A fluorescent "ON-OFF-ON" switch for the selective and sequential detection of Hg 2+ and I - with applications in imaging using human AGS gastric cancer cells.

A new fluorescent "on-off-on" probe (BIPQ) is designed and developed which selectively binds with Hg ²⁺ ; its emission intensity is quenched almost 40-fold at 455 nm without interference from other metal cations. On gradual addition of I ^- to the solution of BIPQ-Hg ²⁺ , the emission reverts to its original intensity. The limits of detection of BIPQ for Hg ²⁺ and I ^- are found to be on the order of 3.12 × 10 ^-9 and 5.48 × 10 ^-8 M, respectively, which shows clearly that BIPQ can sense Hg ²⁺ at a very minute level. DFT and TDDFT studies are conducted with the probe to establish similarity between theoretical and experimental outcomes. Finally, to demonstrate its practical benefit in biological fields, live cell imaging experiments with BIPQ are carried out to detect Hg ²⁺ in human AGS gastric cancer cell lines.