Synthesis and growth mechanism of Bi2S3 nanoribbons

This article describes a facile solvothermal method by using mixed solvents for the large-scale synthesis of Bi2S3 nanoribbons with lengths of up to several millimeters. These nanoribbons were formed by a solvothermal reaction between Bi-III-glycerol complexes and various sulfur sources in a mixed solution of aqueous NaOH and glycerol. HRTEM (high-resolution transmission electron microscopy) and SAED (selective-area electron diffraction) studies show that the as-synthesized nanoribbons had predominately grown along the [001] direction. The Bi2S3 nanoribbons prepared by the use of different sulfur sources have a common formation process: the initial formation of NaBiS2 polycrystals, which serve as the precursors to Bi2S3, the decomposition of NaBiS2, and the formation of Bi2S3 seeds in the solution through a homogeneous nucleation process; the growth of Bi2S3 nanoribbons occurs at the expense of NaBiS2 materials. The growth mechanism of millimeter-scale nanoribbons involves a special solid-solution-solid transformation as well as an Ostwald ripening process. Some crucial factors affect nanoribbon growth, such as, solvothermal temperature, volume ratio of glycerol to water, and the concentration of NaOH; these have also been discussed.