title: Attenuated total reflectance infrared spectroscopy study of hysteresis of water and n-alcohol coadsorption on silicon oxide.
abstract: The structure and thickness of the binary adsorbate layers formed on silicon oxide exposed in n-propanol/water and n-pentanol/water vapor mixtures under atmospheric pressure and room temperature conditions were investigated using attenuated total reflectance infrared spectroscopy (ATR-IR). The ATR-IR spectra of the adsorbate layers were analyzed while the vapor composition was varied stepwise by changing the mixing ratios of (a) n-propanol vapor stream with a 94% relative partial pressure (P/P(sat)) and 94% P/P(sat) water stream and (b) 83% P/P(sat)n-pentanol and 85% P/P(sat) water streams. The amount of the adsorbed water with solid-like structure in the binary adsorbate layer was larger in successive cycles of the water/alcohol vapor composition change, while n-alcohol showed negligible hysteresis in the amount adsorbed. The hysteresis behavior of the solid-like water structure was amplified in the coadsorption cycles of alcohol and water as compared to the water-only case. The origin of this behavior must be attributed to the structure of the alcohol/water binary adsorbate layer. The n-alcohol molecules present at the adsorbate/vapor interface can lower the surface energy of the system and stabilize the solid-like water structure in the alcohol-water binary adsorbate layer on silicon oxide.
authors.affiliation: Department of Chemical Engineering, The Pennsylvania State University, University Park, 16802, United States.
authors.forename: Anna L
authors.initials: AL
authors.lastname: Barnette
authors.forename: Seong H
authors.initials: SH
authors.lastname: Kim
mesh_terms: D000327:Adsorption; D000438:Alcohols / Q000737:chemistry*; D012822:Silicon Dioxide / Q000737:chemistry*; D017550:Spectroscopy, Fourier Transform Infrared; D013499:Surface Properties; D014867:Water / Q000737:chemistry*
chemical_list: D000438:Alcohols; D014867:Water; D012822:Silicon Dioxide