Green synthesis of titanium dioxide nanoparticles using Thymus vulgaris leaf extract for biological applications

In the last few decades, the biosynthesis of nanoparticles using biological agents such as microorganisms or plant extracts has gained a lot of attention due to the growing need for generating safe and non-toxic substances, cost-effective techniques, ecologically friendly solvents, and renewable materials. The aqueous leaf extract of Thymus vulgaris was used in the current investigation to achieve the biosynthesis of TiO2 nanoparticles (TiO2 NPs). In this study, leaf extract was used as a size-reducer in synthesis of TiO2. Thyme leaf extract contains flavonoids, phenols, and saponins, which function as both reducing and stabilising agents and are crucial for the synthesis of TiO2 nanoparticles. Methods such as Fourier-transform infrared spectroscopy (FTIR), ultraviolet-visible diffuse reflectance spectroscopy (UV-DRS), x-ray diffraction (XRD), photoluminescence (PL), and scanning electron microscopy (SEM) with energy dispersive x-ray (EDX) were used to characterise TiO2 NPs. The XRD investigations showed that titanium dioxide nanoparticles are crystalline and average crystal size is 28 nm. Gram-positive bacteria like S. aureus and B. subtilis as well as Gram-negative bacteria like Pseudomonas aeruginosa were used as standardised test microbial inoculums to evaluate the antibacterial properties of biosynthesised nanoparticles (TiO2 NPs). Against each of the studied bacteria, the TiO2 nanoparticles demonstrated significant antimicrobial activity. TiO2 nanoparticles had the maximum activity against Staphylococcus aureus, with an inhibitory zone diameter of 14 mm at 100 g ml−1. By using DPPH, hydroxyl radical techniques, the comprehensive antioxidant activity of produced NPs was examined.