title: Electrophoretic mobility and charge inversion of a colloidal particle studied by single-colloid electrophoresis and molecular dynamics simulations.
abstract: Optical Tweezers are employed to study the electrophoretic and the electroosmotic motion of a single colloid immersed in electrolyte solutions of ion concentrations between 10(-5) and 1 mol/l and of different valencies (KCl, CaCl(2), LaCl(3)). The measured particle mobility in monovalent salt is found to be in agreement with computations combining primitive model molecular dynamics simulations of the ionic double layer with the standard electrokinetic model. Mobility reversal of a single colloid-for the first time-is observed in the presence of trivalent ions (LaCl(3)) at ionic strengths larger than 10(-2) mol/l. In this case, our numerical model is in a quantitative agreement with the experiment only when ion specific attractive forces are added to the primitive model, demonstrating that at low colloidal charge densities, ion correlation effects alone do not suffice to produce mobility reversal.
authors.affiliation: Institute of Experimental Physics I, Leipzig University, Linnéstrasse 5, D-04103 Leipzig, Germany.
authors.forename: Ilya
authors.initials: I
authors.lastname: Semenov
authors.forename: Shervin
authors.initials: S
authors.lastname: Raafatnia
authors.forename: Marcello
authors.initials: M
authors.lastname: Sega
authors.forename: Vladimir
authors.initials: V
authors.lastname: Lobaskin
authors.forename: Christian
authors.initials: C
authors.lastname: Holm
authors.forename: Friedrich
authors.initials: F
authors.lastname: Kremer
mesh_terms: D003102:Colloids / Q000737:chemistry*; D003198:Computer Simulation; D004586:Electrophoresis / Q000379:methods*; D008956:Models, Chemical; D008958:Models, Molecular; D056004:Molecular Dynamics Simulation; D009038:Motion; D052898:Optical Tweezers; D012212:Rheology / Q000379:methods*; D055672:Static Electricity
chemical_list: D003102:Colloids