An ESIPT blocked highly ICT based molecular probe to sense Zn (II) ion through turn on optical response: Experimental and theoretical studies

摘要

A simple and low cost optical sensor (L) is synthesized by the condensation reaction and characterized systematically. Among the various tested metal ions, L selectively interacts with Zn2+ ion by inducing a 17-fold high fluorescence intensity with a 60 nm blue shift of emission maxima, changing colorless solution to intense yellow solution in 20 % aqueous acetonitrile. A mechanism for selective turn on optical response of L for Zn2+ was studied using UV-vis absorption and Fluorescence emission and is correlated with theoretical results. We propose that, a dual mechanism (ESIPT/ICT) is responsible for selective sensing of Zn2+ in 20 % aqueous acetonitrile. The Job's plot, B-H plots and ESI-MS studies confirm the 1:1 stoichiometry between host-guest interaction. A reversible optical probe with nanomolar level detection limit is non-toxic and it could render pH dependent fluorescence measurements in a live physiological environment. The practical application of L for Zn2+ was explored through bio-imaging experiment in HeLa cells.