TY - JOUR
T1 - Adsorption of H2O, CO2 and Xe on soft surfaces
AU - Stein, Ori
AU - Asscher, Micha
PY - 2008/4/3
Y1 - 2008/4/3
N2 - The interactions of water, carbon dioxide, and Xe with octadecanethiol (C18H37SH, ODT) self-assembled monolayers (SAMs) were studied under ultrahigh vacuum conditions employing temperature-programmed desorption and optical diffraction measurements. The ODT layer was grown on a 1 nm thick gold film deposited over a Ru(001) single-crystal substrate. The gases used in this report differ in their lateral interactions while adsorbed on ODT-SAM being either repulsive (Xe) or attractive (H2O, CO 2). The activation energies for desorption of the first layer from ODT are Ea = 3.6 ± 0.9, 4.1 ± 0.5, and 8.5 ±0.9 kcal/mol for Xe, CO2, and H2O, respectively. Sticking probabilities of the three gases on the soft ODT surface are S0 = 0.7 ± 0.1, 0.8 ± 0.1, and 0.95 ± 0.05 for xenon, CO 2, and water, respectively, derived from the respective adsorption curves. Optical diffraction studies from multilayer coverage grating of Xe on ODT-SAM have demonstrated that sublimation is a thermodynamically more favorable process over diffusion and wetting. The significantly lower binding energy of the first layers of H2O and CO2 adsorbed on the soft surface of ODT compared to that on clean metals and oxides, reflects generally weak (CO2) and hydrophobic (H2O) interactions that are important for understanding the behavior of these molecules on interfaces that are found in biological systems.
AB - The interactions of water, carbon dioxide, and Xe with octadecanethiol (C18H37SH, ODT) self-assembled monolayers (SAMs) were studied under ultrahigh vacuum conditions employing temperature-programmed desorption and optical diffraction measurements. The ODT layer was grown on a 1 nm thick gold film deposited over a Ru(001) single-crystal substrate. The gases used in this report differ in their lateral interactions while adsorbed on ODT-SAM being either repulsive (Xe) or attractive (H2O, CO 2). The activation energies for desorption of the first layer from ODT are Ea = 3.6 ± 0.9, 4.1 ± 0.5, and 8.5 ±0.9 kcal/mol for Xe, CO2, and H2O, respectively. Sticking probabilities of the three gases on the soft ODT surface are S0 = 0.7 ± 0.1, 0.8 ± 0.1, and 0.95 ± 0.05 for xenon, CO 2, and water, respectively, derived from the respective adsorption curves. Optical diffraction studies from multilayer coverage grating of Xe on ODT-SAM have demonstrated that sublimation is a thermodynamically more favorable process over diffusion and wetting. The significantly lower binding energy of the first layers of H2O and CO2 adsorbed on the soft surface of ODT compared to that on clean metals and oxides, reflects generally weak (CO2) and hydrophobic (H2O) interactions that are important for understanding the behavior of these molecules on interfaces that are found in biological systems.
UR - http://www.scopus.com/inward/record.url?scp=45849084700&partnerID=8YFLogxK
U2 - 10.1021/jp7099493
DO - 10.1021/jp7099493
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C2 - 18324804
AN - SCOPUS:45849084700
SN - 1520-6106
VL - 112
SP - 3955
EP - 3962
JO - Journal of Physical Chemistry B
JF - Journal of Physical Chemistry B
IS - 13
ER -