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Finite Volume Effects in Water Nanodroplets: A Molecular Level Investigation
Li Zhang1, Saranya Pullanchery1, Paul S Cremer2
1Laboratory for Fundamental BioPhotonics, Institute of Bioengineering (IBI), School of Engineering (STI), École Polytechnique Fédérale de Lausanne (EPFL), CH-1015 Lausanne, Switzerland.
ACS Nano
|June 24, 2025
Summary
Finite volume effects significantly alter water structure at nanoscale interfaces. Water nanodroplets in oil show distinct molecular coupling compared to oil nanodroplets in water, revealing interface heterogeneity.
Area of Science:
- Physical chemistry
- Nanoscale science
- Interface science
Background:
- Aqueous interfaces govern numerous processes.
- Finite volume effects significantly influence nanoscale interfaces, impacting molecular and macroscopic properties.
Purpose of the Study:
- Investigate finite volume effects on aqueous interfaces.
- Characterize water structure and molecular coupling at oil-water interfaces.
Main Methods:
- Electrophoretic mobility measurements.
- Vibrational sum frequency scattering spectroscopy.
- Isotope dilution studies on water nanodroplets in oil and oil nanodroplets in water.
Main Results:
- Substantial differences in water orientational ordering observed between the two interface types.
- Water outside droplets shows significant intramolecular coupling; water inside predominantly exhibits intermolecular coupling.
- Spectral variations indicate greater heterogeneity within water droplets, attributed to finite volume effects and electrostatic differences.
Conclusions:
- Finite volume effects create distinct water structures and molecular coupling at nanoscale interfaces.
- Water droplet heterogeneity is a key consequence of confinement and electrostatics.
- Understanding these interfacial phenomena is crucial for processes involving nanoscale aqueous systems.
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