Rhodamine-Based Chromo-/Fluorogenic Dual Signalling Probe for Selective Recognition of HgII with Potential Applications for INHIBIT Logic Devices and Cell-Imaging Studies

A new rhodamine-based dual signaling probe (L-3) has been found to display quick responses through visible colorimetric changes as well as fluorogenic properties on selective 1:1. binding to Hg2+, as delineated by absorption and :fluorescence titrations as well as by Job's method and ESI-MS+ studies. The fluorescent probe L-3 displays a 252-fold fluorescence enhancement on binding to Hg2+. A Benesi-Hilderband fit of the absorption titration data gives K-d = (32.01 +/- 0.74) mu m and a 1:1 binding stoichiometry. Owing its solubility in mixed organic/aqueous solvents as well as its cell permeability, L-3 could be used for in vitro/in vivo cell imaging of Hg2+ with no or negligible cytotoxicity. The detection limit of Hg2+ was calculated by the 3 sigma method to be 9.28 ng L-1. Moreover, the fluorescence of the L-3-Hg2+ system was turned off and its red colour disappeared when KI was added. Thus, the OFF-ON-OFF fluorescence sensing behaviour of L-3 observed in the presence of Hg2+ and I may.find applications in devices with logic gate functions.