A facile and green strategy for the synthesis of Au, Ag and Au Ag alloy nanoparticles using aerial parts of R. hypocrateriformis extract and their biological evaluation

Abstract A facile and green strategy is reported here to synthesize gold (Au), silver (Ag) and gold–silver (Au–Ag) alloy nanoparticles (NPs) through bio-reduction reactions of aqueous corresponding metal precursors mediated by extracts of aerial parts of R. hypocrateriformis , which act as both reducing and stabilizing agents, under microwave irradiation. UV–vis spectrophotometer, XRD, FT-IR, FESEM/TEM, TGA and EDAX analysis were used to characterize the obtained NPs. The formation of NPs is evident from their surface plasmon resonance peak observed at λ max  = ∼550, 450 and 500 nm for Au, Ag and Au–Ag alloy NPs respectively. XRD pattern revealed that fcc structure, while FT–IR spectra signify the presence of phytochemicals adsorbed on NPs. Such a biofunctionalized NPs were characterized by their weight loss, 30% due to thermal degradation of plant phytochemicals observed in TG analysis. The spherical shape of Au, Ag and Au–Ag alloy NPs (∼10–50 nm) is observed by FE-SEM/TEM images. EDAX analysis confirms the expected elemental composition. Moreover, these NPs showed enhanced antimicrobial, antioxidant, and anticancer activities, though it is more pronounced for Au–Ag alloy NPs, which is due to the combining effect of phytochemicals, Au and Ag metals. Thus, the biosynthesized NPs could be applied as effective growth inhibitors for various biomedical applications.