Green Synthesis of Sodium Cholate Stabilized Silver Nanoparticles: An Effective Colorimetric Sensor for Hg2+ and Pb2+ Ions

In this study, we have reported a facile, cost-effective and green approach for the preparation of AgNPs in aqueous medium using sodium cholate (NaC) as a reducing and stabilizing agent under sunlight exposure. The synthesized AgNPs were thoroughly characterized using UV-visible spectroscopy, Transmission electron microscopy (TEM) and Field emission scanning electron microscopy (FE-SEM) techniques. The anisotropic and spherical shaped NPs were prepared by varying the concentration of NaC from below to above critical micellar concentration (CMC) at neutral pH and showed very good stability for more than one year without any noticeable aggregation. Kinetics of the formation of anisotropic and spherical shaped NPs were monitored using UV-visible spectroscopy. The synthesized AgNPs showed excellent selective towards Hg2+ and Pb2+ ions that could be monitored by UV-visible spectrophotometer and naked eyes, with lowest detection limit (LOD) of 12 and 60 nM for Hg2+ and Pb2+ respectively. The AgNPs embedded in the gel network was confirmed by FE-SEM image. The reported sensor showed rapid and sensitive detection of Hg2+ and Pb2+ ions at nM level in water samples, indicating its potential applicability for detection of the metal ions in real samples such as tap and drinking water.