Comparative Sol–Hydro(Solvo)thermal Synthesis of TiO2 Nanocrystals

Three small inorganic compounds [acetic acid (CH3COOH), nitric acid (HNO3), and hydrochloric acid (HCl)] andfive small organic compounds [n‐butyl alcohol (CH3CH2CH2CH2OH), 1,2‐propanediol (CH2OHCHOHCH3), 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 °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). (© Wiley‐VCH Verlag GmbH & Co. KGaA, 69451 Weinheim, Germany, 2006)