Thickness of solvation layers on nano-scale silica dispersed in water and ethanol

In this work, the thickness of solvation layers on nano-scale silica dispersed in water, ethanol, and water-ethanol mixture (1: 1 by volume) have been determined with the viscosity method, which is based on the Einstein equation of viscosity of dispersion. This determination was carried out on a nano-scale silica with the specific surface area of 189 m(2)/g through the measurements of relative viscosity of the silica dispersion as the function of volume fraction of the dry silica in the dispersion. The experimental results and the calculations showed that the thickness of the solvation layer on the nano-scale silica was 12.8 nm in water, 11.9 nm in ethanol, and 13.2 nm in the water-ethanol mixture. The results suggest that water-ethanol mixture (1: 1 by volume) should be used as the liquid medium in order to prepare a high stability nano-scale silica suspension.