(27b) Synthesis and Characterization of Fe Doped TiO2 Nanomaterials in scCO2 I

TiO2 nanomaterials have received great interest for solar energy applications due to their favorable opto-electronic properties, high chemical stability, and low cost. However, due to their high band gap energy (3.2 eV for anatase) only a small fraction of the solar spectrum can be utilized by TiO2 materials. Therefore, it is highly desirable to engineer the electronic structure by doping transition metal ions into the TiO2 matrix to increase solar energy absorption into the visible region. In this project, mesoporous, high surface area and highly crystalline iron doped TiO2 nanomaterials were synthesized by a modified sol?gel method in supercritical carbon dioxide (scCO2). This route has allowed us to synthesize novel metal oxide nanostructures such as nanospheres, nanofibers and nanotubes. The prepared powders clacined at 500 deg C had a crystallite size ca. 5?15 nm with specific surface area 126 m2/g, which was considerably higher than undoped TiO2 (65 m2/g). BET analysis also revealed that the small amounts of iron increased the specific surface area (SSA) and preserved it through heat treatment, compared to bare titania. UV-Vis spectra showed that the synthesized nanomaterials absorpted spectra in the visible region. These Fe doped TiO2 nanomaterials with the above mentioned characteristics are highly desirable and promising for chemical and energy related applications such as photocatalysts, self cleaning coatings and semiconductors for solar cells. This is a simple, surfactant free, promising synthesis route for producing high surface area, nanocrystallites, mesoporous, nanostructured materials under mild conditions. In addition, this process is very easy to scale up for industrial application. Moreover, replacing organic solvents by the green solvent scCO2 makes this synthesis route both an attractive and promising green process.