LAUSR

Abstract The present work describes a simple method for the preparation of gold nanoparticles (AuNPs) in aqueous media under ambient conditions and their use in colorimetric detection of Cr (III) and Fe (II) ions. The AuNPs were prepared using methylene blue (MB) as the capping agent and sodium borohydride as the reducing agent in the aqueous medium. The prepared MB-AuNPs were thoroughly characterized using UV–vis spectroscopy, TEM, and FT-IR techniques. The MB-AuNPs were employed as colorimetric for Cr (III) and Fe (II) ions at pH range of 3–8, at room temperature in aqueous solution. In the present of Cr (III) and Fe (II) ions, the MB-AuNPs induces aggregation of the nanoparticles. Upon aggregation, the surface plasmon absorption band red-shifts so that the nanoparticle solution appears a blue color. The MB-AuNPs were found to be highly sensitive to Cr (III) and Fe (II) ions with the detection limit 23.66 and 11.21 nM respectively under optimized conditions in the aqueous medium.