Promoted colorimetric response of spirooxazine derivative: a simple assay for sensitive mercury(II) detection

A spirooxazine derivative 1,3-dihydro-1,3,3-trimethyl-spiro[2-H-indole-2-2′-[2H-1,4] oxazino [2,3-f] [1, 10] phenanthroline] (compound 1) was explored as a sensitive Hg²⁺ probe. Sensing behavior toward various metal ions including Hg²⁺, Na⁺, K⁺, Ag⁺, Pb²⁺, Ni²⁺, Fe²⁺, Cu²⁺, Zn²⁺, Cd²⁺, Co²⁺, Ba²⁺, Mn²⁺, Cr³⁺, Al³⁺ and Fe³⁺ was investigated by UV–Vis in acetonitrile solution. Benefiting from the strategy of visual detection, this compound showed preferable selectivity and sensitivity for Hg²⁺ with a detection limit of 0.68 ppm. In addition, the color of the solution was different, when dropping different concentrations of mercury ions (10⁻⁸–10⁻² M) into the probe (compound 1). This remarkable color variation (lavender to green) could be observed easily by a naked eye. The approach can not only detect the Hg²⁺ in acetonitrile solution, but also can detect the Hg²⁺ in sewage and industrial effluents.