A Facile Sunlight‐Induced Synthesis of Phenylalanine‐Conjugated Cholic Acid‐Stabilized Silver and Gold Nanoparticles for Colorimetric Detection of Toxic Hg2+, Cr6+ and Pb2+ Ions.

An efficient and eco‐friendly procedure for the synthesis of highly stable silver (Ag) and gold (Au) nanoparticles (NPs) using phenylalanine conjugated cholic acid (CPhe) in aqueous medium has been developed.These NPs were prepared under natural sunlight irradiation, in which CPhe acts both as self‐reducing and capping agent. The size and shape of the NPs were optimized by changing the ratio of the concentration of CPheand Au3+ ions, pH of the solution, sunlight irradiation and reaction time.The optical properties of the nanoparticles (NPs) were studied using UV‐visible spectroscopy. Size and morphology of the NPs were analyzed using high resolution transmission electron microscopy (HR‐TEM) and dynamic light scattering techniques (DLS) techniques. The interaction of CPhe on the NPs surface were studied by X‐ray photoelectron spectroscopy (XPS) and Fourier transform infrared (FT‐IR) spectra.The synthesized Ag and Au NPs solutions were found to be highly stable for more than a year. The prepared NPs were used as probes for highly selective and sensitive detection of heavy metal ions (Hg2+, Cr6+ and Pb2+) by colorimetric in aqueous medium with a detection limit in the range ofnanomolar concentrations. [ABSTRACT FROM AUTHOR]