Biosynthesis of ZnO-TiO2 nanocomposites using Azadirachta indica and Ocimum tenuiflorum extract: A comparative study of their microstructural, antibacterial, and photocatalytic properties

Biosynthesized nanocomposites are promising biological agents having economic feasible and eco-friendly uses without any toxic chemicals. The present study was designed to synthesis ZnO-TiO 2 nanocomposites by without green extract (ZT), with neem (ZTN), and tulsi (ZTT) extracts for structural characterization, antibacterial, and photocatalytic activities. ZnO-TiO 2 nanocomposites synthesis were performed by biological method, with a basic pH of 10. Antibacterial activity was evaluated by agar well diffusion methods. The photocatalytic degradation of methylene blue (MB) dye was employed to assess the light-driven catalytic capabilities of the nanocomposites. The formation of wurtzite ZnO hexagonal, anatase TiO 2, and ZnTiO 3 hexagonal phases was confirmed by X-ray Diffraction (XRD) analysis, with average crystallite sizes of 22.52 nm (ZT), 16.92 nm (ZTN), and 19.24 nm (ZTT). Scanning Electron Microscopy (SEM) analysis revealed particle size distributions of 40.75 nm for ZT, 24.94 nm for ZTN NCs, and 26.50 nm for ZTT NCs, while Energy Dispersive X-ray (EDX) validated Zn, Ti, and O presence without any impurity. The UV–vis spectroscopy showed a wider optical band gap energy of 3.48 eV for ZTN NCs compared to 3.40 eV for ZTT NCs and 3.37 eV for ZT NCs. In case of antibacterial activity, ZnO-TiO 2 nanocomposites showed significant inhibition zone with 18.40 mm and 22.50 mm against Staphylococcus aureus (S. aureus) , and Escherichia coli ( E. coli ). The addition of green extracts increased the band gap and transparency of the NCs while reducing their absorption coefficient. Under UV irradiation, ZTN NCs achieved a maximum degradation efficiency of 90.37% within 120 min, substantially higher than those of their counterparts, 82.29% for ZT and 84.45% for ZTT NCs. Overall, the findings showed successfully synthesis, and characteristics of ZnO-TiO₂ nanoparticles to allow its applications in antibacterial and photocatalytic potency. The nanoparticles may helpful for potential biomedical candidates in near future.