Real Time Monitoring of Self Assembled Monolayers Using ATR: Implications to Atmospheric Organic Surfaces

December 10, 2003 - 12:00pm
Bldg. 90
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Most studies of heterogeneous reactions on aerosols have focused on their implications for gas phase species. Less attention, however, has been given to the modification of aerosol surfaces during such reactions. Alteration of aerosol surface species may affect their hygroscopic and radiative properties as well as their reactivity toward other atmospheric trace species. In the present study, we use self-assembled organic monolayers (SAM) as proxies for atmospheric organic aerosols. Detection of even very short carbon chains (i.e., C3) as well as continuous monitoring of the SAMs during the experiments are achieved by depositing the SAMs directly on a silicon attenuated total reflection (ATR) crystal (10 reflections) attached to a FTIR.  The oxidation kinetics of unsaturated SAMs by ozone are studied using this technique, as a function of carbon chain length. Reaction probabilities are calculated based on surface oxidation and compared to molecular dynamic simulations of such systems and to probabilities previously calculated by gas phase monitoring. The atmospheric implications will be discussed.

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