A fast, highly selective and sensitive colorimetric and fluorescent sensor for Cu2+ and its application in real water and food samples

Abstract A new oligothiophene functionalized Schiff base sensor 3TDC has been successfully designed and synthesized. Sensor 3TDC exhibited “naked-eye” colorimetric and selective “on-off” fluorescence response toward Cu 2+ with high selectivity and sensitivity within a wide pH range. The binding ratio of the sensor 3TDC and Cu 2+ was determined to be 1:1 through fluorescence titration, Job's plot, 1 H NMR titration, FTIR and DFT studies. The detection limit is calculated to be as low as 2.81 × 10 −8  M, which is much lower than the allowable level of Cu 2+ in drinking water set by U.S. Environmental Protection Agency (~20 μM) and the World Health Organization (~30 μM). The binding constant (K a ) of Cu 2+ to sensor 3TDC was found to be 2.52 × 10 4  M −1 . Sensor 3TDC for Cu 2+ detection exhibited fast fluorescence response within 30 s and high anti-interference performance. Moreover, sensor 3TDC could be used as an effective fluorescent sensor for detecting Cu 2+ ions in various real water and food samples with good accuracy and high precision.