In₂S₃ Micropompons and Their Conversion to In₂O₃ Nanobipyramids:  Simple Synthesis Approaches and Characterization

In 2 S 3 micropompons composed of randomly oriented flakes of ∼10 nm thickness were synthesized in high yield by a facile hydrothermal process. When the product was thermally oxidized at 600 °C, single crystalline well-faceted body-centered cubic (bcc) In 2 O 3 bipyramids of sizes between 50 and 300 nm were obtained. It was proposed that the growth of the In 2 S 3 nanoflakes was initially controlled by the Ostwald ripening process, and finally the aggregation of the flakes led to the development of the micropompons. The growth of the In 2 O 3 bipyramids from the In 2 S 3 micropompons started with the formation of In 2 O 3 nulclei at the surface of the micropompons causing the destruction of the flakelike structure to produce In 2 O 3 bipyramids. The micropompons showed good optical properties due to a strong quantum confinement effect. In 2 O 3 bipyramids showed near-band-edge (NBE) UV emission, which was mainly attributed to the high crystal quality of the bipyramids. The study may provide guidance for the morphology controllable synthesis of different nanostructures and may help in exploring the crystal growth process.