Chia-Erh Liu, Annabelle Rouet, Hari Sutrisno, Eric Puzenat, Hélène Terrisse, Luc Brohan, Mireille Richard-Plouet
A low-temperature aqueous chemical growth process was developed to produce nanometric titanium oxide with controlled size and structural variety. Gentle hydrolysis of a commercial TiOCl2 solution, in a controlled relative humidity, leads to the formation of single crystals of [Ti8O 12(H2O)24]Cl8·HCl· 7H2O. Under autogenous pressure at 120 °C, the hydrolysis of the latter by tetramethylammonium hydroxide (noted TMAOH) is mainly governed by the R = Ti/TMAOH molar ratio and thus by the pH value. Two values are particularly important: R = 8/9 and 8/17. The former corresponds to the balance of the Cl- ions of the titanium oxychloride hydrate by TMA+ cations and the latter to the stoichiometric ratio for the formation of a layered oxo-hydroxide (TMA)2Ti2O4-x(CO 3)X(OH)2·nH2O, x = 0.7, which is obtained under basic conditions. Above R = 8/9, that is, in an acidic medium, the solvothermal treatment at 120 °C directly leads to the crystallization of anatase and then rutile when the pH decreases. For intermediate R values, the amorphous dried solid is required to be rinsed and dried at 110 °C to lead to the crystallization of nanometric titania, either anatase or brookite. TEM studies show that titania nanoparticles exhibit superstructures involving a doubling of the cell parameters that could originate from the adsorption of carbonate, hydrogen carbonate, or hydroxyl groups on the nanocrystallite surface. During evaporation of the solvent, these crystallites can self-assemble to form micrometric platelets. © 2008 American Chemical Society.
Institut des Matériaux Jean Rouxel, Université de Nantes, CNRS, 44322 Nantes Cedex, 2, rue de la Houssinière, France; Department of Chemistry, Faculty of Mathematic and Natural Sciences, Yogyakarta State University, Karangmalang, 55281 Yogyakarta, Indonesia; IRCELYON Institut de Recherches sur la Catalyse et l'Environnement de Lyon, UMR 5256 CNRS, Université Lyon, 69629 Villeurbanne Cedex, 2 Avenue Albert Einstein, France
