A colorimetric sensor for the sequential detection of Cu2+ and CN- in fully aqueous media: practical performance of Cu2+

A new highly selective colorimetric chemosensor 1 (E)-9-(((5-mercapto-1,3,4-thiadiazol-2-yl)-imino)methyl)-2,3,6,7-tetrahydro-1H, 5H-pyrido[3,2,1-ij]quinolin-8-ol was designed and synthesized for the sequential detection of Cu2+ and CN-. This sensor 1 exhibited an obvious color change from yellow to orange in the presence of Cu2+ in a fully aqueous solution. The detection limit (0.9 mu M) of 1 for Cu2+ is far lower than the WHO limit (31.5 mu M) for drinking water. In addition, the resulting Cu2+-2.1 complex can be further used to detect toxic cyanide through a color change from orange to yellow, indicating the recovery of 1 from Cu2+-2.1. Importantly, chemosensor 1 could be used to detect and quantify Cu2+ in water samples, and a colorimetric test strip of 1 for the detection of Cu2+ could be useful for all practical purposes.