Comparative sol-hydro(solvo)thermal synthesis of TiO2 nanocrystals

Three small inorganic compounds [acetic acid (CH3COOH), nitric acid (HNO3) and hydrochloric acid (HCI)] and five small organic compounds [n-butyl alcohol (CH3CH2CH2CH2OH), 1,2-propanediol (CH2OHCHOH-CH3), propane-1,3-dicarboxylic acid (HOOCCH2COOH), butane-1,4-dicarboxylic acid (HOOCCH2CH2COOH), and ethylenediamine (H2NCH2CH2NH2)] with different donors (Cl-, NO3-, OH, COO-, and NH2) are used respectively and comparatively in different reaction media for tailoring the sol-hydrothermal synthesis of TiO2 nanocrystals at a specific reaction temperature and/or for different reaction times. Both anatase and rutile with a variety of nanostructures such as nanocubes, nanorods, nanoneedles, and their self-assembled nanospheres are selectively grown. Well-defined and crystalline anatase nanocrystals with a narrow size distribution are prepared in the presence of n-butyl alcohol. With the use of HCL nanoneedles and their assembled nanospheres of phase-pure rutile are obtained under much less drastic conditions, even at 100 degrees C and for only two hours. The effects of the reaction media, synthesis temperatures, and aging times on the structures and shapes of the products are investigated in detail by powder X-ray diffraction (XRD), scanning electron microscopy (SEM), and transmission electron microscopy (TEM).