Nanosheets-based phombohedral in₂O₃ 3D hierarchical microspheres: synthesis, growth mechanism, and optical properties

In this Article, we demonstrate a new synthesis route for the construction of rhombohedral In₂O₃ (rh-ln₂O₃) nanosheets-based three-dimensional flowerlike microspheres (NBFMs). In this route, InOOH NBFMs were first prepared by a convenient and controllable method based on a complex reaction, using InCl₃-4H₂O as the starting material, oxalic acid as the complexing agent, and a mixture of glycerol and water as solvent at 180 °C for 12 h. The rh-ln ₂O₃ NBFMs were then obtained by calcining InOOH NBFMs precursors at 490 °C under ambient pressure. Scanning electron microscopy, X-ray diffraction, energy-dispersive X-ray spectroscopy, infrared spectroscopy, and thermogravimetric analysis were adopted to investigate the evolution process of InOOH precursors, and the chemical reactions at each stage were identified. The Ostwald ripening and anisotropic crystal structure are proposed to account for the formation of InOOH NBFMs on the basis of the evaluation of the time-dependent morphology. Furthermore, the influence of solvent on the morphologies and the photoluminescence properties of the rh-ln₂O ₃ NBFMs were investigated.