A new Schiff-base chemosensor for selective detection of Cu2+ and Co2+ and its copper complex for colorimetric sensing of S2− in aqueous solution

Abstract

A new Schiff-base colorimetric chemosensor 1 was developed for the detection of Cu²⁺, Co²⁺ and S²⁻. Sensor 1 could simply monitor Cu²⁺ and Co²⁺ by a color change from colorless to yellow. The binding modes of 1 to Cu²⁺ and Co²⁺ were determined to be a 2 : 1 complexation stoichiometry through Job's plot and ESI-mass spectrometry analysis. The detection limits (0.02 μM and 0.63 μM) for Cu²⁺ and Co²⁺ were lower than the recommended values (31.5 μM and 1.7 μM) by the World Health Organization (WHO) for Cu²⁺ and the Environmental Protection Agency (EPA) for Co²⁺, respectively. Importantly, 1 could detect and quantify Cu²⁺ in real water samples. In addition, the Cu²⁺-2·1 complex could be used as a highly selective colorimetric sensor for S²⁻ in the presence of other anions without any interference. Moreover, the sensing mechanisms of Cu²⁺ and Co²⁺ by 1 were explained by theoretical calculations.