Lattice-scale variations in viscosity are correlated with solution structure at mineral-water interfaces

Area of Science:

• Physical Chemistry
• Surface Science
• Nanotechnology

Background:

• Viscosity increases significantly at solid-liquid interfaces due to ion and water molecule interactions.
• This phenomenon is crucial for understanding nanofluidics, colloidal dynamics, and electrochemistry.

Purpose of the Study:

• To investigate dissipative forces and interfacial solution viscosity at the boehmite-water interface.
• To correlate interfacial viscosity with crystal lattice structure and solution structure.

Main Methods:

• 3D atomic force microscopy (AFM) for direct measurement.
• Molecular dynamics (MD) simulations for detailed analysis.
• Statistical mechanical analysis for theoretical insights.

Main Results:

• Interfacial viscosity (η) increased 10-100 fold approaching the surface, with peaks up to 44-71 times bulk viscosity.
• Sub-nanometer variations in viscosity were observed within 0.5 nm of the interface, templated by the crystal lattice.
• Anisotropic viscosity and increased friction were linked to hydrogen bonding of interfacial water, especially along the [001] direction.

Conclusions:

• Solution viscosity at mineral-water interfaces is anisotropic and structurally dependent.
• Interfacial water structure and hydrogen bonding significantly influence dissipative forces.
• Findings provide insights into nanocrystal attachment dynamics at interfaces.