Monolayers of tin

Monolayers of tin can be formed on platinum electrodes in an acid solution of the metal cation if the potential is more anodic than required to produce a multilayer deposit. The spectrum of such a monolayer was observed using Sn activity in solution, and showed the following features [216] ... 

While the first and second generation of coatings contained monolayers of TiN or Tie and multilayers composed of TiN, Ti(C, N), TiC, TiB2, and (Ti, A1)N (together with AI2O3) there is a general trend in research towards multicomponent/multiphase... 

Nyokong T, Bedioui F (2006) Self assembled monolayers and electropolymerized thin films of phthalocyanines as molecular materials for electroanalysis. J Praph Phthal 10 1101-1115 Salomon E, Angot T, Papageorgiou N, Layet JM (2005) Self-assembled monolayer of tin-phthalocyanine on lnSb(0 0 l)-(4 x 2)/c(8 x 2). Surf Sci 596 74—81... 

Rehbinder and co-workers were pioneers in the study of environmental effects on the strength of solids [144], As discussed by Frumkin and others [143-145], the measured hardness of a metal immersed in an electrolyte solution varies with applied potential in the manner of an electrocapillary curve (see Section V-7). A dramatic demonstration of this so-called Rehbinder effect is the easy deformation of single crystals of tin and of zinc if the surface is coated with an oleic acid monolayer [144]. 

Electroless reactions must be autocatalytic. Some metals are autocatalytic, such as iron, in electroless nickel. The initial deposition site on other surfaces serves as a catalyst, usually palladium on noncatalytic metals or a palladium—tin mixture on dielectrics, which is a good hydrogenation catalyst (20,21). The catalyst is quickly covered by a monolayer of electroless metal film which as a fresh, continuously renewed clean metal surface continues to function as a dehydrogenation catalyst. Silver is a borderline material, being so weakly catalytic that only very thin films form unless the surface is repeatedly cataly2ed newly developed baths are truly autocatalytic (22). In contrast, electroless copper is relatively easy to maintain in an active state commercial film thicknesses vary from <0.25 to 35 p.m or more. 

FIG. 26 Cyclic voltammograms of 40 monolayers of Langmuir-Schaefer films of cytochrome P450SCC on indium-tin oxide glass plate (ITO) in 10 mM phosphate buffer at a scan rate of 20 mV/s between 0.4 and —0.4 V vs. Ag/AgCl. LS films on ITO worked as the working electrode, platinum as the counter, and Ag/AgCl as the reference electrode. Cholesterol dissolved in X-triton 100 was added 50 p.1 at a time (1) with cholesterol, (2) 50 p.1 of cholesterol, (3) 100 p.1 cholesterol, and (4) 150 p.1 of cholesterol. 

Nanoparticles of Ti02 are deposited on to a glass support covered with a transparent conducting layer of tin-doped indium oxide (ITO). Each nanoparticle is coated with a monolayer of sensitising dye based on Ru(II). Photoexcitation of the dye results in the injection of an electron into the CB of the semiconductor. 

The surface structure and reactivity of vanadium oxide monolayer catalysts supported on tin oxide were investigated by various physico-chemical characterization techniques. In this study a series of tin oxide supported vanadium oxide catalysts with various vanadia loadings ranging from 0.5 to 6. wt.% have been prepared and were characterized by means of X-ray diffraction, oxygen chemisorption at -78°C, solid state and nuclear magnetic resonance... 

What volume of oxygen gas at STP is equivalent to a monolayer of oxygen ions chemisorbed on 1 g of a lightly sintered compact of 200 nm diameter tin oxide particles [Answer 1 ml]... 

Pitner and Hussey studied the electrochemistry of tin in acidic and basic AICI3/I-ethyl-3-methyl-imidazolium chloride-based ionic liquids by using voltammetry and chronoamperometry at 40 °C [15]. They reported that the Sn(II) reduction process is uncomplicated at a platinum substrate, where in the atidic ionic liquid the reduction wave was observed at +0.46 V on the Pt electrode and the oxidation at +0.56 V. When they used a gold electrode instead of platinum, they observed an underpotential deposition of a tin monolayer and an additional underpotential deposition process that was attributed to the formation of tin-gold alloy at the surface. The deposition of tin on glassy carbon was controlled by nudeation. 

BET. Tins model (33) estimates the coverage corresponding to one monolayer of adsorbate and is used to measure the surface areas of solids ... 

Some interesting examples of epitaxy of metals on silicon are reported by Lander and Morrison (320). They deposited A1 vapor on a Si(lll) surface and found five phases of different composition, each containing a monolayer or less of aluminum. The same authors report that adsorption of indium produces at least eight different structures, in quantities of indium up to a monolayer. And on the same Si(lll) surface, Estrup and Morrison (385) showed that the adsorption of Pb in monolayer amounts or less can produce three different surface structures, and that similar quantities of Sn can produce four. The deposits of tin or lead become epitaxial films of pure metal after only a few layers of deposited material are on the surface. 

The material balance of tin anchoring indicated that under monolayer coverage of platinum by PSC the average value of x, is around 1.5. This fact pointed out that Pt nanoclusters are covered by -SnRs and -SnR2 moieties formed in 1 1 ratio. It has been suggested that all anchored surface organometallic species with general formula of -SnR(4.x) and x> 1 can be considered as Coordinatively Unsaturated Primary Surface Complex (CUPSC). 

Sn-Pt/Si02 catalysts below monolayer coverage show only a slight increase in the selectivity of unsaturated alcohol, however the activity of these catalysts is much higher than that of the parent Pt/Si02 catalyst. These results already show the positive effect of tin in carbonyl activation. However, due to the relatively low tin content of these catalysts, the adsorption of the substrate molecule by its olefinic double bond is still possible, consequently the formation of butiral-dehyde is very pronounced. 

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