Fig. 5: Cluster formation in aqueous electrolytes containing monovalent and divalent cations.
From: Chemical control of colloidal self-assembly driven by the electrosolvation force
a Digitised experimental image of negatively charged SiO2 colloidal suspensions forming clusters in the presence of LiCl, NaCl, RbCl, CsCl, MgCl2, CaCl2, and BaCl2 at an ionic strength of 0.1 mM. The scale bars represents 20 μm. b Measured \(g(r)\) profiles in each case, with inferred pair interaction potentials \(U(x)\) presented for Cs+ and Ba2+ (inset). Note that at the rather small interparticle separation \(x\approx 0.1\) μm characteristic of these experiments, the estimated attractive contribution to the pair potential from the van der Waals force is \(\approx 1 \, {{{{\rm{k}}}}}_{{{{\rm{B}}}}}T\), which is larger than in the rest of the experiments in the study but significantly smaller than the measured minima of depth \(w\approx 6\) \({{{{\rm{k}}}}}_{{{{\rm{B}}}}}T\).
