Epitaxial growth of shape-controlled Bi2Te3-Te heterogeneous nanostructures.

A one-pot solution process has been devised to synthesize colloidal Bi2Te3-Te heterogeneous nanostructures (HNs) that comprise Bi2Te3 nanoplates and Te nanorods. By controlling the reaction kinetics, the reaction of TeO3(2-) and Bi(3+) in the presence of hydrazine first produces uniform Te nanorods and then grows Bi2Te3 nanoplates on the tips and surfaces of these Te nanorods, forming various shapes including "nails", "barbells", "syringes", and "accordions". The specific topological arrangement realized arises from the peculiar anisotropic reactivity of the first formed Te nanorods, whose tips are subsequently exploited to seed the heterogeneous nucleation of Bi2Te3 as enabled by the similar crystal structure and the small lattice mismatch between Te and Bi2Te3. Three important processes, heterogeneous nucleation of Bi2Te3 on the tips and/or surface of Te nanorods, homogeneous nucleation of Bi2Te3, and the direct reaction of a Bi precursor and Te nanorods to form hollow structures via the Kirkendall Effect, occur under various conditions. The manipulation of these processes provides a robust means for the fine shape control of Bi2Te3-Te HNs. It is envisioned that the tailored synthesis of Bi2Te3-Te HNs may promise unique opportunities for producing thermoelectric materials with greatly enhanced performance.