Iron oxide tube-in-tube nanostructures

Single-crystalline hematite tube-in-tube nanostructures were prepared by a facile one-step hydrothermal method. The structure, shape, and formation mechanism of the tube-in-tube nanostructures were investigated. The results disclosed that the hematite tube-in-tube nanostructures were formed through a multisite dissolution process of the ellipsoid precursors. What is more, the tube-in-tube nanostructure is a single crystal in nature, and a simple combination of a small tube filling into a big one can be excluded. Single-crystalline magnetite and maghemite tube-in-tube nanostructures were also obtained via a simple reduction or reduction and reoxidation process with the hematite as the precursor. The facile and mild reaction route could be useful for the fabrication of complex tubular nanostructures.