A Simple and Fast Colorimetric Assay for the Detection of Chloride Ions Based on Etching of Silver Triangular...

It is of essential importance to precisely detect chloride ions (Cl^-) for environmental monitoring and protection. However, major challenges still remain for reliable, simple, and rapid detection of Cl^-. Herein, we present a simple and rapid colorimetric method for detecting Cl^- by utilizing unmodified silver triangular nanoplates (AgNPrs) as the colorimetric agent. The detection principle is based on the Cl^--induced etching of AgNPrs into round nanodisks, resulting in a blue shift in the absorption peak and an observable color transition from blue to yellow. A good linear relationship between Cl^- concentration and the peak blue shift of absorption spectra is achieved in the range of 140-220 μM, with a naked-eye detection limit of 96 μM. Due to its superior sensitivity and selectivity, the proposed colorimetric sensor is successfully applied for discriminating Cl^- from real water samples. Besides, the colorimetric assay is a valid method for investigating binding sites and the change of Gibbs free energy (ΔG) during the Cl^--induced etching process of AgNPrs.