Plasmonic Nano Silver: An Efficient Colorimetric Sensor for the Selective Detection of Hg²⁺ Ions in Real Samples

Environmental pollution caused by heavy metal ions has become a major health problem across the world. In this study, a selective colorimetric sensor based on starch functionalized silver nanoparticles (St-Ag NPs) for rapid detection of Hg²⁺ in real samples was developed. The environmentally friendly green approach was utilized to synthesize starch functionalized silver nanoparticles (St-AgNPs). A multi-technique approach involving UV-Vis absorption spectroscopy, Fourier transform infrared (FT-IR), X-ray diffraction (XRD), and scanning electron microscope (SEM) was used for the characterization of St-Ag NPs. These starch functionalized AgNPs were tested for the detection of heavy metals at 25^◦C. The screening process revealed clear changes in the AgNPs color and absorption intensity only in the presence of Hg²⁺ due to the redox reaction between Ag⁰ and Hg²⁺. The color and absorption intensity of nanoparticles remain unchanged in the presence of all the other tested metals ion. The proposed method has strong selectivity and sensitivity to Hg²⁺ ions, with a detection limit of 1 ppm revealed by UV-visible spectrophotometry. The proposed procedure was found to be successful for the detection of Hg²⁺ in real samples of tap water.