On the Entangled Growth of NaTaO 3 Cubes and Na 2 Ti 3 O 7 Wires in Sodium Hydroxide Solution

• Published in: Chemistry : a European journal 2013-07, Vol.19 (31), p.10235-10243
• Main Authors: Baumann, Stefan O., Liu, Chang, Elser, Michael J., Sternig, Andreas, Siedl, Nicolas, Berger, Thomas, Diwald, Oliver
• Format: Article
• Language: English
• ISSN: 0947-6539; 1521-3765
• DOI: 10.1002/chem.201204281

The entangled growth of sodium titanate Na 2 Ti 3 O 7 nanowires and sodium tantalate NaTaO 3 cubes was investigated with electron microscopy, X‐ray diffraction, and UV diffuse reflectance spectroscopy. Depending on the composition of the Ta 2 O 5 ‐ and TiO 2 ‐particle‐based powder mixtures, which served as educts, we observed different types of hybridization effects. These include the titanium‐induced contraction of the NaTaO 3 perovskite‐type unit cell and the generation of electronic defect states in NaTaO 3 that give rise to optical subbandgap transitions and tantalum‐induced limitations of the Na 2 Ti 3 O 7 nanowire growth. The transformation from Ta 2 O 5 to NaTaO 3 occurs through a dissolution–recrystallization process. A systematic analysis of the impact of different titanium sources on NaTaO 3 dispersion and, thus, on the properties of the entangled nanostructures revealed that a perfect intermixture of cubes and nanowires can only be achieved when titanate nanosheets emerge during transformation as reaction intermediates and shield nucleation and growth of isolated NaTaO 3 cubes. The here demonstrated approach can be highly instrumental for understanding the nucleation and growth of composite and entangled nanostructures in solution and—at the same time—provides an interesting new class of photoactive composite materials.