Solvent-based dual detection of Hg2+ and Cr3+ ions by polyvinylpyrrolidone stabilized silver nanoparticles as colorimetric sensor

Polyvinylpyrrolidone (PVP)-stabilized silver nanoparticles (PVP–Ag) are utilized for the detection of Hg²⁺ and Cr³⁺ ions by varying the diluting solvents, which alters the material's local surface plasmon resonance (LSPR) absorption band, forming yellow and colorless nanoparticles. Yellow PVP-Ag nanoparticles exhibit an absorption peak at 410 nm. This probe interacts with the Hg²⁺ ions, as a result, the intensity of the absorption peak drops, and the color changes noticeably from yellow to colorless. The colorless transparent PVP-Ag exhibits no absorption peak; however, adding Cr³⁺ ions causes a peak at 440 nm, thus producing a yellow color after the interaction. The TEM, DLS, and FTIR results show the interaction of materials with Hg²⁺ and Cr³⁺, which results in the change of inter-particle distance, leading to the detection of Hg²⁺ and Cr³⁺. The limits of detection (LOD) for Hg²⁺ and Cr³⁺ were determined to be 2.2 nM and 50.9 nM, respectively.