Computational (DFT) and experimental analysis of green-synthesized TiO₂ NPs: Characterizations and sustainable approach for photocatalytic and biomedical applications

The biosynthesis of titanium dioxide nanoparticles (TiO 2 NPs) was performed using Persicaria maculosa ( P. maculosa ) and Croton bonplandianum ( C. bonplandianum ) extracts as a natural precursor material, and their physicochemical, photocatalytic and biological properties were studied systematically. The X-ray diffraction analysis confirms the presence of the anatase tetragonal phase, and TiO 2 of P. maculosa - was more crystalline (82.97%) than C. bonplandianum (79.45%). The SEM analysis indicated a smaller size of P. maculosa (20.75 nm) than that of C. bonplandianum (23.01 nm) particle. The UV-Vis analysis showed that the experimental band gaps are 3.041 eV ( P. maculosa ) and 3.054 eV ( C. bonplandianum ). These values demonstratedreasonable qualitative agreement with DFTB+ calculated band, gaps of 3.214 eV and 3.211 eV, with absolute deviations of 0.173 eV and 0.157 eV, respectively. Low-frequency dielectric measurements showed that C. bonplandianum has a larger dielectric constant (47.7) and P. maculosa has a smaller dielectric loss (4.7). Photocatalytic testing revealed that P. maculosa -derived TiO 2 (71.68% MB degradation after 120 min) improved on C. bonplandianum (69.98%). Antibacterial tests showed that C. bonplandianum had the best effect on E. coli with P. maculosa doing better with S. aureus. The two NPs had a partial cytotoxic activity with lethal concentration LC50 values of about 150 µg/ml after 24 h. Overall, this study highlights the comparative structure–property relationship of two plant-mediated TiO₂ NPs through combined experimental and computational analysis. In conclusion, both plants extract-mediated TiO 2 NPs demonstrate multifunctional biomedical properties-photocatalytic, antibacterial, and toxicity, highlighting their potential as a eco-friendly NPs for future therapeutic applications.