Variable Interfacial Water Nanosized Arrangements Measured by Atomic Force Microscopy

Area of Science:

• Physical Chemistry
• Surface Science
• Materials Science

Background:

• Cluster formation near solid surfaces is accepted.
• The existence of water clusters at the liquid/vapor interface remains debated.
• Understanding interfacial water structure is crucial for various scientific disciplines.

Purpose of the Study:

• To experimentally investigate the presence and characteristics of water clusters at the liquid/vapor interface.
• To analyze the structural and dielectric properties of interfacial water on different surfaces.
• To determine the temporal evolution of interfacial water structures.

Main Methods:

• Experimental force vs distance measurements on water attached to hydrophobic and hydrophilic surfaces.
• Analysis of nanosized steps in force-distance curves to characterize water cluster profiles.
• Investigation of the dielectric permittivity profile of interfacial water.

Main Results:

• Nanosized steps in force-distance curves indicate the presence of water cluster profiles.
• Interfacial water structures expand over time, from ~1 nm initially to ~70 nm.
• Interfacial dielectric permittivity exhibits an oscillating profile, differing from homogeneous bulk water.
• Low dielectric permittivity clusters extend into the bulk water, resembling expanding water networks.

Conclusions:

• Experimental evidence supports the existence of water cluster formation at the liquid/vapor interface.
• Interfacial water exhibits dynamic structural expansion and complex dielectric behavior.
• The observed phenomena suggest a network-like behavior of interfacial water structures that evolve over time.