Epitaxial Growth of Shape-Controlled Bi_2Te_3-Te Heterogeneous Nanostructures

摘要

A one-pot solution process has been devised to synthesize colloidal Bi_2Te_3-Te heterogeneous nanostructures (HNs) that comprise Bi_2Te_3 nanoplates and Te nanorods. By controlling the reaction kinetics, the reaction of TeO_3~(2-) and Bi~(3+) in the presence of hydrazine first produces uniform Te nanorods and then grows Bi_2Te_3 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 Bi_2Te_3 as enabled by the similar crystal structure and the small lattice mismatch between Te and Bi_2Te_3. Three important processes, heterogeneous nucleation of Bi_2Te_3 on the tips and/or surface of Te nanorods, homogeneous nucleation of Bi_2Te_3, 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 Bi_2Te_3-Te HNs. It is envisioned that the tailored synthesis of Bi_2Te_3-Te HNs may promise unique opportunities for producing thermoelectric materials with greatly enhanced performance.