Gas sensing and photocatalytic activity of synthesized hierarchical Bi₂O₃ nanoflakes by sol–gel and nanosheets by hydrothermal method

The research involves synthesizing hierarchical nanoflakes of bismuth oxide (Bi₂O₃) using the sol–gel (SG) method and Bi₂O₃ nanosheets through hydrothermal (HY) synthesis, with a focus on investigating their gas sensing and photocatalytic activity. The synthesized Bi₂O₃ analyzed using X-ray diffraction (XRD) techniques reveals that SG and HY are monoclinic crystal structures. Fourier-transform infrared spectroscopy (FTIR) did the functional group analysis, which shows the absorption band at 874 cm⁻¹ and 858 cm⁻¹ in typical stretching and bending vibrations characteristics. The surface morphology of synthesized Bi₂O₃ material was carried out by field emission scanning electron microscopy (FESEM), which reveals the nanosheet type morphology and one-sided arrangement like a flower by SG and HY synthesis, respectively. The gas sensing activity of Bi₂O₃ thick films was prepared by screen printing technique and examined for different gases such as H₂S, NH₃, LPG, C₂H₅OH, H₂, CH₃OH, CO₂, and Cl₂. They showed highest sensitivity to H₂S against NH₃, LPG, C₂H₅OH, H₂, CH₃OH, CO₂ and Cl₂. The catalyst Bi₂O₃ with methylene blue (MB) dye showed better photocatalytic performance of the SG method than HY synthesis.