COLL 477 |
| Joel M. Harris and Vanessa B. Oklejas. Department of Chemistry, University of Utah, 315 South 1400 East, Salt Lake City, UT 84112-0850 |
| High-sensitivity SERS monitoring is being applied to study the perturbation of chemically-modified metal surfaces by electric fields. To measure electric fields available for perturbation, we have utilized Stark tuning of a CN stretching frequency from a terminal nitrile group incorporated into mixed self-assembled monolayers. The potential-dependent reactivity of 8-hydroxyquinoline, immobilized at an electrode surface, toward metal-ion complexation is also investigated. At low concentrations of metal ions, we observe reversible potential control over the ligand metal-ion binding. Positive surface potentials favor binding of metal cations which is inconsistent with the Poisson-Boltzmann influence on metal-ion activity in the double layer. The spectroscopic data, however, also show modulation of the hydrazone-to-azo tautomerism of the ligand being influenced by electric field. Electronic structure calculations of the dipole moments of the two tautomers predict that a positive electric field at the metal surface favors the reactive (azo-quinoline) form of the ligand. The switching of the ligand is consistent with interfacial fields measured by the vibrational Stark effect. The results illustrate that ligand reactivity toward metal-ion binding may be controlled an electric field that exerts direct control over its structure. |
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Vibrational Analyses of Dry and Wet Surfaces
8:30 AM-11:30 AM, Thursday, April 1, 2004 Marriott -- Grand Ballroom H, Oral
Division of Colloid and Surface Chemistry |