HR: 0800h
AN: A11A-0845    [Abstracts]
TI: Unusual Aggregates from the Ozone Oxidation of Self-Assembled Monolayers
AU: * McIntire, T M
EM: mcintire@uci.edu
AF: University of California, Department of Chemistry , Irvine, CA 92697-2025 United States
AU: Lea, A
EM: scott.lea@pnl.gov
AF: Pacific Northwest National Laboratory, P.O. Box 999, K8-93, Richland, WA 99352 United States
AU: Gaspar, D J
EM: Daniel.Gaspar@pnl.gov
AF: Pacific Northwest National Laboratory, P.O. Box 999, K8-93, Richland, WA 99352 United States
AU: Jaitly, N
EM: navdeep.jaitly@pnl.gov
AF: Pacific Northwest National Laboratory, P.O. Box 999, K8-93, Richland, WA 99352 United States
AU: Dubowski, Y
EM: yaeld@tx.technion.ac.il
AF: Technion-Israel Institute of Technology, Faculty of Civil and Environmental Engineering, Haifa, 32000 Israel
AU: Li, Q
EM: qiguangl@uci.edu
AF: University of California, Department of Chemistry , Irvine, CA 92697-2025 United States
AU: Finlayson-Pitts, B J
EM: bjfinlay@uci.edu
AF: University of California, Department of Chemistry , Irvine, CA 92697-2025 United States
AB: Airborne particles are important in visibility, climate, human health and atmospheric reactions. Changes in the chemical and physical properties of organics associated with airborne dust particles, which are distributed globally, and which undergo oxidation to polar species during transport, are of considerable interest. In this work we report the first observation of large organic aggregates on surfaces generated by the ozone oxidation of terminal alkene self-assembled monolayers (SAMs) used as proxies for organics on airborne dust particles. SAMs with a terminal alkene group were generated on silicon substrates and reacted at room temperature with ~ 1 ppm gaseous ozone. A combination of experimental techniques including atomic force microscopy, scanning electron microscopy, Auger microprobe, time-of-flight secondary ion mass spectrometry, and transmission FTIR, were used to study the surface composition and morphology before and after oxidation. While the unreacted SAM was quite smooth, on the oxidized surface there were large (micron-size) organic aggregates and the surrounding substrate became depleted of carbon. This highly unusual result establishes that the mechanism of ozonolysis of alkene SAMs involves polymerization, likely induced by secondary reactions of the Criegee intermediate (CI). For that reason, formation of polymers under atmospheric conditions may be more common than previously recognized. The uptake of water was not increased upon oxidation of these films, in contrast to current expectations but consistent with the exposure of the substrate during reaction. The implications for SAM reactions and stability in air, ozonolysis of alkenes on surfaces, and for the oxidation of alkenes on airborne dust particles are discussed.
DE: 0305 Aerosols and particles (0345, 4801, 4906)
DE: 0317 Chemical kinetic and photochemical properties
SC: Atmospheric Sciences [A]
MN: Fall Meeting 2005