New fluorescence probe for Fe3+ with bis-rhodamine and its application as a molecular logic gate

A bis-rhodamine based fluorescent probe R1 for naked-eye detection of Fe3+ with enhanced sensitivity compared to a mono-rhodamine derivative that shows selectivity for Hg2+, has been synthesized. The 1:1 stoichiometric structure of R1 and Fe3+ is confirmed using a Job's plot estimation and density functional theory calculations. The reversibility of R1 is verified through its spectral response toward Fe3+ and S2- titration experiments. Using Fe3+ and S2- as chemical inputs and the fluorescence intensity signal as outputs, R1 can be utilized as an INHIBIT logic gate at molecular level. Fluorescent imaging for Fe3+ in living HL-7702 cells have also been successfully performed. (C) 2015 Elsevier B.V. All rights reserved.