Structure-property relationships in α-Bi2O3: Correlating synthesis parameters with antimicrobial efficacy against bacterial pathogens

Abstract

Antimicrobial resistance to conventional antibiotics represents a major global health challenge, driving the search for alternative antimicrobial agents. Metal oxides are promising candidates due to their multi-target antibacterial mechanisms and reduced susceptibility to resistance development. However, their overall efficacy and safety profiles often remain inferior to those of conventional small-molecule antimicrobials. Therefore, exploring new metal oxides may yield antibacterial materials with improved performance compared with widely studied systems such as zinc oxide, titania, ceria, and iron oxides. In this study, alpha-Bi2O3 particles are synthesized by thermal decomposition and reverse coprecipitation at different temperatures to investigate the influence of synthesis parameters on structural, morphological, and antibacterial properties. The obtained materials are characterized using X-ray powder diffraction (XRPD), Fourier-transform infrared spectroscopy (FTIR), scanning and transmission electron microscopy (SEM/TEM), and zeta potential analysis. Antibacterial activity is evaluated against the Gram-negative bacterium Escherichia coli and the Gram-positive bacterium Staphylococcus aureus. The results confirm the formation of monoclinic alpha-Bi2O3, with crystallite size and phase purity increasing with synthesis temperature. The synthesis route significantly influences particle morphology, producing smaller particles by thermal decomposition and larger rod-like structures by reverse coprecipitation. All samples exhibit strong antibacterial activity against Escherichia coli, achieving more than 80% growth inhibition within 4 h, whereas Staphylococcus aureus shows higher resistance due to its thicker cell wall structure. The novelty of this work lies in establishing a clear correlation between synthesis parameters, structural characteristics, and antibacterial performance of alpha-Bi2O3 particles, providing new insights for optimizing bismuth oxide-based antimicrobial materials for biomedical applications.