Highly sensitive fluorometric detection of Zn2+ ion by calix[4]arene derivative appended 4-biphenylcarbonitrile

A novel calix[4]arene derivative bearing 4-biphenylcarbonitrile unit (CCP) was developed for the selective fluorescent sensing of Zn2+ with a discriminating enhancement of 14-folds over the other metal ions. CCP exhibited highly selective and sensitive fluorescence “off-on” recognition to Zn2+ with a 1:1 binding stoichiometry in aqueous solution (EtOH/H2O, 8/2, v/v). The binding constant was calculated as 3.50 × 105 M−1 with detection limit of 0.31 μM, which presented a pronounced sensitivity toward Zn2+ ion. To check its applicability, an easy prepared test paper strip of CCP was made for rapid and selective detection of Zn2+. Also, the determination of Zn2+ in water samples was evaluated. Otherwise, the results demonstrated that the binding between CPP and Zn2+ is chemically reversible in presence of only cysteine among the various amino acids and anions, resulting in “on–off” type sensing of cysteine.