Bioinspired gold-silver bimetallic nanoparticles from leaf and bark extract of Simarouba glauca and their antibacterial efficacy

This work reports on using leaf and bark extracts from the Simarouba glauca as a natural reducing agent to synthesize gold-silver bimetallic nanoparticles (Ag-Au NPs). The leaf and bark extracts contain phytochemicals such as tannins, flavonoids, and others, confirmed by Fourier transform infrared spectroscopy (FTIR), responsible for the reduction of both Au and Ag ions. The Surface Plasmon Resonance (SPR) bands obtained at 540 and 543 nm, confirmed the formation Au-Ag alloy. The average crystallite size of Au-Ag NPs synthesized using leaf and bark extracts was 29 and 35 nm. TEM images show that the Au-Ag NPs were spherical, square, pentagonal, and hexagonal morphology. The bimetallic nanoparticles were tested against Staphylococcus aureus, Streptococcus mutans, Bacillus subtilis, and gram-negative bacteria Escherichia coli, Proteus vulgaris, and Klebsiella Pneumoniae showed effective zone of inhibition against the test bacteria. Among the two extracts, the leaf extract was found to be an effective reducing agent to form different shapes of bimetallic nanoparticles. The results indicate that Au-Ag NPs have effective antibacterial activity hence, these nanoparticles can be used for the development of antibacterial agents.