Prof. Heather Allen, Ohio State University

Structure at Air - Aqueous Interfaces: Lipids, Salts, Acids, and Water

Water's ability to hydrate molecular and ionic compounds is critically important for the understanding of many chemical and physical processes. Our interest in lung lining and atmospheric aerosols has led us to investigate the fundamental process of hydration at the air - aqueous interface, and in aqueous solutions. Vibrational spectroscopies, infrared, Raman, and surface-selective sum frequency generation (SFG), are utilized to elucidate these effects. Halides are surface active; however, when hydronium is the counter ion, the hydronium itself plays the leading role in surface propensity. Dications are shown to be very different at the air-water interface as compared to bulk hydration and ion-pairing studies. We reveal that nitrate anions approach the air-water interface as relatively free anions when the counter ion is magnesium. Additional ion pairing and hydration effects are discussed. In our studies of lung surfactant model systems, water hydration is interestingly different. The dangling water bonds at the surface of Langmuir monolayers are observed to interact with the lipid tails of surfactant systems, causing significant perturbation of the dangling OD bond of D2O. Temperature studies further explain this finding.

For more information contact Dr. Paul Wine (404-894-3425).