Highly Selective Colorimetric Sensor for Cyanide Ions in Water Samples Using Polydopamine-Stabilized Silver Nanoparticles.

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)] 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.