Photocatalytic and antibacterial activities of gold and silver nanoparticles synthesized using biomass of Parkia roxburghii leaf

• Gold and silver nanoparticles were biosynthesized using dried biomass of Parkia roxburghii leaf.
• Powder XRD showed fcc structure of gold and silver with average crystallite size of 8.4 and 14.74 nm.
• TEM images showed gold and silver nanoparticles to be spherical and quasi-spherical of size 5–25 nm.
• The synthesized nanoparticles exhibited pronounced photocatalytic and antibacterial activities.

The present study reports a green approach for synthesis of gold (Au) and silver (Ag) nanoparticles (NPs) using dried biomass of Parkia roxburghii leaf. The biomass of the leaf acts as both reductant as well as stabilizer. The as-synthesized nanoparticles were characterized by time-dependent UV–visible, Fourier transform infrared (FT-IR), powder X-ray diffraction (XRD), and transmission electron microscopy (TEM) analyses. The UV–visible spectra of synthesized Au and Ag NPs showed surface plasmon resonance (SPR) at 555 and 440 nm after 12 h. Powder XRD studies revealed formation of face-centered cubic structure for both Au and Ag NPs with average crystallite size of 8.4 and 14.74 nm, respectively. The TEM image showed the Au NPs to be monodispersed, spherical in shape with sizes in the range of 5–25 nm. On the other hand, Ag NPs were polydispersed, quasi-spherical in shape with sizes in the range of 5–25 nm. Investigation of photocatalytic activities of Au and Ag NPs under solar light illumination reveals that both these particles have pronounced effect on degradation of dyes viz., methylene blue (MB) and rhodamine b (RhB). Antibacterial activity of the synthesized NPs was studied on Gram positive bacteria Staphylococcus aureus and Gram negative bacteria Escherichia coli. Both Au and Ag NPs showed slightly higher activity on S. aureus than on E. coli.

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