Simultaneous Synthesis of Anatase Colloidal and Multiple-branched Rutile TiO2 Nanostructures

Facile synthesis of titanium dioxide (TiO2) nanostructures with controllability over their cystallinity, dimensions, and shape is in demand for diverse optoelectronic applications. Anatase colloidal particles and precipitates of rutile bundles were synthesized simultaneously using HCl catalyzed sol-gel process with titanium tetrachloride as Ti precursor. The crystallinity and the morphology of these two separable TiO2 phases were studied by X-ray diffraction, Raman spectroscopy, and transmission electron microscopy. The results show that by varying HCl concentration during synthesis, dimensions of colloidal anatase can be tuned from spherical particles with a diameter of 2-5 nm to nanorods of dimension of 4 nm (width) X 14 nm (length). The rutile bundles whose size increased with aging time consisted of multiple branches with elongation along c-axis. Both anatase nanorods and rutile bundles can be applied as highly efficient photocatalysts or electron conduits.