ANYL 267 |
| Resonantly-enhanced surface second harmonic generation (SHG) measurements carried out at pH 7 and room temperature show how surface-bound carboxylic acid and methyl ester functional groups control the interaction of the EPA priority pollutant chromate with fused silica/water interfaces at environmentally representative Cr(VI) concentrations between 1×10-6 to 2×10-4 M. These functional groups, chosen because of their biogeochemical importance, were anchored to the silica surface using organosilane chemistry to avoid competing complexation processes in aqueous solution and competitive adsorption with Cr(VI), and characterized using broadband vibrational sum frequency generation (BB-VSFG) and SHG. In contrast to non-functionalized silica/water interfaces, Cr(VI) binding to the functionalized silica/water interfaces results in S-shaped adsorption isotherms that are modeled using stabilizing lateral adsorbate-adsorbate interactions among the surface-bound Cr(VI) species. These results show, for the first time, that cooperativity and hydrogen-bonding decrease Cr(VI) mobility substantially when carboxylic acid functional groups are present at the silica/water interface. |
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Analytical and Biological Applications of Non-linear Optics
8:30 AM-12:10 PM, Monday, 29 August 2005 Washington DC Convention Center -- 155, Oral
Division of Analytical Chemistry |