COLL 286 |
| Temperature programmed desorption (TPD) experiments characterize the interaction between water and self assembled monolayers (SAM) of mixed hydrophobic and hydrophilic thiols on Au(111). Two-component SAM surfaces form by exposing gold samples to mixed millimolar solutions of methyl-terminated and carboxylic acid-terminated thiols. Water desorption spectra from the pure hydrophobic surface exhibit first order desorption at low coverage with narrow peaks at ~145 K. Conversely, desorption of water from a pure acid-terminated surface exhibits broad peaks shifted to higher temperatures. Interestingly, water TPD spectra from a 50% / 50% methyl- and acid-terminated surface closely resemble desorption from the purely hydrophobic SAM. Increasing the surface acid fraction beyond 50% shifts desorption profiles to higher temperatures with long, high-temperature tails approaching the behavior of water desorbing from the pure acid-terminated surface. We discuss the implications for water interaction with "textured" organic surfaces as well as with atmospherically-relevant organic aerosol. In particular, results suggest that significant surface oxidation is necessary to impact water interactions with organic aerosol surfaces. |
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The Physical Chemistry of Environmental Interfaces
9:00 AM-1:10 PM, Tuesday, April 8, 2008 Morial Convention Center -- Rm. 225, Oral
Division of Colloid & Surface Chemistry |