⁻²-1 atm. It is shown that the rate of cathodic reduction of oxygen out of the gas phase depends on the preliminary treatment of the sample. The activation energy is equal to 110–135 kJ mol⁻¹ at a low polarization. After increasing the polarization, the activation energy for the cathodic reduction of oxygen equals 75–85 kJ mol⁻¹ and depends on the oxygen pressure as a power function with a power index of 1/4. The rate of the anodic evolution of oxygen is dependent neither on the preliminary treatment of the sample nor on the oxygen pressure in the gas phase and the polarization curve has a characteristic segment, which corresponds to a limiting overvoltage.__________Translated from Elektrokhimiya, Vol. 41, No. 8, 2005, pp. 954–962.Original Russian Text Copyright © 2005 by Shkerin, Sokolova, Beresnev.     

Electrochemical Behavior and Determination of Uric Acid at Single-Walled Carbon Nanotube Modified Gold Electrodes

The voltammetric behavior of uric acid was studied at a single-walled carbon nanotube (SWNT) modified gold electrode. Uric acid can effectively accumulate at this electrode and produce an anodic peak at about 0.45 V (vs. SCE) in pH 5.0 sodium acetate buffer solutions (HAc-NaAc). The experimental parameters, such as solution pH, accumulation time, and amount of SWNT, were optimized for determination. Under the optimum conditions, the anodic peak current is linear to the uric acid concentration over the range of 1.0×10⁻⁷ M to 2.5×10⁻⁵ M with a correlation coefficient of 0.998. The detection limit was 5.0×10⁻⁸ M for 60 s accumulation. The electrode could be easily regenerated and exhibited good stability. A 5.0×10⁻⁶ M uric acid solution was measured ten times using the same electrode, and the relative standard deviation of the peak current was 1.3%. This method was successfully applied to the determination of uric acid in human urine samples, and the recovery was 97–99%. The feasibility for simultaneous determination of xanthine, ascorbic acid and uric acid was discussed. These species did not interfere with each other in a certain concentration range. The influence of some surfactants on the anodic peak was also examined.     

Grain boundary diffusion coefficients in gold–nickel thin films

Polycrystalline gold–nickel thin films are deposited on silicon (111) wafers by evaporation in a vacuum of 2 × 10^?6 mbar. Concentration profiles of heat‐treated specimens are obtained by Auger electron depth profiling. The heat treatments are carried out in a vacuum furnace of 4 × 10^?6 mbar in the temperature interval 473–773 K. The grain boundary diffusion coefficient is determined, using a modified Wipple model, to be (3 × 10^?4 cm² s^?1) exp (?0.94 eV kT^?1). It is concluded that interdiffusion in the investigated system is characterized by type B kinetics, and that grain boundary diffusion plays a dominant role in the mass transport process of such films. Copyright © 2003 John Wiley & Sons, Ltd.