A Supersensitive Probe for Rapid Colorimetric Detection of Nickel Ion Based on a Sensing Mechanism of Anti-etching

Redundant nickel is harmful to human health and can result in skin diseases, allergies, or cancer. Although many probes based on noble metal nanoparticles have been established for rapid heavy metal ion detection by the naked eye or ultraviolet–visible (UV–vis) spectroscopy, few noble metal nanomaterials have been developed for Ni²⁺ detection. In this study, we propose novel triangular silver nanoprisms (AgNPRs) stabilized with glutathione (GSH) for rapid colorimetric detection of Ni²⁺ based on a sensing mechanism of anti-etching, which has been affirmed by Raman spectra, UV–vis spectra, transmission electron microscopy, and dynamic light scattering. At the optimal experimental parameters, our GSH-AgNPR-based Ni²⁺ probe has an excellent selectivity compared with those of 26 other ions because Ni²⁺ can inhibit the AgNPR etching by iodide ion (I^–) (i.e., anti-etching) while other ions cannot. The limit of detection (LOD) of our Ni²⁺ probe is 50 nM via the naked eye and 5 nM via UV–vis spectroscopy. They are both negligible compared with the permissible limit of Ni²⁺ in drinking water (0.34 μM) prescribed by the World Health Organization. In particular, the latter is far lower than the LOD values of other reported Ni²⁺ probes based on noble metal nanomaterials. A satisfying linear relationship reinforces that our probe can be utilized for the quantitative analysis of Ni²⁺. The detection of real water samples indicates that our probe could be used for rapid Ni²⁺ colorimetric detection with supersensitivity and excellent selectivity in real environmental water samples

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 (<i>R</i>² = 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