Ligand-Induced Red-Emitting Copper Nanoclusters for Selective Fluorescence Determination of Aluminum Ions

Monitoring levels of excessive aluminum ions (Al³⁺) is crucial as it can harm the immune system, reduce enzyme activity, cause cell death, and damage environmental and biological systems. Developing a fast and efficient Al³⁺ ion determination method is the key to addressing this issue. In this work, red-emitting fluorescent copper nanoclusters (CuNCs) were synthesized using N-acetyl-l-cysteine (NAC) as a ligand and CuCl₂·2H₂O through a facile procedure. The NAC-CuNCs exhibited a large Stokes shift and displayed remarkable luminescence properties. A method for detecting Al³⁺ through a fluorescence probe was proposed. Its fluorescence mechanism was also explored. The probe showed rapid responsiveness (within 1 min) to Al³⁺ ion determination. The detection limit for Al³⁺ was found to be 19.7 nM, which is significantly lower than the WHO's value and most reports, with a linear range of 0-52.9 μM. The determination of Al³⁺ concentrations in actual water using the fluorescence probe yielded satisfactory outcomes. Moreover, the visual detection of Al³⁺ ions was also achieved through a smartphone, which can enhance its fast and practical detection.