| AVS 59th Annual International Symposium and Exhibition | |
| Surface Science | Thursday Sessions |
| Session SS-ThA |
| Session: | Liquid/Surface Interactions |
| Presenter: | K.A. Perrine, University of California Irvine |
| Authors: | K.A. Perrine, University of California Irvine A. Margarella, University of California Irvine M.H.C. Van Spyk, University of California Irvine B. Winter, Helmholtz-Zentrum Berlin für Materialien und Energie, Germany H. Bluhm, Lawrence Berkeley National Laboratory J.C. Hemminger, University of California Irvine |
| Correspondent: | Click to Email |
It is important to understand the molecular-level properties of aqueous organic mixtures that can affect the environment as well as a variety of chemical systems. Mixtures of acetonitrile and water solutions have been shown to have different properties at the surface and in the bulk at different bulk acetonitrile concentrations. According to surface sensitive studies and molecular dynamic simulations, at 0.07 mole fraction, hydrogen bonding is lost at the interface with increasing acetonitrile concentration, leading to a reorientation of the acetonitrile at the surface. In addition, water and acetonitrile clusters have been shown to coexist and interact by dipole interactions between 0.2 and 0.8 mole fraction of acetonitrile. The reorientation of another nitrile at the surface, propionitrile, by hydrogen bonding has also been observed, but for this molecule, there is a lack of bulk studies of water-nitrile solutions.
In our studies, liquid-jet X-ray photoelectron spectroscopy was used to determine the nature of aqueous solutions of these two nitriles. The C1s, N1s and O1s regions suggest that clustering of the nitrile and water is apparent at the surface as well as the bulk. A full range of nitrile concentrations was studied. In addition, we made comparisons between experiments in which the liquid jet is in contact with a few torr of vapor and experiments in which the jet is exposed to high vacuum. The surface and bulk properties, as determined by XPS, are the same under these two experimental conditions. Our results also allow us to compare the differences between solubility of the two nitrile aqueous solutions and their hydrogen bonding properties at the surface and in the bulk.