Synthesis of cysteine-functionalized water-soluble luminescent copper nanoclusters and their application to the determination of chromium(VI)

A facile, one-pot green method is presented for the preparation of water-soluble luminescent copper nanoclusters (Cu-NCs) from copper dichloride and cysteine as the precursor and stabilizer, respectively. The Cu-NCs are characterized by high resolution transmission electron microscopy, X-ray photoelectron spectroscopy, fluorescence, UV-Vis, and Raman spectroscopy. The Cu-NCs have an average size of 3.5 nm and are stable in aqueous solution at least for 2 weeks. Under photo excitation with 365 nm light, the Cu-NCs display strong green fluorescence with the maximum of emission at 490 nm and a quantum yield of 5.6 %. Fluorescence is quenched by Cr(VI) ion, and this effect was exploited to develop a highly selective method for the determination of Cr(VI). The detection limit of this probe is as low as 43 nM.