High-Performance Colorimetric Detection of Hg2+ Based on Triangular Silver Nanoprisms

Mercury ion (Hg2+) arising from a variety of natural sources and industrial wastes has been widely recognized as one of the most hazardous pollutants. It is very important to develop highly selective and sensitive probe for rapid detection of Hg2+ in aquatic ecosystems. Here we propose a new strategy for high-performance colorimetric detection of Hg2+, i.e., anti-etching of silver nanoprisms (AgNPRs). In the absence of Hg2+, the AgNPRs can be etched by I– inducing an obvious color change from blue to red. However, in the presence of Hg2+, the formation of Ag–Hg nanoalloy can protect the AgNPRs from I– etching and the color remains blue. This mechanism is verified by UV–vis, TEM, DLS, and EDS. Our AgNPRs-based colorimetric probe exhibits excellent selectivity for Hg2+. The limit of detection (LOD) of Hg2+ is 30 nM by the naked eye and 3 nM by UV–vis spectroscopy, which is lower than the mercury toxic level defined by the U.S. Environmental Protection Agency (10 nM). A good linear relationship (R2 = 0.993) between the wavelength shift and Hg2+ concentrations indicates that our probe can be used for the quantitative assay of Hg2+. The results of Hg2+ detection in real environmental samples indicate the feasibility and sensitivity of our probe for application in complicated environmental samples.