Detection of Ag ions via an anti-aggregation mechanism using unmodified gold nanoparticles in the presence of thiamazole.

The present study proposed a novel and highly selective and sensitive method for Ag ion detection based on gold nanoparticles (AuNPs) anti-aggregation. Thiamazole can induce AuNPs aggregation due to electrostatic interactions, which result in color transitions in the AuNPs solution from red to blue. However, the presence of Ag ions results in the preferential combination of the pyridinic nitrogen of thiamazole with the Ag ions. In addition, the Ag ions oxidize the sulfhydryl groups(-SH), which inhibit AuNPs aggregation and prompt a color change from blue to red. As a result, the present study established a method for Ag ion determination by AuNPs-thiamazole colorimetric probe based on the aforementioned anti-aggregation mechanism. The probe dynamic range was easily tuned via adjustments of the thiamazole amount. The relationship between the Ag concentration and AuNPs aggregation was monitored by ultraviolet-visible light (UV-Vis) spectroscopy at a dynamic range of 0.1 nM-9 μM and at a detection limit of 0.042 nM. The river water and tap water recovery analysis validated the successful operation of this colorimetric sensor in environmental monitoring.