Solvatochromic AIE luminogens as supersensitive water detectors in organic solvents and highly efficient cyanide chemosensors in water

A novel class of tetraphenylethene (TPE) derivatives TPEM and TPEBM containing dicyanovinyl groups were synthesized, possessing remarkable dual properties of solvatochromism and aggregation-induced emission (AIE). The combination of the electron-donating TPE and the electron-accepting dicyanovinyl group endow both compounds with a prominent solvatochromic effect, with emissions strongly dependent on solvent polarity and tunable from blue to red by changing the solvent from apolar to polar. They are found to be useful as fluorescent indicators for the qualitative and quantitative detection of low-level water content in organic solvents, and the detection limit can be as low as 63 ppm and 109 ppm in THF, respectively. Meanwhile, TPEM and TPEBM demonstrate typical AIE features and emit green-yellow and orange light in their aggregated states, respectively. Based on the AIE feature of TPE and the nucleophilic addition of cyanide, both compounds can act as colorimetric and fluorescent sensors for highly sensitive and selective detection of CN− in aqueous media under the assistance of cetyltrimethylammonium bromide (CTAB). The low detection limit of 0.2 μM as well as a short sensing process of only 100 seconds promise their practical application for detecting cyanide in drinking water. Furthermore, the development of easy-to-prepare test papers provides a convenient and reliable approach to monitor CN− in daily applications without resorting to instrumental analysis.