A new Schiff-based chemosensor for chromogenic sensing of Cu²⁺, Co²⁺ and S^2- in aqueous solution: Experimental and theoretical studies

A new Schiff-based multifunctional colorimetric chemosensor 1 was developed for the detection of various analytes (Cu²⁺, Co²⁺ and S^2-). Sensor 1 could simply monitor Cu²⁺ and Co²⁺via the naked eye in an aqueous environment. The quite low detection limits were found to be 0.19 μM for Cu²⁺ and 0.18 μM for Co²⁺, which were much lower than the values recommended by the World Health Organization (WHO) for Cu²⁺ (31.5 μM) and Environmental Protection Agency (EPA) for Co²⁺ (17 μM). Importantly, 1 showed high preferential selectivity for Cu²⁺ and Co²⁺ over competitive metal ions. For practical applications, the sensing abilities of 1 for detecting Cu²⁺ and Co²⁺ were examined in real water samples. In addition, 1 exhibited high selectivity for S^2- even in the presence of other anions without any interference. Moreover, the sensing mechanisms of 1 toward Cu²⁺, Co²⁺ and S^2- were explained by theoretical calculations.