Preliminary antibacterial screening of waste-assisted zinc oxide–polyaniline nanocomposites against Bacillus subtilis

The antibacterial efficacy of the floral waste-enriched ZnO-PANI nanocomposites was tested against Bacillus subtilis using the zone of inhibition (ZOI) method. The results demonstrated that the ZnO-PANI nanocomposite exhibited superior antibacterial activity compared to individual ZnO or PANI components. Notably, the nanocomposite with the optimized ZnO-PANI ratio produced the largest zone of inhibition, indicating enhanced antibacterial performance due to the synergistic effect between ZnO's inherent antimicrobial properties and PANI's conductivity. The antibacterial evaluation was conducted as a preliminary screening using a solid-state contact assay, and the observed activity is interpreted qualitatively within this framework. The proposed antibacterial mechanism is based on literature-supported hypotheses rather than direct experimental validation. This study demonstrates the feasibility of waste-assisted nanocomposite fabrication and provides initial insight into its surface-contact antibacterial potential, while acknowledging the need for further quantitative and mechanistic investigations.