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Rationalization of the behavior of solid-liquid surface free energy of water in Cassie and Wenzel wetting states on rugged solid surfaces at the nanometer scale.
Langmuir. 2011 Jan 18; 27(2):637-45.L

Abstract

The present work aims to contribute to the understanding at a molecular level of the origin of the hydrophobic nature of surfaces exhibiting roughness at the nanometer scale. Graphite-based smooth and model surfaces whose roughness dimension stretches from a few angstroms to a few nanometers were used in order to generate Cassie and Wenzel wetting states of water. The corresponding solid-liquid surface free energies were computed by means of molecular dynamics simulations. The solid-liquid surface free energy of water-smooth graphite was found to be -12.7 ± 3.3 mJ/m(2), which is in reasonable agreement with a value estimated from experiments and fully consistent with the features of the employed model. All the rugged surfaces yielded higher surface free energy. In both Cassie and Wenzel states, the maximum variation of the surface free energy with respect to the smooth surface was observed to represent up to 50% of the water model surface tension. The solid-liquid surface free energy of Cassie states could be well predicted from the Cassie-Baxter equation where the surface free energies replace contact angles. The origin of the hydrophobic nature of surfaces yielding Cassie states was therefore found to be the reduction of the number of interactions between water and the solid surface where atomic defects were implemented. Wenzel's theory was found to fail to predict even qualitatively the variation of the solid-liquid surface free energy with respect to the roughness pattern. While graphite was found to be slightly hydrophilic, Wenzel states were found to be dominated by an unfavorable effect that overcame the favorable enthalpic effect induced by the implementation of roughness. From the quantitative point of view, the solid-liquid surface free energy of Wenzel states was found to vary linearly with the roughness contour length.

Authors+Show Affiliations

Eduard-Zintl-Institut für Anorganische und Physikalische Chemie and Center of Smart Interfaces, Technische Universität Darmstadt, Petersenstrasse 22, 64287 Darmstadt, Germany. f.leroy@theo.chemie.tu-darmstadt.deNo affiliation info available

Pub Type(s)

Journal Article
Research Support, Non-U.S. Gov't

Language

eng

PubMed ID

21142209

Citation

Leroy, Frédéric, and Florian Müller-Plathe. "Rationalization of the Behavior of Solid-liquid Surface Free Energy of Water in Cassie and Wenzel Wetting States On Rugged Solid Surfaces at the Nanometer Scale." Langmuir : the ACS Journal of Surfaces and Colloids, vol. 27, no. 2, 2011, pp. 637-45.
Leroy F, Müller-Plathe F. Rationalization of the behavior of solid-liquid surface free energy of water in Cassie and Wenzel wetting states on rugged solid surfaces at the nanometer scale. Langmuir. 2011;27(2):637-45.
Leroy, F., & Müller-Plathe, F. (2011). Rationalization of the behavior of solid-liquid surface free energy of water in Cassie and Wenzel wetting states on rugged solid surfaces at the nanometer scale. Langmuir : the ACS Journal of Surfaces and Colloids, 27(2), 637-45. https://doi.org/10.1021/la104018k
Leroy F, Müller-Plathe F. Rationalization of the Behavior of Solid-liquid Surface Free Energy of Water in Cassie and Wenzel Wetting States On Rugged Solid Surfaces at the Nanometer Scale. Langmuir. 2011 Jan 18;27(2):637-45. PubMed PMID: 21142209.
* Article titles in AMA citation format should be in sentence-case
TY - JOUR T1 - Rationalization of the behavior of solid-liquid surface free energy of water in Cassie and Wenzel wetting states on rugged solid surfaces at the nanometer scale. AU - Leroy,Frédéric, AU - Müller-Plathe,Florian, Y1 - 2010/12/13/ PY - 2010/12/15/entrez PY - 2010/12/15/pubmed PY - 2011/5/6/medline SP - 637 EP - 45 JF - Langmuir : the ACS journal of surfaces and colloids JO - Langmuir VL - 27 IS - 2 N2 - The present work aims to contribute to the understanding at a molecular level of the origin of the hydrophobic nature of surfaces exhibiting roughness at the nanometer scale. Graphite-based smooth and model surfaces whose roughness dimension stretches from a few angstroms to a few nanometers were used in order to generate Cassie and Wenzel wetting states of water. The corresponding solid-liquid surface free energies were computed by means of molecular dynamics simulations. The solid-liquid surface free energy of water-smooth graphite was found to be -12.7 ± 3.3 mJ/m(2), which is in reasonable agreement with a value estimated from experiments and fully consistent with the features of the employed model. All the rugged surfaces yielded higher surface free energy. In both Cassie and Wenzel states, the maximum variation of the surface free energy with respect to the smooth surface was observed to represent up to 50% of the water model surface tension. The solid-liquid surface free energy of Cassie states could be well predicted from the Cassie-Baxter equation where the surface free energies replace contact angles. The origin of the hydrophobic nature of surfaces yielding Cassie states was therefore found to be the reduction of the number of interactions between water and the solid surface where atomic defects were implemented. Wenzel's theory was found to fail to predict even qualitatively the variation of the solid-liquid surface free energy with respect to the roughness pattern. While graphite was found to be slightly hydrophilic, Wenzel states were found to be dominated by an unfavorable effect that overcame the favorable enthalpic effect induced by the implementation of roughness. From the quantitative point of view, the solid-liquid surface free energy of Wenzel states was found to vary linearly with the roughness contour length. SN - 1520-5827 UR - https://www.unboundmedicine.com/medline/citation/21142209/Rationalization_of_the_behavior_of_solid_liquid_surface_free_energy_of_water_in_Cassie_and_Wenzel_wetting_states_on_rugged_solid_surfaces_at_the_nanometer_scale_ L2 - https://dx.doi.org/10.1021/la104018k DB - PRIME DP - Unbound Medicine ER -