| AVS 57th International Symposium & Exhibition | |
| Surface Science | Friday Sessions |
| Session SS-FrM |
| Session: | Reactivity of Oxides, Mainly TiO2 |
| Presenter: | Z. Dohnalek, Pacific Northwest National Laboratory |
| Authors: | Z. Zhang, Pacific Northwest National Laboratory R.J. Rousseau, Pacific Northwest National Laboratory J. Gong, University of Texas at Austin B.D. Kay, Pacific Northwest National Laboratory Z. Dohnalek, Pacific Northwest National Laboratory |
| Correspondent: | Click to Email |
The first scanning tunneling microscopy (STM) study of the rotational dynamics of organic species on oxides is presented. Variable-temperature STM and dispersion-corrected density functional theory (DFT-D) are used to study the alkyl chain conformational disorder and dynamics of 1-, 2-, 3- and 4-octoxy species on rutile TiO2(110). Initially, the geminate pairs of the octoxy and bridging hydroxyl species are created via octanol dissociation on bridging-oxygen (Ob) vacancy defects. The STM images provide time averaged snapshots of octoxy species rotating among multiple energetically nearly-degenerate configurations accessible at a given temperature. The calculations show that the underlying corrugated potential energy surface is a result of the interplay between attractive van der Waals dispersion forces leading to weak attractive C…Ti and repulsive C…Ob interactions which lead to large barriers of 50-70kJmol-1 for the rotation of the octoxy alkyl chains across the Ob rows. The relative populations of various conformations as well as the rotational barriers are found to be perturbed as a result of additional C…hydroxyl repulsions when the geminate hydroxyl groups are present.
This research was performed in the Environmental Molecular Sciences Laboratory, a national scientific user facility sponsored by the Department of Energy's Office of Biological and Environmental Research and located at Pacific Northwest National Laboratory.