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Updated: Jan 19, 2026
Multiscale Sampling of a Heterogeneous Water/Metal Catalyst Interface using Density Functional Theory and Force-Field Molecular Dynamics
Published on: April 12, 2019
Probing effects of molecular-level heterogeneity of surface hydrophobicity on hydrophobic interactions in
1Department of Chemical and Materials Engineering, University of Alberta, Edmonton, Alberta T6G 2V4, Canada.
Hypothesis:
Hydrophobic interaction is crucial in various colloidal phenomena and engineering processes involving air/water/solid systems where polar and nonpolar substances usually mingle with each other. The molecular-level heterogeneity of surface hydrophobicity could potentially disorder the interfacial water molecules and thus influence the hydrophobic interaction strength, but the underlying mechanism is not completely clear.
Experiments:
The hydrophobic interactions between air bubbles and self-assembled monolayer surfaces bearing methyl and different polar moieties were precisely quantified via bubble probe atomic force microscope coupled with theoretical modeling analysis.
Findings:
Increasing coverage of surface polar moieties on binary-component surfaces can apparently lower surface hydrophobicity θc, but hardly affect hydrophobic interaction's decay length D0. Changing pH has no detectable effect on hydrophobic interactions involving CH3 and CH3/OH-ended surfaces. In contrast, θc and D0 decrease monotonically with pH rising for CH3/COOH-ended surface, because high pH tends to dissociate -COOH, enhancing the surface hydrophilicity and weakening the hydrophobic interaction. For CH3/NH2-ended surface, θc and D0 decrease sequentially with pH declining, because protonation of -NH2 can lower the surface hydrophobicity and weaken the hydrophobic interaction. This work improves the fundamental understanding of hydrophobic interactions in air/water/solid systems and provides useful insights into the interfacial assembly processes in relevant engineering applications.
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