title: Measurements of dispersion forces between colloidal latex particles with the atomic force microscope and comparison with Lifshitz theory.
abstract: Interaction forces between carboxylate colloidal latex particles of about 2 μm in diameter immersed in aqueous solutions of monovalent salts were measured with the colloidal probe technique, which is based on the atomic force microscope. We have systematically varied the ionic strength, the type of salt, and also the surface charge densities of the particles through changes in the solution pH. Based on these measurements, we have accurately measured the dispersion forces acting between the particles and estimated the apparent Hamaker constant to be (2.0 ± 0.5) × 10(-21) J at a separation distance of about 10 nm. This value is basically independent of the salt concentration and the type of salt. Good agreement with Lifshitz theory is found when roughness effects are taken into account. The combination of retardation and roughness effects reduces the value of the apparent Hamaker constant and its ionic strength dependence with respect to the case of ideally smooth surfaces.
authors.affiliation: Department of Inorganic and Analytical Chemistry, University of Geneva, Sciences II, 30, Quai Ernest-Ansermet, 1205 Geneva, Switzerland.
authors.forename: Magdalena
authors.initials: M
authors.lastname: Elzbieciak-Wodka
authors.affiliation: Ian Wark Research Institute, University of South Australia, Mawson Lakes, SA 5095, Australia.
authors.forename: Mihail N
authors.initials: MN
authors.lastname: Popescu
authors.affiliation: Department of Inorganic and Analytical Chemistry, University of Geneva, Sciences II, 30, Quai Ernest-Ansermet, 1205 Geneva, Switzerland.
authors.forename: F Javier
authors.initials: FJ
authors.lastname: Montes Ruiz-Cabello
authors.affiliation: Department of Inorganic and Analytical Chemistry, University of Geneva, Sciences II, 30, Quai Ernest-Ansermet, 1205 Geneva, Switzerland.
authors.forename: Gregor
authors.initials: G
authors.lastname: Trefalt
authors.affiliation: Department of Inorganic and Analytical Chemistry, University of Geneva, Sciences II, 30, Quai Ernest-Ansermet, 1205 Geneva, Switzerland.
authors.forename: Plinio
authors.initials: P
authors.lastname: Maroni
authors.affiliation: Department of Inorganic and Analytical Chemistry, University of Geneva, Sciences II, 30, Quai Ernest-Ansermet, 1205 Geneva, Switzerland.
authors.forename: Michal
authors.initials: M
authors.lastname: Borkovec