Effect of Cobalt Doped and Cobalt-Yttrium Co-doped TiO<sub>2</sub> Particles Using Lagenaria siceraria (Molina) Peel Extract via Green Route for Enhanced Photocatalytic and Antibacterial Performance

The paper displays the synthesis and the overall analysis of pure TiO2, Co-doped TiO2 and Co-Y co-doped TiO2 nanoparticles with a keen focus on their structural attributes, optical, photocatalytic and antibacterial characteristics. The tetragonal anatase phase had been confirmed by X-ray diffraction (XRD) and doping did not induce any secondary phases, but it produced the shifting of the peaks and variation of the intensities. Using the Debye-Scherrer and Williamson-Hall methods to determine crystallite size showed that the size decreases as well as a compressive strain accumulates with the increase of dopants concentration. The UV-Vis spectroscopy revealed that the absorption edge and band-gap narrowing changes at 3.12 eV (pure TiO2) to 2.80 eV (1% Co -TiO2) and 2.67 eV (3% Co -Y -TiO2) and the photo-response extension in the visible regime. The presence of co, Y, and TiO2 in 3 percent exhibited better results than the pure TiO2, with 97.48 percent of methylene blue degraded in 120 minutes. Additional antibacterial testing showed that the largest inhibition areas were also at higher concentrations and MIC 25 -40 µg/mL with co-doped samples showing the best activity in Escherichia coli and Staphylococcus aureus. These findings underscore the prospects of Co -Y co-doped TiO2 as a versatile material in the area of environmental remediation and biomedical uses.