Highly sensitive and selective fluorescent sensor for visual detection of Cu2+ in water and food samples based on oligothiophene derivative

A novel oligothiophene-derived colorimetric and fluorescent sensor 3TDB was designed and synthesized. The sensor 3TDB showed visible color change from colorless to yellow and the fluorescence was immediately decreased in aqueous media upon the addition of Cu2+. This sensor showed highly selective, sensitive, and turn-off fluorescence response to Cu2+ over other metal ions with a low detection limit of 4.2 x 10(-7) M. The sensor 3TDB for visual detection of Cu2+ showed high anti-interference ability in the co-existence of other metal ions and fast response time within 20 s in a wide pH range. The Cu2+-binding mode and recognition mechanism of the sensor were investigated by using Job's plot, FTIR, HRMS, and the DFT calculations. Moreover, the sensing behavior was found to be reversible with addition of EDTA, which indicated that 3TDB could act as a nice candidate for Cu2+ and EDTA controlled "ON-OFF-ON" fluorescence switch. Furthermore, the sensor 3TDB was successfully applied to detect Cu2+ in real water and food samples with satisfactory results.