Synthesis, characterization, and electrophoretic concentration of titanium dioxide nanoparticles in AOT microemulsions.

Abstract

Stable organosols of TiO2 nanoparticles were prepared by hydrolysis of titanium tetraisopropoxide (TTIP) in microemulsions of sodium bis(2-ethylhexyl)sulfoxynate (АОТ) in n-decane with increasing the content of aqueous pseudophase from 0.15 to 0.85vol.%. As the water content increased, the hydrodynamic diameter of nanoparticles grew from 10 to 225nm, and the ζ-potential, from -6 to 18mV (the surface of TiO2 nanoparticles was recharged when the water content was 0.45vol.%). Nonaqueous electrophoresis in a capacitor-type cell made it possible to concentrate nanoparticles with a diameter of 60 to 225nm (concentration factor was 10), separate 20nm and 225nm particles, and decrease the content of АОТ in organosol by an order of magnitude. Preparation of a concentrate of nanoparticles with a low content (0.015M) of AOT included the following stages: (i) electrophoresis after synthesis; (ii) sampling of the concentrate and its twenty-fold dilution with pure n-decane; and (iii) repeated electrophoresis. In situ laser and spectrophotometric scanning of the interelectrode space showed the formation of a sharp boundary between the raffinate and the layer of moving nanoparticles during electrophoresis.