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Hamaker constants of iron oxide nanoparticles
Bertrand Faure1, German Salazar-Alvarez, Lennart Bergström
1Department of Materials and Environmental Chemistry, Stockholm University, Stockholm, Sweden.
Langmuir : the ACS Journal of Surfaces and Colloids
|June 8, 2011
Summary
This study calculated Hamaker constants for iron oxide nanoparticles using Lifshitz theory. Results show lower values in nonpolar solvents, impacting colloidal stability and self-assembly predictions.
Area of Science:
- Materials Science
- Physical Chemistry
- Nanotechnology
Background:
- Accurate Hamaker constants are crucial for understanding nanoparticle interactions.
- Previous estimates for iron oxide nanoparticles in nonpolar solvents may require revision.
Purpose of the Study:
- To calculate Hamaker constants for iron oxide nanoparticles (magnetite, maghemite, hematite) in water and nonpolar solvents using Lifshitz theory.
- To re-evaluate colloidal stability and self-assembly theories based on new Hamaker constant values.
Main Methods:
- Lifshitz theory was applied to calculate Hamaker constants.
- Dielectric responses were derived from published optical data for iron oxide phases.
- Calculations were performed for interactions in water, hexane, and toluene.
Main Results:
- Nonretarded Hamaker constants in water (A(1w1) = 33–39 zJ) align with previous reports.
- Calculated values in nonpolar solvents (A(131) = 9–29 zJ) are significantly lower than prior estimates, especially for magnetite.
- Van der Waals interaction magnitudes differ across iron oxide phases: magnetite < maghemite < hematite.
Conclusions:
- The study provides updated Hamaker constant values for iron oxide nanoparticles, particularly in nonpolar media.
- Accurate particle characterization is essential due to phase-dependent van der Waals interactions.
- New data necessitates revisiting theories on nanoparticle colloidal stability and self-assembly.
