Nanoparticle halos: A new colloid stabilization mechanism
- *Department of Materials Science and Engineering and ‡Beckman Institute and Frederick Seitz Materials Research Laboratory, University of Illinois at Urbana-Champaign, Urbana, IL 61801; and †Department of Chemical Engineering, Carnegie Mellon University, Pittsburgh, PA 15213
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Edited by David Chandler, University of California, Berkeley, Berkeley, CA, and approved May 25, 2001 (received for review February 7, 2001)
Abstract
A new mechanism for regulating the stability of colloidal particles has been discovered. Negligibly charged colloidal microspheres, which flocculate when suspended alone in aqueous solution, undergo a remarkable stabilizing transition upon the addition of a critical volume fraction of highly charged nanoparticle species. Zeta potential analysis revealed that these microspheres exhibited an effective charge buildup in the presence of such species. Scanning angle reflectometry measurements indicated, however, that these nanoparticle species did not adsorb on the microspheres under the experimental conditions of interest. It is therefore proposed that highly charged nanoparticles segregate to regions near negligibly charged microspheres because of their repulsive Coulombic interactions in solution. This type of nanoparticle haloing provides a previously unreported method for tailoring the behavior of complex fluids.
Footnotes
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↵ § To whom reprint requests should be addressed. E-mail: jalewis{at}uiuc.edu.
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This paper was submitted directly (Track II) to the PNAS office.
- Copyright © 2001, The National Academy of Sciences
