Simple chalcone-based chemosensor for colorimetric naked-eye detection of Al3+ and Cu2+ ions

A highly selective and sensitive Al3+ and Cu2+ ion receptor (4-(dimethylamino)-2′-hydroxychalcone) was designed, synthesized, and characterized via standard techniques such as FT-IR and 1H NMR spectroscopy and GC-MS. The solvatochromism and keto–enol tautomerism of the material were studied in various solvents. The selectivity of the receptor was investigated using UV–visible and fluorescence spectrophotometry. The receptor was found to behave as a highly selective colorimetric turn-on sensor for the Al3+ ion by changing color from yellow to red with an association constant of 1.62 × 104 M−1 and a low detection limit of 1.02 × 10−7, and as a turn-off sensor for Cu2+ with an association constant of 4.98 × 104 M−1 and detection limit of 9.62 × 10−7. The present investigation confirms that the receptor acts as a selective fluorescence probe for the detection of Cu2+ ions. The highlight of this work is that the receptor is effective as a naked-eye sensor for Al3+ and Cu2+ ions.