Dual-channel detection of Cu(2+) and F(-) with a simple Schiff-based colorimetric and fluorescent sensor.

A simple and easily synthesized colorimetric and fluorescent receptor 1, based on 4-diethylaminosalicylaldehyde moieties as a binding and signaling unit, has been synthesized and characterized. The receptor 1 has a selective colorimetric sensing ability for copper (II) ion by changing color from colorless to yellow in aqueous solution, and could be utilized to monitor Cu(II) over a wide pH range of 4-11. In addition, the detection limit (12μM) of 1 for Cu(2+) is much lower than that (30μM) recommended by WHO in drinking water, and its copper complex could be reversible simply through treatment with a proper reagent such as EDTA. Moreover, receptor 1 exhibited both a color change from colorless to yellow and fluorescence enhancement with a red shift upon addition to F(-) in DMSO. The recognition mechanism was attributed to the intermolecular proton transfer between the hydroxyl group of the receptor and the fluoride.