A quinoline-based fluorescent probe for selective detection and real-time monitoring of copper ions - a differential colorimetric approach.

A quinoline moiety was used as a building block for designing a probe for the selective detection of copper ions in a partially aqueous medium. We have developed a molecular sensing system which gives insight into the complex physiological and redox aspects of labile copper. The probe provides a colorimetric approach for distinguishing cuprous and cupric ions along with their simultaneous discrimination from other metal ions in the visible range of the spectrum. The chemosensor showed a remarkable fluorescence enhancement along with a significant bathochromic shift of about 35 nm. The detection limit of the probe was found to be 1.03 μM which is optimally favorable to be applied in real-time monitoring. Fabrication of paper strips with the probe was done to detect the presence of cuprous ions in the real sample. The value of the binding constant (1.37 × 104 M-1) suggests stable complex formation between the metal ion and the sensing probe. The photoluminescence and structural aspects of the chemosensor were characterized by using fluorescence, absorption, ESI-MS, and 1H NMR spectroscopy. Furthermore, the cytotoxic nature and bioimaging properties of the probe were interpreted in vitro on RAW 264.7 macrophage cell lines and peripheral blood mononuclear cells (PBMCs) respectively.