The influence of the structure of the surface of hydrophilic-hydrophobic silicas on the adsorption of cholic acid

We synthesized hydrophilic-hydrophobic silicas with uniform and island arrangements of functional groups over the surface and various degrees of surface hydrophobicity. The adsorption of cholic acid on hydrophilic-hydrophobic silicas was studied as depending on acid concentration in solution. Adsorption was shown to be largely determined by dispersion interactions between hydrophobic surface regions and steroid cholic acid segments. Enhanced adsorption ability was observed for hydrophilic-hydrophobic silica with a mosaic surface structure. This was caused by the contribution of geometric cholic acid imprints into the total adsorption.