Interaction between solid surfaces in aqueous electrolyte solutions is of great importance to many diverse domains, such as bioMEMS, nanofluidics, colloid science, polymer physics, and molecular biophysics. Several counterintuitive phenomena occur at high concentrations of multivalent ions. In this article, charge reversion, the sign reversal of the effective surface charge in the presence of multivalent counterions, is directly observed through the force between two mica surfaces in aqueous solutions of trivalent cations by surface forces measurements. The effective surface potential functioned with bulk concentration is calculated from an analytical model based on ion correlations. The obtained force profiles can be described by the analytical model when ion correlations effects are taken into account, while Poisson-Boltzmann theory fails. It reveals that ion correlations are important for screening charged surface in the presence of multivalent counterions.

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