Structural and optical characterization of TiO2 nanoparticles synthesized using Globularia alypum leaf extract and the antibacterial properties

Abstract

Abstract The biosynthesis of nanoparticles using environmentally friendly routes has gained attention due to the need for safe, non-toxic, and cost-effective methods of nanomaterials synthesis. In the present study, different volumes (10, 20, and 30 mL) of aqueous leaf extract of Globularia alypum (GA) were used to synthesize titanium dioxide (TiO2) nanoparticles (NPs). The synthesized NPs were characterized using multiple analytical techniques, including X-ray diffraction (XRD), ultraviolet–visible spectroscopy (UV–vis), transmission electron microscopy (TEM), and scanning electron microscopy (SEM). XRD results confirmed the rutile phase of TiO2 as well as the crystalline nature and purity of the NPs. UV–Vis spectroscopy showed absorption spanning from the UV to the visible region, with a maximum peak between 325 and 370 nm. The calculated direct band gap energies were 3.40, 3.65, and 3.80 eV for TiO₂(3), TiO₂(2), and TiO₂(1), respectively. Both SEM and TEM indicated spherical nanoparticle morphology across all extract concentrations, with particle sizes increasing in direct proportion to the volume of extract used. Fourier Transform Infrared spectroscopy analysis of GA showed characteristic peaks for various functional groups that mediated the formation of the TiO2 nanoparticles. The antibacterial properties of the biosynthesized TiO₂ NPs were evaluated against multiple clinically relevant Gram-positive and Gram-negative bacterial species. The TiO₂ nanoparticles demonstrated significant antimicrobial activity against all studied bacteria using the standard disc diffusion assay. At the least TiO₂ concentration of 10 µg/mL, highest anatimicrobial activity was observed against typed stains of Escherichia coli and Bacillus cereus, with inhibitory zone diameters of 17 mm and 16 mm, respectively. These results clearly indicate that plant-mediated nanoparticles could be useful for future biological applications, specifically in combating the challenge of drug resistance in clinical microorganisms.

Keywords

• Titanium dioxide
• Green synthesis
• Leaf extract
• Globularia alypum
• Biological assay