Morphological control in solvothermal synthesis of titanium oxide

A solvothermal method is described for preparing nanomaterials of titanium oxide with different morphologies. Nanostructures, such as wire, rod, cube, and fiber, were synthesized in mass quantities by controlling either the concentrations of the precursor or growth temperature and introducing different additives in one simple system based on titanium tetroisopropoxide and ethylene glycol. Hydrothermal treatment of the base system produced nanowires with diameters around 40 nm. The addition of ethylenediamine (EDA) to the system inhibited the radial expansion of the nanowires, resulting in nanorods and nanofibers with diameters down to about 2 nm. Increasing the EDA concentration tended to induce mesoscale self-assembly of nanofibers into arrays. The presence of water promoted the formation of nearly spherical nanoparticles with sizes dependent on the EDA concentration. At higher temperatures, the same system yielded well-defined nanobelts or nanocubes. The replacement of EDA by 2,4-pentanedione favored the formation of nanosheets while tetramethylammonium hydroxide appeared to confuse the growth of nanorods, creating a continuous network.