A simple, reversible, colorimetric and water-soluble fluorescent chemosensor for the naked-eye detection of Cu in ~100% aqueous media and application to real samples.

A simple, reversible, colorimetric and water-soluble fluorescent chemosensor ADA for the naked-eye detection of Cu was developed. Sensor ADA showed high selectivity and sensitivity toward Cu in 100% aqueous media over wide pH range. Sensor ADA exhibited a red-shift in the absorption spectra from 466 to 480nm that is accompanied by significant color change from light yellow to yellowish brown instantaneously. The Cu recognition is based on the chelation-enhanced fluorescence quenching (CHEQ) effect of the paramagnetic nature. The lowest detection limit is determined to be 15.8nM, which is much lower than the allowable level of Cu in drinking water set by U.S. Environmental Protection Agency (20μM) and the World Health Organization (~30μM). The 1:1 binding process was confirmed by fluorescence measurements, IR analysis and DFT studies. Moreover, sensor ADA was successfully applied for determination of trace level of Cu with 4 reuse cycles in various water samples, which affords promising potential in ion-detection field.