A novel NIR ratiometric fluorescent probe has been developed for monitoring the dynamic changes of subcellular Cu ²⁺ and quantifying its concentration at the nanomolar level in living cells.

Two newly synthesized Schiff bases DMCA and DMBA were used for selective detection of Cd2+ over a wide range of other metal ions in acetonitrile (ACN)/ Tris-HCl buffer (10 mM, pH 7.32, v/v 2:1). The sensors can detect Cd2+ ions by colour changes from colourless to orange for DMBA and yellow to reddish for DMCA. Response of the probes towards metal ions was investigated by using UV-vis spectroscopy. The complex stoichiometry between the sensors, DMBA and DMCA, and Cd2+ was found to be 2:1 and the binding constants were calculated to be 2.65 ×1012 M-2 and 4.95 ×1012 M-2, respectively. The absorbance-based detection limits of DMBA and DMCA were calculated as 0.438 μM and 0.102 μM, respectively. The sensors were also successfully applied to real samples.