Sub-nanometer sized Cu6(GSH)3 clusters: one-step synthesis and electrochemical detection of glucose

We report here a one-pot synthesis of sub-nanometer sized copper clusters capped with a water-soluble ligand, L-glutathione (SGH), through a chemical reduction process. The composition of the as-prepared Cu-6(SG)(3) nanoclusters was confirmed by electrospray ionization mass spectrometry (ESI-MS) and matrix-assisted laser desorption ionization time-of-flight mass spectroscopy (MALDI-TOF MS). The FTIR, H-1 NMR and XPS characterization methods showed that with the production of Cu-6(SG)(3) clusters and the formation of Cu-S bonds, the surface chemical environment of the clusters exhibited a significant change. The produced water-soluble clusters show aggregation-induced fluorescence upon the addition of ethanol into the cluster aqueous solution. By loading on the TiO2 support, the as-prepared copper nanoclusters were successfully applied to the electrochemical detection of glucose. Compared to large Cu nanoparticles, the Cu-6(SG)(3) nanoclusters exhibited higher sensitivity and a wider linear range for glucose detection.