Fluorescent silver nanoclusters as effective probes for highly selective detection of mercury(II) at parts-per-billion levels.

Facile preparation of water-soluble and fluorescent Ag nanoclusters (NCs) stabilized by glutathione at room temperature is described. Although the glutathione layer was introduced to prevent the silver nanoparticles from decomposition and increase their water solubility, this simple surface optimization resulted in surprisingly high efficiency of selective Hg(2+) sensing, where the limit of detection (LOD) was as low as 10(-10)  M (0.02 ppb, 0.1 nM). This result revealed a simple and practical strategy for Hg(2+) detection using fluorescent Ag NCs as sensor probe, with the lowest detecting limits reported to date.