一步沉淀法制备三维分等级花状α-Bi₂O₃微球及其光性能

Three-dimensional (3D) hierarchical constructed flower-like α-Bi₂O₃ microspheres were prepared successfully via a simple solution precipita-tion method at 95℃ and ambient atmospheric pressure in 1 h. The synthesis process was operated in an ethanol-water system as solvent with the assistance of glycerol as capping agent. X-ray diffraction (XRD) and field-emission scanning electron microscope (FE-SEM) were employed to characterize the obtained products. The samples were all α phase with diameter of micrometer scale. With different concentration of glycerol, Bi₂O₃ shows different microstructures. When glycerol concentration was low, the product was nanocubes 3D self-assembled hierarchical flower-like microspheres, while at high glycerol concentration, the one-dimensional nanorods self-assembled hierarchical flower-like microspheres were obtained. The formation mechanism of the special micro-morphology was also analyzed. UV-visible diffuse reflectance spectrum shows that the samples present photoabsorption property from UV light region to visible light range, belonging to the absorption caused by electron transition from valence band to conduction band, which is Bi₂O₃ direct band gap absorption. The band gaps of the Bi₂O₃ samples are estimated to be 2.76 eV and 2.70 eV. The fluorescence spectrum of the samples shows broad emission (400-600 nm) and five emission bands (band centers are located at 450 nm, 466 nm, 480 nm, 490 nm, and 562 nm). The waveform and intensity of the fluorescence emission bands were affected by the micro-morphology of the materials. And the fluorescence intensity of nanorods self-assembled hierarchical flower-like microspheres was slightly weaker.