Controllable Synthesis of TiO₂ Single Crystals with Tunable Shapes Using Ammonium-Exchanged Titanate Nanowires as Precursors

A novel type of titanium precursor, ammonium-exchanged titanate nanowires, is used to hydrothermally synthesize nanosized TiO 2 single crystals with well-defined facets. With additives of appropriate shape-capping reagents, octahedral, truncated octahedral, and spindle-like TiO 2 nanocrystals have been obtained. We proposed that the transformation mechanism from ammonium-exchanged titanate nanowires to TiO 2 may be a “dissolution−nucleation” process. Furthermore, the photocatalytic activities of anatase TiO 2 nanocrystals with different facets exposed have been investigated.