Reorganization of surfaces

One way in which the adsorption of a chlorine atom could affect more than one adsorption site is if the chlorine is incorporated into the subsurface oxide layer. No direct evidence of chloride accumulation in the catalyst subsurface has been published. However, there is at 373 K an apparent competition between chlorine and oxygen for adsorption sites which, we have argued above, correspond to the formation of the first monolayer of the oxide film. In view of this it would be surprising if chloride accumulation in the subsurface did not occur under practical epoxidation conditions. The net result would be to modify the electronic properties of this semi-conducting layer and hence the adsorptive properties of the surface. The chloride catalysed reorganization of surface silver atoms is perhaps indirect evidence of such an affect. ... 

Finally, the results discussed in Section 2.4.3 on the effects of orientation of surface groups on polymeric substrates should be recalled, namely, that at a given temperature polymer chains may become sufficiently mobile such that any polar surface groups may redistribute into the bulk of the material, and the extent of this effect also depends upon the nature of the liquid adhesive in contact with the surface. This decrease in concentration of polar groups at the interface is mirrored in the subsequently measured joint strengths. It is also possible that reorganization of surface groups may occur in the vacuum chamber of modern surface analytical equipment, especially under the action... 

Hence, pseudosimultaneous spectroscopic and flow-cytometric measurements suggest that actin polymerization may be functionally related to aggregation, possibly by reorganization of adhesive molecules on the cell surface. Simultaneous spectroscopic and fluorometric measurements suggest that the signal Ca may be related to oxidant production and degranulation. 

Enantiomeric discrimination and its relation to film component reorganization upon compression can also be observed in dynamic surface tension hysteresis loops. Figure 26 shows the WjA isotherms generated upon five successive compression/expansion cycles (from II = 0 to lOdyncm-1) of racemic and enantiomeric films containing 17 mole percent palmitic acid. The hysteresis loops, obtained on the apparatus described in Section 2 (p. 63), show that the first compression/expansion cycle of the racemic system is repeated in each successive cycle. Upon expansion of the film from the maximum surface pressure back to Odyncm-1, the racemic film returns to its original state without detectable reorganization of the components. However, the... 

The ion-water interactions are very strong Coulomb forces. As the hydrated ion approaches the solution/metal interface, the ion could be adsorbed on the metal surface. This adsorption may be accompanied by a partial loss of coordination shell water molecules, or the ion could keep its coordination shell upon adsorption. The behavior will be determined by the competition between the ion-water interactions and the ion-metal interactions. In some cases, a partial eharge transfer between the ion and the metal results in a strong bond, and we term this process chemisorption, in contrast to physisorption, which is much weaker and does not result in substantial modification of the ion s electronic structure. In some cases, one of the coordination shell molecules may be an adsorbed water molecule. hi this case, the ion does not lose part of the coordination shell, but some reorganization of the coordination shell molecules may occur in order to satisfy the constraint imposed by the metal surface, especially when it is charged. 

Another test of film stability is shown in Figure 13, where compressed films were expanded and recompressed. The hysteresis pattern was observed for both enantiomer films and racemate films at 15°C but not at25°C(101). This indicates again the relatively high viscosity of surface films and the sensitivity of molegular reorganization to changes in structure and conditions. 

Such control of surface functionahties, surface chemical potential, and surface dipole is not possible in mixed SAMs of cofunctionalized saturated -alkanethiols, since dipolar interaction of surface functionahties wiU result in surface reorganization [95, 99-101]. 

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