Green synthesis of silver-protein (core–shell) nanoparticles using Piper betle L. leaf extract and its ecotoxicological studies on Daphnia magna

A simple and eco-friendly process for the synthesis of silver-protein (core–shell) nanoparticles (NPs) has been developed using the betle, Piper betle L. (Piperaceae) leaf extract. The exposure time played a major role in the control of biosynthesized NPs size and shell thickness on the surface of silver (Ag) NPs. A heightened fluorescence emission peak was recorded in these NPs, indicating the greater shell size of the Ag NPs and the Transmission Electron Microscopy (TEM) analysis showed their spherical shape. Selected area electron diffraction (SAED) and X-ray diffraction (XRD) results confirmed the presence of nano-crystalline Ag particles. Fourier transform infrared spectroscopy (FTIR) and X-ray photoelectron spectroscopy (XPS) measurements were carried out to identify the proteins that bound specifically on the Ag surface, which increased the stability of the particles. These biogenic Ag NPs were evaluated for their acute toxicity studies against aquatic organism, Daphnia magna and comparisons between the toxicities of the biosynthesized and chemical synthesized Ag NPs were made. The P. betle leaf extracts performed their role as excellent reducing agents of Ag ions and the biosynthesized Ag NPs were also less toxic to D. magna than the chemically synthesized Ag NPs. We presume that the presence of protein shell on the biosynthesized Ag core has decreased the toxic symptoms to the D. magna. It is concluded, apart from being superior over chemical synthesized NPs, the biogenic NPs are safer to the environment as they are less toxic to non-target organisms.