Copper-gold monolayers

Figure 19. In situ X-ray absorption spectrum for a copper upd monolayer on a gold (111) electrode with the polarization of the X-ray beam being perpendicular (A) or parallel (B) to the electrode surface.

Figure 20. Schematic representation of the structure of a copper upd monolayer on a gold (111) electrode surface. The copper atoms sit at threefold hollow sites on the gold surface and water molecules are bonded to the copper atoms.

A well researched and popular class of monolayers is based on the strong adsorption of thiols (R - SH), disulfides (R - S - S - R) and sulfides (R - S - R) onto metal surfaces. Although thiols, disulfides, and sulfides strongly align with a number of different metals Hke gold, silver, platinum, or copper, gold is usually the substrate of choice because of its inert properties and the formation of a well-defined crystal structure. 

Figure 15. Fluorescence-detected (m situ) x-ray absorption spectrum for an underpotentially deposited (UPD) monolayer of copper on a gold (111) electrode with the plane of polarization of the x-ray beam being perpendicular (A) or parallel (B) to the plane of the electrode. Inset Edge region of the x-ray absorption spectrum for a copper UPD monolayer before (C) and after (D) stripping. (From Abruna, H. D., White, J. H., et al., J. Phys. Chem. 92, 7045 (1988), with permission.)...

Figure 17. Structure of a copper UPD monolayer on a gold(lll) electrode surface with...

Another application of the EA method was to determine the shift in the work function of a metal (and the consequent Schottky barrier shift when used as a contact in diodes) that can be induced by self-assembled monolayers (SAMs) [69,70,146-148]. The metal work function can be controlled by attaching a monolayer of polar molecules to the surface of the metal. Because of the inherent ordering of the monolayers (especially for thiol-based adsorbates on copper gold or silver electrodes), the molecular dipoles are oriented relative to... 

The study of ultraArin polymer layers on metals is relevairt in understairding Are behaviour of polymers on surfaces, as well as in Are areas of adlresion aird corrosion. Gold aird copper surfaces cair be covered wiAr monolayers of polymers by adsorjrtion from solution [227, 228, 229, 230, 231,232, 233, 234 aird 235]. 

All metal surfaces are reactive, including the noble ones. Therefore, under ambient conditions, they all have chemisorbed layers on their surfaces. These vary greatly from metal to metal in thickness, from atomic monolayers, to microns, or more. The oxide layer on gold is very thin, for example, whereas it is quite thick on copper or lead. 

Laibinis PE, Whitesides GM, Allara DL, Tao Y-T, Parikh AN, Nuzzo RG (1991) Comparison of the structures and wetting properties of self-assembled monolayers of n-alkanethiols on the coinage metal surfaces, copper, silver, and gold. J Am Chem Soc 113 7152-7167... 

It was demonstrated that the change in thickness of these layers depends on the physicochemical properties of water in these thin water layers. It is reported that on iron surfaces, the number of adsorbed water layers is about 15 at RH 55% and 90 at 100%. Similar values are obtained for Copper and Zinc however significant differences are reported for Platinum, gold, aluminum and silver. These monolayers have been calculated only in presence of water (without oxygen) where the corrosion process is very slow and, consequently, in conditions far from the reality. 

Colavita PE, Doescher MS, Molliet A, Evans U, Reddic J, Zhou J, Chen D, Miney PG, Myrick ML (2002) Effects of metal coating on self-assembled monolayers on gold. 1. Copper on dodecanethiol and octadecanethiol. Langmuir 18(22) 8503-8509... 

Chemical analysis of solids and solutions indicate that in all cases metallic ruthenium, platinum, and gold are deposited on copper. Ruthenium, deposit is restricted to approximately 0.33 of the copper surface atoms, demonstrating that the redox reaction between Cu and Ru3+ can occur only on some special copper sites [11]. With platinum or gold, for the highest amount of modifier introduced (M"+/Cu(s) > 100), a deposit larger than a monolayer is obtained, indicating that all accessible copper atoms and subsurface copper atoms are involved in the redox reaction [13]. 

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