Fluorescent detection of Zn(II) and In(III) and colorimetric detection of Cu(II) and Co(II) by a versatile chemosensor

A new versatile chemosensor 1 ((Z)-N'-(quinolin-2-ylmethylene)furan-2-carbohydrazide), based on quinoline and furan, has been synthesized. Sensor 1 showed immediate responses toward Zn2+ and In3+ ions through selective fluorescence enhancement in different solvent conditions, respectively. In addition, sensor 1 could detect Cu2+ and Co2+ by "naked eye" color changes from colorless to pale yellow in a near-perfect aqueous solution. This observation was the first case that a single sensor can detect the four metal ions. The binding modes of 1 to Zn2+, In3+, Cu2+ and Co2+ were verified through Job plots and ESI-mass spectrometry analyses. The limits of detection (0.33 mu M, 0.23 mu M and 0.06 mu M) for Zn2+, Cu2+ and Co2+ were far lower than the World Health Organization (WHO) guidelines (76 mu M for Zn2+ and 31.5 mu M for Cu2+) and Department of Environmental Protection (DEP) guideline (1.7 mu M for Co2+) for drinking water. Moreover, sensor 1 could quantify Zn2+ and Co2+ in water samples. The sensing mechanisms of Zn2+, In3+ and Cu2+ by sensor 1 were explained by theoretical calculations. (C) 2018 The Korean Society of Industrial and Engineering Chemistry. Published by Elsevier B.V. All rights reserved.