Green biomimetic synthesis of Ag-TiO2 nanocomposite using Origanum majorana leaf extract under sonication and their biological activities

Background: Studies of plant extract-mediated synthesis of nanoparticles is extensively explored and studied in recent time due to eco-friendly, cost-effectiveness and minimal use of toxic chemicals for synthesis. In this study, the synthesis of Ag-TiO2 nanocomposites (NCs) was carried out using Origanum majorana leaf extract under ultrasound irradiation. Origanum majorana leaf extract plays an important role as reducing and capping agent in synthesis of Ag-TiO2 nanocomposites (NCs). The antimicrobial activities of synthesised Ag-TiO2 NCs have been studied against Gram-positive and Gram-negative bacteria. In addition to this, the antioxidant activity of green Ag-TiO2 NCs was also evaluated on the basis of free radical scavenging activity against 1,1-diphenyl-2-picrylhydrazyl (DPPH), 2,2 '-azino-bis(3-ethylbenzthiazoline-6-sulfonic acid (ABTS), and hydrogen peroxide free radicals. Results: Green-synthesised Ag-TiO2 NCs were successfully characterised on the basis of UV-Vis spectrophotometer, Fourier transform infrared (FT-IR) spectroscopy, X-ray diffraction analysis (XRD), scanning electron microscopy energy-dispersive X-ray spectroscopy (SEM-EDS) and transmission electron microscopy (TEM). The results revealed the spherical shape of nanocomposite with an average size 25-50 nm. The synthesised Ag-TiO2 NCs have showed significant antimicrobial activity against Escherichia coli, Bacillus subtilis and Aspergillus niger in comparison to TiO2 nanoparticles (NPs). The antioxidant evaluation of biomimetic synthesised Ag-TiO2 NCs also exhibited strong activity than TiO2 NPs and comparable to standard. Conclusion: Green-synthesized Ag-TiO2 NCs provide a promising approach that can satisfy the requirement of large-scale industrial production bearing the advantage of low cost, eco-friendly and reproducible.