Formamidinium iodide for instantaneous and fluorescent detection of Pb in water

The visual and instantaneous detection of trace levels of toxic lead ions (Pb 2+ ) in water is still challenging. In this study, a perovskite precursor-based fluorescent sensor for visual and instantaneous detection of toxic Pb 2+ in aqueous media has been demonstrated. A solution of Formamidinium Iodide (CH 5 IN 2 ) salt showed excellent fluorescence quenching ability upon the addition of Pb 2+ due to the formation of perovskite. Interestingly, this sensor requires three seconds for visual and instantaneous detection of Pb 2+ in the range of 1 μM to 1 mM, which is the fastest response compared to the literature reports to the best of our knowledge. Furthermore, this sensor showed a linear fluorescent response with various concentrations of Pb 2+ in the range of 100 nM to 1 mM. The sensor also showed a low detection limit of 100 nM for Pb 2+ , which is lower than the safety limit of Pb 2+ in drinking water. In addition, the sensor showed excellent selectivity against a variety of interfering heavy metal ions including Hg 2+ , Cr 3+ , Zn 2+ , Cd 2+ , Ag + , etc. The excellent performance of the sensor could be attributed to the high electrostatic potential energy of the formamidinium cation (FA + ), which was calculated using Density Functional Theory (DFT), that makes FA + highly interactive toward Pb 2+ . Furthermore, the sensor demonstrated excellent feasibility for the detection of Pb 2+ in real water samples, which confirms its potential for testing Pb 2+ in environmental samples. Pb 2+ detected in water within three seconds. Formamidinium Iodide shows excellent fluorescence quenching with addition of Pb 2+ due to FAPbI 3 perovskite formation. Wide linear detection range of Pb 2+ , 100 nM to 1 mM. Detection limit of 100 nM for Pb 2+ and excellent selectivity.