Aluminum-Enhanced Fluorescence of Cu 8 Nanoclusters: An Effective Method for Sensitive Detection of Fluoride in Aqueous and Bioimaging.

Here, we report glutathione-protected water-soluble copper nanoclusters (Cu 8 NCs) with excellent properties of high stability, large Stokes shift, and low toxicity. The molecular formula and structure of the Cu 8 NCs were confirmed through good agreement between spectroscopic results and theoretical calculations. The origin of optical properties and chemical stability of the Cu 8 NCs was determined through natural bond orbital analysis combined with time-dependent density functional theory calculations. It was found that the fluorescence emission and quantum yields of Cu 8 NCs could be effectively enhanced by aluminum(III) ions (Al 3+ ) through the aggregation-induced enhanced emission mechanism. On the basis of the strong reaction of Al 3+ with F - , the enhanced fluorescence of the obtained Cu 8 NC-Al 3+ ensemble could be selectively turned off by fluoride ions (F - ), achieving highly sensitive detection of F - in aqueous with a detection limit of 0.16 μM. Also, the fluorescence of Cu 8 NC-Al 3+ ensemble quenched by F - could be enhanced again upon binding additional Al 3+ . In addition, the proposed Cu 8 NC-Al 3+ ensemble with enhanced fluorescence was used for bioimaging in vitro and in vivo. These results indicated that Cu 8 NCs are promising materials for sequential sensing and bioimaging in the future.