Green synthesis of silver and gold nanoparticles using Stemona tuberosa Lour and screening for their catalytic activity in the degradation of toxic chemicals

In the present study, silver and gold nanoparticles (AgNPs and AuNPs) were green synthesised using the aqueous plant extract of Stemona tuberosa Lour. When plant extract was mixed with AgNO3 and HAuCl4 solutions in separate reactions, the amalgamated solutions turned deep reddish brown and dark purple in colour after 48h indicating the formation of AgNPs and AuNPs. UV-Visible analysis of green synthesised AgNPs and AuNPs have shown absorption maximum at 443.85nm and 539.72 respectively after 48h. Energy dispersive X-ray spectroscopy (EDX) analysis confirmed the presence of pure silver in the green synthesised AgNPs and pure gold in the plant-mediated AuNPs. X-ray diffractometer (XRD) data revealed the face-centred cubic nature of AgNPs. Fluorescence transmission infrared (FTIR) spectrum has shown the characteristic peaks of different phytochemicals in the plant extract which acted as stabilising or capping agents of AgNPs. Scanning electron microscopy (SEM) analysis of AgNPs and AuNPs revealed that the nanoparticles are monodispersed. Transmission electron microscopy (TEM) studies revealed that AgNPs were mostly spherical with an average size of 25nm whereas selected area electron diffraction (SAED) analysis confirmed their crystalline nature. Both AgNPs and AuNPs of S. tuberosa Lour have shown potential catalytic activity in the presence of sodium borohydride (NaBH4) in the degradation and removal of 4-nitrophenol, methylene blue, methyl orange and methyl red.