title: Forces between silica particles in the presence of multivalent cations.
abstract: Forces between negatively charged silica particles in aqueous electrolyte solutions were measured with the colloidal probe technique based on the atomic force microscope (AFM). The present study focuses on the comparison of monovalent and multivalent counterions, namely K(+), Mg(2+), and La(3+). The force profiles can be well described with the theory of Derjaguin, Landau, Verwey, and Overbeek (DLVO) down to distances of about 4 nm. At smaller distances, the forces become strongly repulsive due to additional non-DLVO repulsion. In the presence of La(3+), one observes an additional attractive force with a range of about 1 nm at intermediate salt concentrations. This force is probably related to ion-ion correlations, but could also be influenced by surface charge heterogeneities or charge fluctuation forces.
authors.affiliation: Department of Inorganic and Analytical Chemistry, University of Geneva, Sciences II, Quai Ernest-Ansermet 30, 1205 Geneva, Switzerland.
authors.forename: Valentina
authors.initials: V
authors.lastname: Valmacco
authors.affiliation: J. Haber Institute of Catalysis and Surface Chemistry, Polish Academy of Sciences, Niezapominajek 8, 30-239 Cracow, Poland.
authors.forename: Magdalena
authors.initials: M
authors.lastname: Elzbieciak-Wodka
authors.affiliation: Department of Inorganic and Analytical Chemistry, University of Geneva, Sciences II, Quai Ernest-Ansermet 30, 1205 Geneva, Switzerland.
authors.forename: David
authors.initials: D
authors.lastname: Herman
authors.affiliation: Department of Inorganic and Analytical Chemistry, University of Geneva, Sciences II, Quai Ernest-Ansermet 30, 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, Quai Ernest-Ansermet 30, 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, Quai Ernest-Ansermet 30, 1205 Geneva, Switzerland. Electronic address: michal.borkovec@unige.ch.
authors.forename: Michal
authors.initials: M
authors.lastname: Borkovec
keywords: Atomic force microscope; Colloidal probe technique; Direct force measurement; Multivalent ion; Water-silica interface