Microemulsion-mediated hydrothermal synthesis and characterization of nanosize rutile and anatase particles

Uniform nanoparticles of rutile and anatase were prepared, respectively, by a new approach, a microemulsion-mediated method, in which the microemulsio n medium was further treated by hydrothermal reaction. Herein, the combined procedure of microemulsion and hydrothermal synthesis to prepare nanoparti cles is referred to as a microemulsion-mediated hydrothermal (MMH) method. This MMH method could lead to the formation of crystalline titania powders under much milder reaction conditions than the normally reported microemuls ion-mediated methods, in which posttreatment of calcination was necessary. In this work, a kind of solution was formed by dissolving tetrabutyl titana te into hydrochloric acid or nitric acid, and the solution was dispersed in an organic phase for the preparation of the microemulsion medium. The aque ous cores of water/Triton X-100/hexanol/cyclohexane microemulsions were use d as constrained microreactors for a controlled growth of titania particles under hydrothermal conditions. The product of hydrothermal synthesis was s eparated and dried for characterization. The phase components and the morph ologies and grain sizes of products were determined by X-ray diffraction (X RD) and by transmission electron microscopy (TEM). The effects of changing the variables of the reaction conditions, such as the use of acid, the conc entrations of acid, the reaction temperatures, and/or the reaction times on the phases and morphologies of the titania product are described.