A dual-function colorimetric probe based on Carbazole-Cyanine dyad for highly sensitive recognition of cyanide and hypochlorous acid in aqueous media.

A dual-function colorimetric probe (Cz-Cy7) with an electron-donating carbazole tethered at the central position of heptamethine cyanine was designed and synthesized, and the performance on CN- and HClO detection were systematically investigated. With the addition of CN-, Cz-Cy7 exhibited remarkable changes in both UV-vis and fluorescence spectra with a good linear relationship to CN- concentration, and a discernible color change under daylight was observed. The limit of detection for CN- was found to be 9.1 nM in DMF and 0.09 μM in DMF/H2O. Meanwhile, Cz-Cy7 exhibited a highly sensitive response to HClO in the presence of other ROS (reactive oxygen species) based on the sensing mechanism of oxidative cleavage of olefinic C =  = C bond. The limit of detection for HClO was evaluated to be 14 nM in PBS buffer solution (containing 50% CH3CN). More importantly, the probe Cz-Cy7 showed good recovery and analytical precision in real water samples for both CN- and HClO detection, indicating it was feasible and reliable for practical application. Moreover, the test strips loaded with Cz-Cy7 were fabricated and validated to be a portable tool for the efficient detection of CN- and HClO by the naked eye.