Preparation and characterization of wire-like Sb2Se3 and flake-like Bi2Se3 nanocrystals

Crystalline Sb2Se3 and Bi2Se3 have been prepared through the reaction between SbCl3 (or BiCl3) and elemental selenium using sodium sulfite as a reducing reagent. TEM images show that the as-prepared Sb2Se3 comprise uniform nanowires, while Bi2Se3 crystals exhibit a hexagonal flake-like morphology. The optical absorption of the products has been investigated, and the optical band gap energy for direct transition in Sb2Se3 nanowires is found to be 1.46 eV. The composition of the as-prepared products has been identified by XPS. The reaction mechanism is discussed in detail, and it is proposed that the oriented growth behavior of Sb2Se3 and Bi2Se3 crystals is determined by their cleavage nature. The chain-like arrangement of Sb and Se atoms parallel to the c-axis in the orthorhombic lattice and the two-dimensional assembly of Bi and Se atoms perpendicular to the c-axis in the hexagonal cell contribute to the formation of wire-like Sb2Se3 and flake-like hexagonal Bi2Se3 crystals, respectively. These arguments can also be applied to explain the growth behavior of other V2VI3-type crystals. (C) 2003 Elsevier Science B.V. All rights reserved.