Facile and rapid synthesis of copper nanoclusters as a fluorescent probe for the sensitive detection of fluoride ions with the assistance of aluminum

A facile, environmentally friendly, and rapid synthesis approach has been developed for the preparation of copper nanoclusters (CuNCs). It takes 2 min to synthesize CuNCs only by simply tuning pH value of glutathione (GSH) and copper ions mixture at room temperature. CuNCs exhibit an emission maximum peak at 646 nm with excitation maximum at 340 nm. A luminescent off-on-off nanoswitch is triggered by aluminum (Al3+) and fluoride (F) ions in terms of physical state changes between aggregation and dispersion of CuNCs. Al3+ ions can immediately stimulate to produce aggregation-induced emission (AIE) of CuNCs. The molecular vibrations and rotations of rigidified ligands on the surface of aggregation of CuNCs are confined, reducing the nonradiative decay pathway. So, fluorescence emission of aggregated CuNCs is greatly enhanced. This specific behavior of CuNCs by fluorescent light-up mode is capable to quantify Al3+ in the range from 0.1 to 200 mu M with LOD of 59 nM. Moreover, we explore the use of disaggregation-caused quenching (DCQ) of CuNCs for the detection of F ions by taking advantages of the higher affinity of Al3+ and F over that of Al3+ and carboxyl on surface groups of CuCNs. So, AIE of CuNCs is greatly inhibited. This system exhibits signal-off response towards F with a detection range from 5 to 80 mu M with LOD of 1.64 mu M. Importantly, this approach has been successfully applied to the detection of Al3+ in tap and lake water as well as F ions in three brands of toothpaste. It has great potential to expand the application of CuNCs-based sensors in the field of daily necessities and environmental monitoring.