Mechanisms for Enhanced Hydrophobicity by Atomic-Scale Roughness.
Yumi Katasho1, Yunfeng Liang1, Sumihiko Murata1
1Environment and Resource System Engineering, Kyoto University, Kyoto 615-8540, Japan.
Scientific Reports
|September 5, 2015
Summary
Roughened CF3 surfaces exhibit enhanced hydrophobicity due to a microscopic Cassie-Baxter state, widening the hydrophobic gap. CH3 surfaces show less hydrophobicity, existing in a Wenzel state with limited gap increase.
Area of Science:
- Surface Science
- Materials Chemistry
- Computational Physics
Background:
- Hydrophobic surfaces are crucial in various applications, with CF3-terminated surfaces known for their high hydrophobicity.
- Surface roughness is a key factor influencing the hydrophobic properties of materials.
Purpose of the Study:
- To investigate the effect of atomic-scale roughness on the hydrophobicity of CF3- and CH3-terminated surfaces.
- To elucidate the underlying mechanisms responsible for the differences in hydrophobic gap width between these surfaces.
Main Methods:
- Utilized molecular dynamic simulations to model and analyze the behavior of water molecules at roughened CF3- and CH3-terminated surfaces.
- Characterized the microscopic states (Cassie-Baxter vs. Wenzel) adopted by water on these surfaces.
Main Results:
- Atomic-scale roughness significantly enhances hydrophobicity on CF3-terminated surfaces, increasing the hydrophobic gap width to approximately 0.6 nm.
- Roughened CH3-terminated surfaces show a less pronounced increase in hydrophobic gap width.
- CF3-terminated surfaces adopt a microscopic Cassie-Baxter state, while CH3-terminated surfaces exhibit a microscopic Wenzel state.
Conclusions:
- The distinct microscopic states (Cassie-Baxter for CF3, Wenzel for CH3) explain the differing hydrophobic gap widths.
- Water molecule cage structure and hydrogen bonding around CH3 assemblies contribute to its lower hydrophobicity compared to CF3 surfaces.
