Abstract

Detecting cyanide ions (CN−) rapidly and accurately in water is important due to their high toxicity and environmental impact. In this study, we developed a polydopamine stabilized silver nanoparticles (PDA-AgNPs) as a colorimetric probe for the rapid, simple, sensitive and selective determination of CN− ions. The PDA-AgNPs were synthesized and characterized using UV-Vis, TEM, XRD, FT-IR, DLS and Zeta potential measurements. On successive additions of CN− ions, the surface plasmon resonance (SPR) band of PDA-AgNPs at 392 nm was progressively decreased, accompanied by a visible color change from yellow to colorless. This response was attributed to the formation of [Ag(CN)2]− complexes in the presence of oxygen. The method demonstrated a limit of detection to be 0.12 µM. This colorimetric method exhibited an excellent selectivity towards CN− ions detection, over other common interference ions. Further, the proposed assay proved reliable and applicable for real water samples with acceptable recovery percentages. Moreover, to enhance the practical applicability, a smartphone-based detection platform was developed for on-site CN− ion monitoring. © The Author(s), under exclusive licence to Springer Science+Business Media, LLC, part of Springer Nature 2025.