Silver nanoparticles based spectroscopic sensing of eight metal ions in aqueous solutions

Anthropogenic releases from different outlets of industry, municipal sewage and the road traffic can give rise to higher concentrations of heavy metals in food commodities which imposes a threat to human health and environment. A simple silver nanoparticle (Ag NPs) used for the sensing of heavy metal ions, Cd²⁺, Cu²⁺, Fe²⁺, Hg²⁺, Mn²⁺, Ni²⁺, Pb²⁺ and Zn²⁺ in aqueous solution is described qualitatively and quantitatively using spectroscopic tool. FE-SEM and TEM images confirmed that the particles are spherical in shape with an average diameter of 23.4 nm. Presence of heavy metal ions with Ag NPs gives, new peak at around 925, 898, 643, 665, 688, and 838 nm for Cd²⁺, Cu²⁺, Fe²⁺, Hg²⁺, Mn²⁺ and Zn²⁺ in addition to the peak found at 410 nm for Ag NPs. Further, the addition of Ni²⁺ and Pb²⁺ metal ion solution with Ag NPs increased the SPR band from 410 nm to 436 and 462 nm respectively. Citrate functionalized Ag NPs aggregate in solution in the presence of divalent metal ions by ions-template chelating process and are easily measurable changes in the UV-vis absorption spectrum of the particles. Further, studies also confirmed the interaction of Ag NPs with metal ions using FT-IR spectroscopy. The proposed method was found to be useful for simple UV-vis spectroscopic sensing of metal ions in aqueous solutions and real contaminated samples.