Preparation and characterization of wire-like Sb_2Se_3 and flake-like Bi_2Se_3 nanocrystals

摘要

Crystalline Sb_2Se_3 and Bi_2Se_3 have been prepared through the reaction between SbCl_3 (or BiCl_3) and elemental selenium using sodium sulfite as a reducing reagent. TEM images show that the as-prepared Sb_2Se_3 comprise uniform nanowires, while Bi_2Se_3 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 Sb_2Se_3 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 Sb_2Se_3 and Bi_2Se_3 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 Sb_2Se_3 and flake-like hexagonal Bi_2Se_3 crystals, respectively. These arguments can also be applied to explain the growth behavior of other Ⅴ_2Ⅵ_3-type crystals.