Development of α-Bi ₂ O ₃ @Ag Nanocomposite for Photocatalytic, Antibacterial Activity, and Gas Sensor Application

α-Bi 2 O 3 @Ag nanocomposites have been synthesized via the hydrothermal technique and characterized for their use as photocatalysts, antimicrobials, and gas sensors. X-ray diffraction (XRD) characterization proved that both α-Bi 2 O 3 and metallic Ag exist in crystal form, where the corresponding diffraction peaks match the standard values of α-Bi 2 O 3 and Ag. The average crystal size was found to be 47.9 nm, and the lattice strain by Williamson-Hall method indicated to be around 0.18%. From field emission scanning electron microscopy (FESEM), irregular rod-like structures, resembling a ginger root structure, with an average diameter of 146.93 nm were observed. From energy-dispersive spectroscopy (EDS), the presence of Ag in α-Bi 2 O 3 was evidenced with the elemental weight percentage composition of 97.2% and 2.8%, respectively. Photocatalytic performance of the α-Bi 2 O 3 @Ag nano-composite was assessed by methylene blue degradation in natural sunlight, giving 58% degradation in 150 minutes of irradiation with an apparent rate constant of 1.12 × 10 -2 min -1 . The antibacterial efficiency of the synthesized sample was determined by evaluating its activity on Staphylococcus aureus and Escherichia coli bacteria, which exhibited higher antibacterial efficiency on S. aureus with larger inhibition zones depending on the increase in the amount of the nanocomposite. In addition, biofilm inhibition efficiency on the same samples of bacteria was also examined using different concentrations of the nanocomposite. Gas sensors based on the α-Bi 2 O 3 @Ag composite indicated a good sensitivity to NO 2 and H 2 S gases with higher response from 4.82 (at room temperature) to 9.75 (at 250 °C) for NO 2 , and from 4.03 to 15.86 for H 2 S.