Selective and Sensitive Fluorescein-Benzothiazole Based Fluorescent Sensor for Zn2+ Ion in Aqueous Media

An efficient fluorescent sensor based on fluorescein-benzothiazole (FB) for Zn2+ ion was synthesized and characterized systematically. FB exhibited selective and sensitive recognition toward Zn2+ in MeCN-H2O (v/v = 2/1) over other cations due to the spirolactam ring-opening power of Zn2+. The complexation property of FB with Zn2+ ion was examined by 1H NMR, 13C NMR and FTIR experiments. The stoichiometric ratio of the FB-Zn2+ complex was determined from a Job plot to be 1:1. The binding constant (Ka) of Zn2+ binding to FB was found to be 4.22 × 104 M− 1, with a detection limit of 5.64 μM. In addition, the practical utility of FB was explored in the form of test strips. [Figure not available: see fulltext.].