Toward a Low-Temperature Sol−Gel Synthesis of TiO₂(B) Using Mixtures of Surfactants and Ionic Liquids

An approach toward the synthesis of nanocrystalline TiO 2 (B) in surfactant/ionic liquid systems at low temperature (100 °C) by means of sol−gel chemistry is presented. As reaction medium, a solution of imidazolium- and ammonium-based surfactants in ionic liquids was applied. Interestingly, TiO 2 (B), in coexistence with anatase, was observed only in cases where the ionic liquid is based on imidazolium moieties. The final product contained up to 60 wt % TiO 2 (B), depending on the initial amount of surfactant. X-ray powder diffraction measurements and transmission electron microscopy revealed small particle sizes (ca. 2 nm for TiO 2 (B), around 6 nm for anatase) as well as a high crystallinity of the material. The materials possessed surface areas up to 300 m 2 /g. Electrochemical studies further confirmed the presence of the two titania polymorphs anatase and TiO 2 (B) in similar proportions. Small-angle X-ray scattering experiments gave insight into the phase behavior of the surfactant in the ionic liquid under reaction conditions. The formation of TiO 2 (B) is discussed based on systematic variation of diverse parameters.