Structure and optical properties of Bi2S3 and Bi2O3 nanostructures synthesized via thermal evaporation and thermal oxidation routes

Bi2S3 nanorods with diameters of a few tens of nanometers and lengths of a few to a few tens of micrometers were synthesized by thermal evaporation. Subsequently, Bi2O3 nanostructures were synthesized by thermal oxidation of the Bi2S3 nanorods. The structural evolution of the two nanomaterials and their luminescence properties were examined by scanning electron microscopy, transmission electron microscopy, X-ray diffraction, energy-dispersive X-ray spectrometry, and photoluminescence (PL) spectroscopy. The PL measurements revealed the as-synthesized Bi2S3 nanorods to have an emission band centered at ∼595 nm. The Bi2O3 nanorods synthesized by the thermal oxidation of Bi2S3 nanorods for 1 h showed an emission band centered at ∼440 nm, which is in the bluish violet region. In contrast, the Bi2O3 nanostructures synthesized by thermal oxidation of Bi2S3 nanorods for 2 or 3 h showed an emission band centered at ∼505 nm, in the bluish green region, and a shoulder at ∼380 nm. The origins of the emissions are also discussed.