AVS 50th International Symposium
    Surface Science Tuesday Sessions
       Session SS1-TuA

Paper SS1-TuA9
The Surface Chelate Effect

Tuesday, November 4, 2003, 4:40 pm, Room 326

Session: Water at Interfaces II: Adsorbed Layers
Presenter: R. Major, University of Minnesota
Authors: R. Major, University of Minnesota
X.-Y. Zhu, University of Minnesota
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The adsorption of metal ions from a liquid phase to a molecularly functionalized solid surface is important in many disciplines, such as chemical sensing, environmental cleanup, protein purification, and "molecular beaker epitaxy". Few studies have investigated the kinetics and thermodynamics in adsorption at a such a liquid-solid interface. One distinguishing factor related to the coordination of metal ions to surfaces is that the surface functional groups can be arranged in a two-dimensional array. We set out to explore how this two-dimensional arrangement may lead to an inherent chelate effect, using the model system of Cu2+ ions adsorption on self-assembled monolayers of 16-mercaptohexadecanoic acid (MHA) on Au. The formation constant of Cu2+ with the MHA surface was found to be two orders of magnitude greater than Cu2+ with succinic acid or glutaric acid in aqueous solutions. Both of these molecules are known to chelate to metal ions forming 7 and 8-membered rings. The greater surface chelate effect is attributed to the presence of the two-dimensional array of ligands on the surface. We believe the surface chelate effect demonstrated here is of general significance to adsorption on functional surfaces and should depend strongly on chemical functionality and monolayer structure.