Growth of Single-Crystal Double-Directional Tellurium Nanoneedles from CdTe Nanocrystals in Solution

Single-crystal double-directional tellurium (Te) nanoneedles were grown by a facile route of air oxidation of CdTe nanocrystals in aqueous solution containing ammonia. The as-synthesized Te nanoneedles with a relatively high yield and uniformity grew along the [001] crystalline direction with lengths of 2−4 μm and stem diameters of 80−120 nm, and gradually becoming thinner to form sharp tips of sub-5 nm. The double-directional nanoneedles were straight, with high purity, well-crystallized, and dislocation-free, according to range of methods such as X-ray powder diffraction, scanning electron microscopy, energy-dispersive X-ray spectroscopy, transmission electron microscopy, high-resolution transmission microscopy, and selected area electron diffraction. The detailed transformation process from CdTe nanocrystals to single-crystal double-directional Te nanoneedles was studied. It is expected that the single-crystal double-directional Te nanoneedles would be a very promising new member of field emitters, probes of atomic force microscopy, and used in the manufacture of functional nanodevices.