Phase-pure TiO2 nanoparticles: anatase, brookite and rutile

Abstract

We report on the synthesis of phase-pureTiO2 nanoparticles in anatase, rutile and brookite structures, using amorphous titania as acommon starting material. Phase formation was achieved by hydrothermal treatment atelevated temperatures with the appropriate reactants. Anatase nanoparticles wereobtained using acetic acid, while phase-pure rutile and brookite nanoparticles wereobtained with hydrochloric acid at a different concentration. The nanomaterials werecharacterized using x-ray diffraction, UV–visible reflectance spectroscopy, dynamic lightscattering, and transmission electron microscopy. We propose that anatase formation isdominated by surface energy effects, and that rutile and brookite formation follows adissolution–precipitation mechanism, where chains of sixfold-coordinated titaniumcomplexes arrange into different crystal structures depending on the reactant chemistry.The particle growth kinetics under hydrothermal conditions are determined by coarseningand aggregation–recrystallization processes, allowing control over the average nanoparticlesize.