The emergence of antibiotic-resistant bacteria and the contamination of water by synthetic dyes represent serious environmental and public health concerns. To address these issues, titanium dioxide (TiO₂) nanoparticles were synthesized through a green approach using Eucalyptus plant extract as a natural reducing and stabilizing agent. This eco-friendly method minimizes the use of hazardous chemicals and offers a sustainable route for nanoparticle production. The biosynthesized amorphous TiO₂ nanoparticles were calcined at different temperatures and characterized using standard techniques to confirm their structural, morphological, and optical properties.

Antibacterial activity was tested against both Gram-positive (Staphylococcus aureus) and Gram-negative bacteria (Escherichia coli) using a 96-well microdilution assay to determine the minimum inhibitory concentration (MIC). In parallel, photocatalytic efficiency was evaluated by monitoring methylene blue (MB) degradation under UV light irradiation. A comparative study with commercial TiO₂ nanoparticles was also conducted to benchmark the performance of the prepared nanomaterials.

The FTIR study showed the presence of terpenoids and flavonoids considered responsible for the formation and stabilization of titanium dioxide nanoparticles, while the XRD studies revealed the crystalline nature of titanium dioxide nanoparticles.

The results revealed that bio TiO₂ nanoparticles calcined at 450 °C exhibited significantly lower MIC values compared to commercial TiO₂, indicating stronger antibacterial potency. Moreover, enhanced photocatalytic degradation of MB was observed, demonstrating their dual functionality.

These findings confirm the potential of Eucalyptus-mediated TiO₂ nanoparticles as cost-effective, sustainable, and environmentally friendly alternatives for biomedical and wastewater treatment applications.