title: The wetting-dewetting transition of monolayer water on a hydrophobic metal surface observed by surface-state resonant second-harmonic generation.
abstract: The isothermal adsorption and desorption of monolayer water on a Ag(110) surface in the temperature range of 130-137 K were characterized by monitoring second-harmonic (SH) generation from the silver surface. The SH intensity resonantly enhanced by the silver surface-state transition is highly sensitive to the amount of silver surface area covered by water and allows the observation of an abrupt change in the adsorption/desorption behavior at 133.5 K. At temperatures below 133.5 K water wets the Ag surface in a two-dimensional structure with a measured desorption energy of 25.0 (+/-3.3) kJ/mol. At temperatures greater than 133.5 K water desorbs from three-dimensional clusters with a measured desorption energy of 48.3 (+/-2.2) kJ/mol, in agreement with temperature-programmed desorption measurements. This wetting-dewetting transition of water adsorbed on the silver surface at 133.5 K is supported by classical nucleation theory calculations.
authors.affiliation: Department of Chemistry, University of Pennsylvania, Philadelphia, Pennsylvania 19104-6323, USA. sdounce@sas.upenn.edu
authors.forename: Susan M
authors.initials: SM
authors.lastname: Dounce
authors.forename: Shih-Hui
authors.initials: SH
authors.lastname: Jen
authors.forename: Minchul
authors.initials: M
authors.lastname: Yang
authors.forename: Hai-Lung
authors.initials: HL
authors.lastname: Dai