Bifunctionalization of silver nanoparticles with 6-mercaptonicotinic acid and melamine for simultaneous colorimetric sensing of Cr3+ and Ba2+ ions

We describe the applications of bifunctionalized silver nanoparticles (Ag NPs) with 6-mercaptonitotinic acid (MNA) and melamine (MA) for simple, rapid and simultaneous colorimetric detection of Cr3+ and Ba2+ ions in water samples. The bifunctionalized Ag NPs were confirmed by UV-visible, FT-IR, dynamic light scattering (DLS) and transmission electron microscopy (TEM) techniques. The MNA and MA molecules on Ag NPs surfaces allowed to act as selective binding sites for Cr3+ and Ba2+ ions. As a result, these Ag NPs were induced to aggregate quickly with Cr3+ and Ba2+ ions through color change from yellow- to reddish brown (Cr3+) and -to orange (Ba2+), respectively which was readily seen by the naked eye.