Tuning the fluorescence emission of water-stable CsPb(Br/I)3 perovskite nanocrystal probes for naked-eye visual detection of mercury ion

All-inorganic cesium lead halide perovskite nanocrystals (PNCs) have rarely been reported in analytical chemistry, especially in water environment analysis, due to their high susceptibility to environmental conditions. Herein, we investigate and report a method of visual detection of Hg2+ concentration in aqueous solution using CsPb(Br/I)3 PNCs. In this strategy, three kinds of CsPb(Br/I)3 PNCs with FL emission peaks of 551 nm, 591 nm, and 617 nm were used to detect Hg2+, and it was found that Hg2+ can quench the fluorescence of CsPb(Br/I)3 PNCs and blue-shift the maximum FL emission peak. We also found that the Hg2+ concentration has a good linear relationship with the fluorescence quenching rate (I0/I) and FL emission peak shift (Δλ) of CsPb(Br/I)3 PNCs. With the red-shift of the probe FL emission peak, the detected concentration range of Hg2+ gradually expanded. Therefore, the possibility of detecting Hg2+ concentration without huge equipment was detailed by examining the red (R), green (G), and blue (B) values of photographs of CsPb(Br/I)3 PNCs with Hg2+. Under a 365 nm ultraviolet (UV) lamp, the solution color of CsPb(Br/I)3 PNCs emission peaks at 591 nm gradually changes from orange to green with the increase of Hg2+ concentration, which has an excellent visualization effect. The method presented here has the potential to establish a new analytical method for the visual detection of Hg2+ in aqueous environments, and may also facilitate the application of all-inorganic cesium lead halide perovskite nanocrystals for analytical detection in aqueous environments.