A single probe to sense Al(III) colorimetrically and Cd(II) by turn-on fluorescence in physiological conditions and live cells, corroborated by X-ray crystallographic and theoretical studies.

A pyridine-2-carbohydrazide functionalized conjugated fluorophoric Schiff base ligand (L₁) specifically senses Al(3+) and Cd(2+) ions through significant changes in its absorption and emission spectral behavior, respectively, in physiological conditions. The spectral changes are in the visible region of the spectrum and thus facilitate naked eye detection. Apart from the visible changes, an in-field device application was demonstrated by sensing these ions in paper strips coated with L₁. The crystal structure of the L₁-Cd complex provided additional insight of the metal coordination attributes of L₁. Interestingly, fluorescence microscopic studies demonstrated that the ligand L₁ could also be used as an effective probe in imaging experiments for the detection of intracellular Cd(2+) ions in HeLa cells, without any toxicity to these model human cells.