摘要
We investigate the effects of a foreign substance, silica (SiO 2 ), on surface chemistry of commercial titania (TiO 2 ) nanopowder and its chemical interactions with dispersants. The surface of as-received TiO 2 is covered with a 2-3-nm-thick layer of SiO 2 , which gives the nanopowder a low isoelectric point and makes it acidic. Treating the surface with an acidic solution thins the SiO 2 layer to less than 0.5 nm, which allows the TiO 2 nanoparticles to exhibit surface properties similar to uncoated TiO 2 nanoparticles. This variation of surface property of TiO 2 due to acid-treatments results in a great impact on its interactions with dispersants. For as-received TiO 2 nanoparticles, no competitive adsorption is observed between the acidic dispersant, oleic acid (OA), and the alkaline dispersant, oleylamine (OLA). However, for acid-treated TiO 2 nanoparticles, OA competes readily with the adsorption of OLA. © 2011 Elsevier B.V. All rights reserved.