Enhancing α-Bi2O3 nanoparticle crystallinity and antibacterial functionality through controlled calcination

Abstract

This study examines the effect of calcination temperature on the structural, vibrational, magnetic, and antibacterial properties of α-Bi₂O₃ pellets synthesized at 300, 400, and 500 °C. XRD analysis confirmed the formation of a single-phase monoclinic α-Bi₂O₃ structure (JCPDS No. 71-0465) for all samples, with enhanced crystallinity at higher temperatures, evidenced by reduced FWHM, increased crystallite size (267.83 to 373.65 nm), and decreased micro-strain and dislocation density. FTIR spectra showed characteristic Bi–O vibrational modes with increased sharpness and intensity at elevated calcination temperatures, indicating improved structural ordering. VSM measurements for the sample calcined at 500 °C revealed weak ferromagnetic behavior with soft magnetic characteristics, exhibiting low coercivity (~150), small remanent magnetization (~0.020 emu g⁻¹), and a maximum magnetization of ~0.060 emu g⁻¹, attributed to defect- and surface-induced magnetism. Antibacterial studies against E. coli and S. aureus demonstrated enhanced efficacy at 500 °C, particularly against E. coli, confirming that higher calcination temperatures significantly improve the multifunctional performance of α-Bi₂O₃.