Liquid organization and solvation properties at polar solid/liquid interfaces

Area of Science:

• Physical Chemistry
• Surface Science
• Spectroscopy

Background:

• Understanding liquid organization at interfaces is crucial for chemical processes.
• Interfacial forces dictate molecular arrangement and properties.
• Nonlinear optical spectroscopy offers insights into interfacial molecular structure.

Purpose of the Study:

• To investigate liquid structure at the hydrophilic silica/liquid interface.
• To determine the influence of intermolecular forces versus steric effects on liquid organization.
• To examine how surface-mediated liquid structure affects solute solvation.

Main Methods:

• Employed second-order nonlinear optical spectroscopy.
• Utilized Vibrational Sum Frequency Generation (VSFG) spectroscopy.
• Applied Resonance Enhanced Second Harmonic Generation (SHG) spectroscopy.

Main Results:

• Cyclohexane structure at the silica/liquid interface mimicked the silica/vapor interface.
• Methylcyclohexane showed significant structural reorganization.
• 1-Propanol formed an ordered monolayer at both silica/vapor and silica/liquid interfaces.
• 2-Propanol exhibited different orientations at the silica/vapor and silica/liquid interfaces.
• Silica/alkane interfaces were more polar than expected; silica/alcohol interfaces showed alkane-like polarity due to reduced hydrogen bonding.

Conclusions:

• Intermolecular forces and steric effects significantly control liquid structure at the silica interface.
• Surface-mediated liquid structure alters interfacial polarity and solvation properties.
• The study highlights the sensitivity of molecular organization to the specific liquid and interface type.