Medium-dependent selectivity for Cu2+ and glutathione by a near-infrared fluorescent probe

A novel near-infrared Schiff base fluorescent probe was synthesized. The probe displayed medium-dependent selectivity and could specifically recognize Cu2+ in EtOH/H2O (9:1, v/v) while respond to glutathione (GSH) in THF/H2O (9:1, v/v). Addition of Cu2+ to the probe solution caused obvious fluorescence quenching and color change. The detection limit was calculated to be 37 nM. The probe could specifically detect GSH through fluorescence turn-on in THF/H2O (9:1, v/v) medium based on GSH-induced hydrolysis of the probe, with the detection limit as low as 20 nM. The sensing mechanism of the probe was verified by spectral analysis and density functional theory (DFT) calculations. Application of the probe to real water samples analysis and bioimaging was achieved.