A Tagetes minuta based eco-benign synthesis of multifunctional Au/MgO nanocomposite with enhanced photocatalytic, antibacterial and DPPH scavenging activities

Highlights: • An Eco-benign synthesis of novel Au/MgO nanocomposite using leaf extract of Tagetes minuta as reducing and capping agent. • Au/MgO nanocomposite have significant antibacterial activity against multidrug resistant bacteria. • Au/MgO nanocomposite possess efficient antioxidant activity. • Τοxicity against Red blood cells • Au/MgO nanocomposite shown efficient photocatalytic activity in terms of photocatalytic degradation of Methylene Blue. In this research work, facile, economical and eco-benign experimental procedure were adopted to synthesize Au/MgO nanocomposite with the help of Tagetes minuta leaves extract. Phytochemicals present in the leaves of Tagetes minuta were acting as reducing and stabilizing agents to avoid aggregation of nanomaterials during the preparation of Au/MgO nanocomposite. The biologically synthesized nanocomposite were systematically characterized by UV–vis spectroscopy, Scanning electron microscope (SEM), X-ray diffraction (XRD), Fourier transform infrared microscopy (FTIR), High resolution transmission electron microscopy (HRTEM), Thermogravimetric analysis (TGA), dynamic light scattering (DLS) and elemental mapping. UV–visible spectrum confirmed the presence of MgO and Au due to the presence of two SPR peaks at 315 nm and 528 nm, respectively. Moreover, the Au/MgO nanocomposite exhibited superior photocatalytic, antibacterial, hemolytic, and antioxidant activities. Photocatalytic performance tests of Au/MgO nanocomposite were- appraised by the rapid degradation of the methylene blue (MB) under UV light illumination. More importantly, after four successive cycles of MB degradation, the photocatalytic efficacy remained unchanged, which ensures the stability of the Au/MgO nanocomposite. Furthermore, the antibacterial tests showed that the advanced nanocomposite inhibited the growth of Escherichia coli, Bacillus subtilis, and Staphylococcus aureus with zones of inhibition 18 (±0.3), 21 (±0.5), and 19 (±0.4) mm, respectively. The cytotoxicity study revealed that Au/MgO nanocomposite is nontoxic to ordinary healthy RBCs. Interestingly, the Au/MgO nanocomposite also possesses an excellent antioxidant activity, whereby effectively scavenging 82% stable and harmful DPPH. Overall, the present study concludes that eco-benign Au/MgO nanocomposite has excellent potential for the remediation of bacterial pathogens and degradation of MB.