Phoenix dactylifera L. extract: antioxidant activity and its application for green biosynthesis of Ag nanoparticles as a recyclable nanocatalyst for 4‑nitrophenol reduction

Abstract

In this study, antioxidant activity as well as preparation of silver nanoparticles (Ag NPs) were investigated by spathe of Phoenix dactylifera L. extracts. Excellent antiradical activity was found for the methanolic extract. Also, catalytic activity of the bio-synthesized Ag NPs was evaluated in the presence of DPPH. Ag nanoparticles were bio-synthesized through an environmental friendly and cost-effective method using aqueous solution of P. dactylifera L. extract. The bio-synthesized Ag NPs were characterized by different techniques including Fourier transform infrared spectroscopy, ultraviolet–visible spectroscopy, transmission electron microscopy, X-ray diffraction, energy-dispersive X-ray spectroscopy, and dynamic light scattering. Then, we focused on optimization of the reaction parameters including pH, AgNO3 concentration, interaction time, temperature and mixing ratio on the bio-synthesis of Ag NPs according to surface plasmon band for Ag NPs around λ = 425 nm. Finally, catalytic ability of the NPs was investigated toward reduction of 4-nitrophenol in the presence of NaBH4, as a model reaction, the results indicated excellent catalytic ability of the NPs for the reduction of 4-nitrophenol for short reaction time. The bio-synthesized Ag NPs demonstrated well recyclability toward 4-nitrophenol reduction without any significant reactivity loss. The recovered NPs were studied by some analytical and spectroscopic methods.