Selective fluorescent detection of Zn2+ by a rhodanine-based chemosensor

A rhodanine-based fluorescent chemosensor DHM, 3-[(E)-{[4-(diethylamino)-2- hydroxyphenyl]methylidene}amino]-2-sulfanylidene-1,3-thiazolidin-4-one, has been designed and synthesized. Sensor DHM showed unique optical properties with large fluorescence change on detecting Zn2+. Most cations did not disturb the binding of DHM with Zn2+, while Co2+ and Cu2+ displayed fluorescence quenching and Fe2+, Fe3+, and Ni2+ did some interference. With outcomes of Job plot and electrospray ionization (ESI)-mass data, the binding ratio of DHM to Zn2+ was determined as a 1:1. Moreover, DHM could detect Zn2+ with a low detection limit (1.33 mu M). DHM could efficiently analyze Zn2+ in a real environment with positive recovery and relative standard deviation (RSD) and be recyclable reliably with ethylenediaminetetraacetic acid (EDTA). DHM-doped test kits can be readily used for recognizing Zn2+. The binding feature of DHM to Zn2+ was illustrated by ESI-mass, nuclear magnetic resonance (NMR) titration, and calculations.