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Nanobubbles at the interface between water and a hydrophobic solid
Xue Hua Zhang1, Anthony Quinn, William A Ducker
1Department of Chemical and Biomolecular Engineering and Particulate Fluid Processing Center, University of Melbourne, Melbourne 3010, Australia.
Langmuir : the ACS Journal of Surfaces and Colloids
|March 28, 2008
Summary
Stable, ultrathin gas films form at hydrophobic solid-water interfaces. These interfacial gas bubbles, characterized by infrared spectroscopy and atomic force microscopy, demonstrate unique pressure and stability properties.
Area of Science:
- Interfacial Science
- Physical Chemistry
- Materials Science
Background:
- A stable, ultrathin gas layer (5-80 nm) can exist at the interface between hydrophobic solids and water.
- This gas layer consists of discrete bubbles containing approximately 40,000 molecules.
Purpose of the Study:
- To investigate the properties and stability of interfacial gas films.
- To characterize the gas phase at the hydrophobic solid-water interface using spectroscopic and microscopic techniques.
Main Methods:
- Attenuated total internal reflection infrared spectroscopy (ATIR-IR) to analyze gas composition and pressure.
- Atomic force microscopy (AFM) to determine bubble dimensions and curvature.
- Solvent exchange method for preparing interfacial gas films from ambient air or CO2.
- Surface plasmon resonance (SPR) to confirm the gas state of the film.
Main Results:
- Rotational fine structure in IR spectra confirmed the presence of CO2 and D2O in the gas phase.
- Air bubbles exhibited stability exceeding 4 days, while CO2 bubbles lasted 1-2 hours.
- IR spectroscopy indicated average CO2 bubble pressures between 1.0 and 1.5 atm.
- AFM and Laplace pressure calculations showed bubble pressures ranging from 1.0 to 1.7 atm.
- Lower atmospheric pressure and higher solubility of CO2 contribute to its reduced stability compared to air bubbles.
Conclusions:
- Interfacial gas films are stable under specific conditions at hydrophobic-water interfaces.
- Bubble stability is influenced by gas composition, ambient pressure, and solubility.
- The study provides insights into the physics and chemistry of interfacial gas phases.
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