AVS 52nd International Symposium
    Applied Surface Science Wednesday Sessions
       Session AS-WeA

Paper AS-WeA1
Analysis of a Model System for Reactions of Organic Molecules on Atmospheric Particles: SAMS and Ozone

Wednesday, November 2, 2005, 2:00 pm, Room 206

Session: SIMS Cluster Probe Beams and General Topics
Presenter: D.J. Gaspar, Pacific Northwest National Laboratory
Authors: D.J. Gaspar, Pacific Northwest National Laboratory
T.M. McIntire, University of California, Irvine
A.S. Lea, Pacific Northwest National Laboratory
N. Jaitly, Pacific Northwest National Laboratory
Y. Dubowski, Technion-Israel Institute of Technology
B.J. Finlayson-Pitts, University of California, Irvine
Correspondent: Click to Email
Self-assembled monolayers (SAMS) provide a useful model system for the study of reactions of organic molecules. The preparation, use and analysis of SAMS are prone to variability and artifacts that can confound measurements that are do not provide molecular information on the state of the surface. Time of flight secondary ion mass spectrometry, on the other hand, provides a direct probe of the SAM surface chemistry. In this work, we describe our efforts to extract useful information regarding the reaction of ozone with saturated and unsaturated organic monolayers covalently bound to silicon dioxide surfaces under atmospherically relevant conditions. We have used a combination of imaging TOF-SIMS and spectral analysis aided by principal component analysis (PCA) to extract chemical information about the reaction of two model SAMS with ozone. The TOF-SIMS data provide the molecular information necessary to accurately interpret data obtained using other methods and described herein, including atomic force microscopy (AFM), attenuated total reflectance Fourier transform infrared spectroscopy (ATR-FTIR), and scanning Auger microscopy (AES). We show that the organic monolayer is removed from the Si substrate by ozone for an unsaturated 1-octene (C8=) monolayer, while it remains intact for a saturated dodecane (C12) monolayer. The implications of these observations for the atmospheric chemistry of organic molecules are discussed.