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Science. 2017 Apr 28;356(6336):434-437. doi: 10.1126/science.aah6902.

Direction-specific van der Waals attraction between rutile TiO2 nanocrystals.

Author information

1
Physical and Computational Sciences Directorate, Pacific Northwest National Laboratory, Richland, WA, USA.
2
Department of Mechanical Engineering and Materials Science, University of Pittsburgh, Pittsburgh, PA, USA.
3
Environmental Molecular Sciences Laboratory, Pacific Northwest National Laboratory, Richland, WA, USA.
4
Department of Mechanical Engineering and Materials Science, University of Pittsburgh, Pittsburgh, PA, USA. kevin.rosso@pnnl.gov chongmin.wang@pnnl.gov sxm2@pitt.edu.
5
Environmental Molecular Sciences Laboratory, Pacific Northwest National Laboratory, Richland, WA, USA. kevin.rosso@pnnl.gov chongmin.wang@pnnl.gov sxm2@pitt.edu.
6
Physical and Computational Sciences Directorate, Pacific Northwest National Laboratory, Richland, WA, USA. kevin.rosso@pnnl.gov chongmin.wang@pnnl.gov sxm2@pitt.edu.

Abstract

Mutual lattice orientations dictate the types and magnitudes of forces between crystalline particles. When lattice polarizability is anisotropic, the van der Waals dispersion attraction can, in principle, contribute to this direction dependence. We report measurement of this attraction between rutile nanocrystals, as a function of their mutual orientation and surface hydration extent. At tens of nanometers of separation, the attraction is weak and shows no dependence on azimuthal alignment or surface hydration. At separations of approximately one hydration layer, the attraction is strongly dependent on azimuthal alignment and systematically decreases as intervening water density increases. Measured forces closely agree with predictions from Lifshitz theory and show that dispersion forces can generate a torque between particles interacting in solution and between grains in materials.

PMID:
28450642
DOI:
10.1126/science.aah6902

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