Charge renormalization of nanoparticles immersed in a molecular electrolyte.

The renormalization of the electric charge of nanoparticles (small colloids) at infinite dilution immersed in a supporting electrolyte containing molecular ions is studied here using a simple model. The nanoparticles are represented by charged spheres of finite diameter, the anions are assumed to be pointlike, and the cations are modeled as two identical charged points connected by a rigid rod. The static structure of this model system is determined using the reference interaction site model equations with suitable closure relations and the renormalized charges are analyzed employing the dressed interactions site theory approach. It is found that for a wide range of ionic strengths these renormalized charges are clearly dependent on the length of the cations for nanoparticles with negative bare charge, but this dependence is practically negligible for nanoparticles with positive bare charges. In the limit of zero cation length and small nanoparticle charges the standard Derjaguin-Landau-Verwey-Overbeek model renormalization is recovered. A brief account of the structural and thermodynamic properties of the model molecular electrolyte is also provided.