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.
Ning et al. (Tue,) studied this question.