XPS study of the surfactant film adsorbed onto growing titania nanoparticles

TiO2 particles, prepared by following a sol-gel preparative route, were submitted to hydrothermal growing stages in the presence of an anionic surfactant, sodium dodecyl-sulfate (SDS), at solution pH values corresponding, respectively, to positive surface charges and to the isoelectric point of the oxide. The concentration of the surfactant in the aqueous solution was varied in order to produce different conditions of self-aggregation between the amphiphilic molecules. XPS analyses were performed on the aged and dried precursors to characterize the surfactant films adsorbed onto the oxide. The regions of Ti 2p, O 1s, and C 1s were specifically investigated. The samples, calcined at 600 °C, were characterized for phase composition-crystallinity, by X-ray diffraction, and for surface area. The role played by the oxide-surfactant interactions and by the surfactant self-aggregation phenomena in affecting the physico-chemical properties of the powders is discussed.