Facile synthesis of silver modified zinc oxide nanocomposite: An efficient visible light active nanomaterial for bacterial inhibition and dye degradation.

The present study reports the synthesis of silver (Ag) decorated zinc oxide (ZnO) nanocomposite via green synthesis method by using Acacia arabica plant leaves extract as both reducing and capping agent. The results clearly indicate a uniform distribution of Ag nanoparticles (NPs) over ZnO surface. Various analytical and spectroscopic techniques were used for investigating the formation and morphology of as-synthesized Ag/ZnO nanocomposites. Emergence of SPR at 424 and 378 nm confirmed the synthesis of AgNPs and ZnO respectively. The confirmation of elemental composition and crystal structure of prepared nanomaterials (NMs) was carried out via EDX and XRD analysis. Results obtained from HRTEM and SEM analysis indicated small sized spherically shaped NMs. The as-synthesized was checked for its photocatalytic activity towards degradation of MB in the presence as well as absence of light irradiation. Results of degradation study revealed that Ag/ZnO exhibits remarkable photocatalytic activity in the presence of light whereby removing 90% of MB within 80 min. Moreover, the antibacterial activity of synthesized nanocomposite was examined in both visible light and dark conditions. The experiment showed that nanomaterial depicts enhanced antibacterial activity in light in comparison to dark. The results showed that the inhibition diameter of Ag/ZnO nanocomposite in light was found to be 18 (±0.2), 22 (±0.3) against E. coli and S. aureus respectively. The inhibition zone of the said nanomaterial against E. coli and S. aureus in dark was 11 (±0.3), 14 (±0.5) respectively. These results conclude that activity is delivered both in the presence of visible light and dark but efficiency of antibacterial activity is found to be more in visible light in comparison.

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

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.