Manipulating the size and morphology of aluminum hydrous oxide nanoparticles by soft-chemistry approaches

We demonstrate control of the size and morphology of aluminum hydrate nanoparticles synthesized by a hydrothermal reaction through manipulating the pH value of the reaction mixture, hydrothermal temperature and the surfactant used. Porous laths were formed under acidic conditions, while the lath-width increased with temperature resulting in the formation of single-crystal porous laths. At neutral or high pH values, porous plates of several nanometers thick were obtained. The pore sizes on both laths and plates were ∼2-3 nm. Stringy lath-shaped nanoparticles were obtained with polyethylene glycol surfactant. The control nanoparticle size and morphology using soft chemical methods is demonstrated. Furthermore, these nanoparticles transformed to γ-alumina nanocrystallites after heating to 673 K, and retained the morphology of the parent boehmite. A detailed characterization of the nanoparticulates and discussion of the mechanism of their formation and subsequent transformation is provided.