We report a size-manipulable synthesis of single-crystalline nanorods/nanowires of barium manganite (BaMnO 3 ) and barium titanium manganite (BaTi 1/2 Mn 1/2 O 3 ) by using the composite-hydroxide-mediated approach. The synthesis cleanly yields nanorods with a hexagonal perovskite structure. Typical nanorods have widths ranging between 50 and 100 nm, and the lengths can be easily controlled by time and temperature or by adding a small amount of water during the synthesis process. Resistance measurement shows that a phase transition happened at 58 K on BaMnO 3 . The photoluminescence spectrum of BaTi 1/2 Mn 1/2 O 3 presents two emission peaks at wavelengths of 465 and 593 nm, corresponding to blue and green fluorescence. The ability to synthesize nanorod manganites of a desired length should enable detailed investigations of the size-dependent evolution of magnetism, magnetoresistance, nanoscale phase separation, and realization of a nanodevice of magnetic sensors.

The influence of water on morphology and structure of nanomaterials synthesized by the composite-hydroxide-mediated (CHM) approach has been systematically investigated. A small amount of water would affect the morphology and size, while a large amount of water would affect not only the morphology, but the structure of nanomaterials. The experimental results indicate that the nanocrystals prefer anisotropic growth and form more regular shape by the CHM route to hydrothermal synthesis.