CsPbBr3 Perovskite–Coated Paper Substrate for the Cost‐Effective Detection of Fluoride, Chloride, and Iodide Ions in Water

Developing a simple and cost‐effective substrate for the detection of the halide ions present in water is extremely important due to their adverse effects at higher concentrations. A good substrate should behave differently in the presence of different halide ions. Herein, a CsPbBr3‐coated paper substrate is used for the detection of fluoride, chloride, and iodide ions. As a result of the fast anion exchange reactions, in the presence of each halide ion, the CsPbBr3‐coated paper shows different emission behaviors. The presence of chloride and iodide ions results in blueshifted and redshifted absorption and emission, respectively. In the presence of fluoride ions, anion exchange followed by decomposition of the perovskite nanocrystal is observed. The anion exchange reactions of CsPbBr3 perovskites are faster than the moisture‐induced decomposition, which enables the detection of micromolar concentrations of fluoride, chloride, and iodide ions in water. Maintaining the concentrations of various halide ions in drinking water is extremely important due to their adverse health effects at higher concentrations. Herein, the color changes in emission due to the fast anion exchange reactions in a lead halide perovskite coated paper substrate are used to detect the halide ions in water in a cost effective manner.