Ordered water structure at hydrophobic graphite interfaces observed by 4D, ultrafast electron crystallography

Area of Science:

• Materials Science
• Physical Chemistry
• Surface Science

Background:

• Interfacial water exhibits unique properties crucial for various applications.
• Understanding the structure and dynamics of water at hydrophobic interfaces is essential.
• Previous expectations suggested suppressed order due to strong hydrogen bonding on hydrophobic surfaces.

Purpose of the Study:

• To investigate the structure and dynamics of interfacial water assembly on a hydrophobic surface.
• To challenge existing hypotheses regarding water ordering at hydrophobic interfaces.
• To elucidate the phase transformation dynamics of interfacial water.

Main Methods:

• Utilized 4-dimensional (4D), ultrafast electron crystallography.
• Achieved atomic-scale spatial and temporal resolution.
• Employed infrared pulse excitation of the hydrophobic surface.

Main Results:

• Determined vertically stacked, ordered water bilayers on highly oriented pyrolytic graphite.
• Observed a nonequilibrium phase transformation in the interfacial ice structure.
• Identified the transformation via structural isosbestic points in the hydrogen-bond network.

Conclusions:

• Hydrophobic graphite's terrace morphology acts as a template, promoting interfacial water order.
• The observed phase transformation reveals novel ice-graphite structural dynamics.
• Findings are relevant to understanding the properties of confined water.