Green Plasmonic Silver Nanoparticles for Colorimetric Sensing of Hg ²⁺ and Fe ³⁺ Ions in Water

ABSTRACT In this study, an eco‐friendly green synthesis method was employed to synthesize silver nanoparticles (AgNPs) using the spinach leaf extract as the reducing and capping agent. The green‐synthesized AgNPs exhibited an effective nanoprobe for the selective colorimetric detection of Fe 3+ and Hg 2+ in water. The synthesized AgNPs were thoroughly examined using several analytical methods, including UV–vis spectroscopy, Fourier transform infrared (FTIR) spectroscopy, high resolution transmission microscopy (HRTEM), Powder X‐ray diffraction (XRD), dynamic light scattering (DLS), and Zeta potential analysis. The AgNPs exhibited a distinct surface plasmon resonance (SPR) band at 440 nm. FTIR of the AgNPs demonstrated the functionalization of the polar leaf extract of spinach leaves. The synthesis of spherical‐shaped AgNPs with an average size of 30 nm and a face‐centered cubic (fcc) geometry was assessed by HRTEM and XRD, respectively. The negative zeta potential of −28.3 mV confirmed colloidal stability. The AgNPs showed high sensitivity for colorimetric detection of Fe 3+ and Hg 2+ with a limit of detection of 158 and 734 ppb, respectively, in spiked water samples, highlighting their potential for use in environmental monitoring applications. Overall, this study presents a simple, cost‐effective, and environmentally benign synthesis of AgNPs with dual functionality as a highly sensitive colorimetric sensor for Fe 3+ and Hg 2+ .