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Direct Measurement of Sub-Debye-Length Attraction between Oppositely Charged Surfaces Nir Kampf,1
 

Summary: Direct Measurement of Sub-Debye-Length Attraction between Oppositely Charged Surfaces
Nir Kampf,1
Dan Ben-Yaakov,2
David Andelman,2
S. A. Safran,1
and Jacob Klein1,*
1
Department of Materials and Interfaces, Weizmann Institute of Science, Rehovot 76100, Israel
2
Raymond and Beverly Sackler School of Physics and Astronomy, Tel Aviv University, Ramat Aviv, Tel Aviv 69978, Israel
(Received 15 May 2009; published 11 September 2009)
Using a surface force balance with fast video analysis, we have measured directly the attractive forces
between oppositely charged solid surfaces (charge densities , ) across water over the entire range of
interaction, in particular, at surface separations D below the Debye screening length S. At very low salt
concentration we find a long-ranged attraction between the surfaces (onset ca. 100 nm), whose variation at
D < S agrees well with predictions based on solving the Poisson-Boltzmann theory, when due account is
taken of the independently-determined surface charge asymmetry ( jj).
DOI: 10.1103/PhysRevLett.103.118304 PACS numbers: 82.70.y, 07.10.Pz, 82.45.Mp
The Debye-Huckel, and more generally the Derjaguin-
Landau-Verwey-Overbeek approach, based on lineariza-

  

Source: Andelman, David - School of Physics and Astronomy, Tel Aviv University
Klein, Jacob - Department of Materials and Interfaces, Weizmann Institute of Science

 

Collections: Materials Science; Physics