Direction-specific van der Waals attraction between rutile TiO2 nanocrystals
Xin Zhang1, Yang He2, Maria L Sushko1
1Physical and Computational Sciences Directorate, Pacific Northwest National Laboratory, Richland, WA, USA.
Science (New York, N.Y.)
|April 29, 2017
Summary
Dispersion forces between rutile nanocrystals depend on orientation and hydration at close range. These forces can generate torque, impacting particle interactions in solutions and materials.
Area of Science:
- Materials Science
- Surface Chemistry
- Nanotechnology
Background:
- Mutual lattice orientations influence forces between crystalline particles.
- Anisotropic lattice polarizability suggests van der Waals dispersion attraction can be direction-dependent.
Purpose of the Study:
- Measure the van der Waals dispersion attraction between rutile nanocrystals.
- Investigate the influence of mutual orientation and surface hydration on this attraction.
Main Methods:
- Experimental measurement of forces between rutile nanocrystals.
- Varying nanocrystal separation, mutual orientation, and surface hydration.
Main Results:
- At large separations (tens of nanometers), attraction is weak and orientation-independent.
- At close separations (one hydration layer), attraction strongly depends on azimuthal alignment.
- Intervening water density systematically decreases attraction at close range.
Conclusions:
- Dispersion forces exhibit orientation and hydration dependence at the nanoscale.
- Lifshitz theory accurately predicts measured forces.
- Dispersion forces can induce torque between interacting particles in solution and within materials.
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