Formamidinium iodide for instantaneous and fluorescent detection of Pb2+ in water

The visual and instantaneous detection of trace levels of toxic lead ions (Pb2+) in water is still challenging. In this study, a perovskite precursor-based fluorescent sensor for visual and instantaneous detection of toxic Pb2+ in aqueous media has been demonstrated. A solution of Formamidinium Iodide (CH5IN2) salt showed excellent fluorescence quenching ability upon the addition of Pb2+ due to the formation of perovskite. Interestingly, this sensor requires three seconds for visual and instantaneous detection of Pb2+ 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 Pb2+ in the range of 100 nM to 1 mM. The sensor also showed a low detection limit of 100 nM for Pb2+, which is lower than the safety limit of Pb2+ in drinking water. In addition, the sensor showed excellent selectivity against a variety of interfering heavy metal ions including Hg2+, Cr3+, Zn2+, Cd2+, 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 Pb2+. Furthermore, the sensor demonstrated excellent feasibility for the detection of Pb2+ in real water samples, which confirms its potential for testing Pb2+ in environmental samples.