Lead on silver

UPD can be considered to be adsorption of metal ions B on the surface of a substrate metal A. In this chapter the UPD of lead on Ag(l 11) and Ag (1(X)) will be described.  

The diagram on the (111) surface is characteristic for the process. Three characteristic peaks are observed prior to the bulk deposition of Pb and explained in the following maimer. In peak Aj adsorption of lead on steps and on similar irregularities of the surface is observed because these positions provide a stronger bonding than positions on the flat surface. In A2 adsorption of lead on the terraces of the stepped crystal surface is observed to cover most of the silver surface. It was found that at this potential no adsorption is 

The value of the electrosorption valency determined is zy = 2. The same value was found for Pb on Ag(lOO). 

The structure of lead UPD films on silver (hkl) faces is a consequence of the significant lattice misfit. The atomic radius of Ag is 0.144 nm, the radius of lead 0.174. This prevents a complete epitaxial structure. One can expect that the forced layer structure has a high internal strain. The elastic strain in the film can be estimated from the deviation of the distance of the atoms in the film d from the distance dg in the bulk crystal. The elastic strain is given by the equation 

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Melroy O R, Toney M F, Borges G L, Samant M G, Kortright J B, Ross P N and Blum L 1989 An In situ grazing incidence x-ray scattering study of the initial stages of electrochemical growth of lead on silver(111) J. Electroanal. Chem. 258 403-14... 

Figure 2. Voltammograms for the underpotential deposition of lead on silver single crystal surfaces.

Mao, B.W. and Fleischmann, M. (1988) In-situ X-ray diffraction investigations of the UPD of thallium and lead on silver and gold electrodes. Journal of Electroanalytical Chemistry, 7A1, 297. 

Hydrochloric acid is a strong monobasic acid, dissolving metals to form salt and evolving hydrogen. The reaction may be slow if the chloride formed is insoluble (for example lead and silver are attacked very slowly). The rate of attack on a metal also depends on concentration thus aluminium is attacked most rapidly by 9 M hydrochloric acid, while with other metals such as zinc or iron, more dilute acid is best. 

Many other metal thiosulfates, eg, magnesium thiosulfate [10124-53-5] and its hexahydrate [13446-30-5] have been prepared on a laboratory scale, but with the exception of the calcium, barium [35112-53-9] and lead compounds, these are of Httle commercial or technical interest. Although thaHous [13453-46-8] silver, lead, and barium thiosulfates are only slightly soluble, other metal thiosulfates are usually soluble in water. The lead and silver salts are anhydrous the others usually form more than one hydrate. Aqueous solutions are stable at low temperatures and in the absence of air. The chemical properties are those of thiosulfates and the respective cation. 

Nickel on nickel Gold on gold Platinum on platinum Copper on copper Indium on indium Lead on lead Aluminium on aluminium Silver on silver Iron on iron Tin on tin Steel on tin alloy Steel on steel Steel on Pb alloy Steel on Al. bronze Steel on cast iron Steel on brass Steel on bronze Steel on Pb. brass... 

Another technique that has proved useful in establishing chemical bonding of coupling agents at interfaces is inelastic electron tunneling spectroscopy (ITES). For example. Van Velzen [16] examined 3-(trimethoxysilyl)propanethiol by this technique. Approximately monolayer quantities of this silane were adsorbed on the barrier oxide of an aluminum-aluminum oxide-metal tunneling junction two metals were investigated, lead and silver. It was concluded that the silane is... 

Metal considered platinum, rhodium, silver aluminium bronzes, tin bronzes, gunmetals brasses, nickel silvers Nickel Lead, On and soft solders and cast iron... 

The formation of a PbO coating on Pb when it is anodically polarised in Cl is achieved more readily by alloying lead with silver or other metals, or by incorporating inert conducting microelectrodes in the Pb surface. 

Melroy and co-workers88 recently reported on the EXAFS spectrum of Pb underpotentially deposited on silver (111). In this case, no Pb/Ag scattering was observed and this was ascribed to the large Debye-Waller factor for the lead as well as to the presence of an incommensurate layer. However, data analysis as well as comparison of the edge region of spectra for the underpotentially deposited lead, lead foil, lead acetate, and lead oxide indicated the presence of oxygen from either water or acetate (from electrolyte) as a backscatterer. 

For the case of surface truncation rods, the technique is based on the detection of diffraction peaks between Bragg peaks. Although this requires careful alignment and some a priori knowledge of the structure, monolayer sensitivity can be achieved. In fact, Samant et a/.138 have recently performed an in situ surface diffraction study of lead underpotentially deposited on silver employing this technique along with grazing incidence diffraction. It is clear that this technique will also find widespread use in the near future. 

Similar in properties to lead or silver azide, it explodes on heating or impact. 

Stranski-Krastanov growth has been documented for copper on Au(lll) [101, 102], Pt(100) and Pt(lll) [103], for silver on Au(lll) [104, 105], for cadmium on Cu(lll) [106] and for lead on Ag(100) and Ag(lll) [107-109]. In all of these examples, an active metal is deposited onto a low-index plane of a more noble metal. Since the substrate does not undergo electrochemical transformations at the deposition potential, a reproducible surface can be presented to the solution. At the same time, the substrate metal must be carefully prepared and characterized so that the nucleation and growth mechanisms can be clearly identified, and information can be obtained by variation of the density of surface features, including steps, defects and dislocations. 

Figure 20.6 shows the effect of CuS04 on silver and lead oxide results. 

Figure 20.7 Effect of conditioning time with Na2S on lead and silver recoveries.

Lead Underpotential Deposition on Silver Single Crystals... 

In order to gain more insight into the dependence of the UPD process and structure of the layer on the crystal structure of the substrate, the UPD of lead has been studied on silver crystal surfaces using linear sweep voltammetry. Low energy electron diffraction (LEED) has been used to examine the initial substrate surface as well as the UPD layers as a function of the potential... 

The authors acknowledge very helpful discussions with Dr. R. Adzic of the Institute of Electrochemistry, Belgrade, concerning the underpotential deposition of lead on single crystal silver substrates after chemical polishing. The authors also acknowledge support of the research by the U.S. Office of Naval Research. 

Effect of Underpotentially Deposited Lead on the Surface-Enhanced Raman Scattering of Interfacial Water at Silver Electrode Surfaces... 

The actual isolation of zinc metal on an appreciable scale seems to have occurred first in China in the 10th Century AD (Xu, 1990), using an upwards distillation procedure from secondary (oxidized) zinc minerals. Earlier finds of metallic zinc (such as that at the Agora, noted above) are possibly explained by the chance condensation of small quantities of zinc in the furnace during the production of lead and silver from mixed ores. Much attention has been focused in recent years on northern India, particularly the Zawar region,... 

A commonly used staining method for the cell nucleolus is based on silver nanoparticles [54], The proteins of the nucleolus, such as nucleolin, are known to have high affinity to silver ions due to their amino-terminal domain. Subsequent reduction leads to the formation of the silver nanoparticles stain. In spite of all the efforts, a general and definitive conclusion regarding the attraction between silver... 

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