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How water meets a very hydrophobic surface
Sudeshna Chattopadhyay1, Ahmet Uysal, Benjamin Stripe
1Department of Physics & Astronomy, Northwestern University, Evanston, Illinois 60208, USA.
Physical Review Letters
|September 28, 2010
Summary
A low-density gap between water and hydrophobic surfaces was definitively measured using x-ray reflectivity. The gap
Area of Science:
- Surface Science
- Physical Chemistry
- Materials Science
Background:
- The existence of a low-density region at the water-hydrophobic surface interface is debated.
- Previous reflectivity studies yielded inconsistent results due to limitations in resolution.
Purpose of the Study:
- To definitively measure the water-hydrophobic interface structure.
- To investigate the relationship between surface hydrophobicity and interface structure.
Main Methods:
- Utilized high-resolution x-ray reflectivity.
- Probed interfaces between water and increasingly hydrophobic smooth surfaces.
Main Results:
- A measurable depleted region (gap) exists at the water-hydrophobic interface.
- The width of this depleted region increases with surface contact angle.
- Interface fluctuations predicted by theory were found to be too small to measure.
Conclusions:
- Confirms the presence of a distinct low-density region at hydrophobic interfaces.
- Provides quantitative data on the dependence of this region on hydrophobicity.
- Suggests that large interfacial fluctuations are not a dominant feature.
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