Attenuated Total Reflectance Infrared Spectroscopy Study of Hysteresis of Water and n-Alcohol Coadsorption on Silicon Oxide

作者：Barnette Anna L; Kim Seong H^*

来源：Langmuir, 2012, 28(44): 15529-15536.

DOI：10.1021/la302849t

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.

• 出版日期2012-11-6