The critical role of solvation forces in dispersing and stabilizing nanoparticles and colloids in 1-butyl-3-methylimidazolium tetrafluoroborate [C4mim][BF4] is demonstrated. Stable silica nanoparticle suspensions over 60 wt % solids are achieved by particle surface chemical functionalization with a fluorinated alcohol. A combination of techniques including rheology, dynamic light scattering (DLS), transmission electron microscopy (TEM), and small angle neutron scattering (SANS) are employed to determine the mechanism of colloidal stability. Solvation layers of ∼5 nm at room temperature are measured by multiple techniques and are thought to be initiated by hydrogen bonds between the anion [BF4](-) and the fluorinated group on the surface coating. Inducing structured solvation layering at particle surfaces through hydrogen bonding is demonstrated as a method to stabilize particles in ionic liquids.
Keywords: dispersion stability; ionic liquids; nanoparticles; rheology; solvation layers.