Synthesis of Highly Stable Surfactant-free Cu₅ Clusters in Water

Abstract

We report the synthesis, for the first time, of small, highly monodisperse Cu 5 clusters in water without any surfactant or protective agent. For this purpose, we used a new approach based on the kinetic control of the reaction, which is achieved with an electrochemical method and using a solution with almost no conductivity (i.e., without added electrolytes commonly used in electrochemical methods). This allows the application of extremely small current densities needed to focus the reaction to synthesize only one selected cluster size. Clusters were characterized by ultraviolet−visible (UV−vis) and fluorescence spectroscopies, atomic force microscopy, electrospray ionization time-of-flight mass spectrometry, X-ray photoelectron spectroscopy, extended X-ray absorption fine structure, and Xray absorption near-edge spectroscopy, showing the presence of only Cu clusters with five atoms. Contrary to what should be expected, such clusters are very stable and remain unaltered in solution, for at least one year, because of their huge band gap (4.07 eV). Moreover, such Cu 5 clusters are extremely stable to UV irradiation, temperature, and pH.

Exploring the properties of Ag5–TiO2 interfaces: stable surface polaron formation, UV-Vis optical response, and CO2 photoactivation

“…Instead, the presence of a molecule-like HOMO-LUMO gap drastically transforms their chemical and physical properties, thus creating innovative materials for applications including luminescence, 2 sensing, 3 therapeutics, 4 energy conversion, 5 catalysis, 6 and electrochemistry. 7,8 Nowadays, these so-called atomic quantum clusters (AQCs) can be synthesized by kinetic control using electrochemical methods, [9][10][11] showing an exceptional chemical and thermo-dynamical stability in solution over the whole pH range. 9 As discussed in ref.…”

“…7,8 Nowadays, these so-called atomic quantum clusters (AQCs) can be synthesized by kinetic control using electrochemical methods, [9][10][11] showing an exceptional chemical and thermo-dynamical stability in solution over the whole pH range. 9 As discussed in ref. 9, high monodispersity of synthesized AQCs (e.g., Cu 5 ) has been achieved since the method of cluster synthesis is extremely size-selective.…”

Helium nanodroplets doped with copper and water

“…Some catalytic reactions may be promoted by atoms or small clusters of copper [11,12]. Huseyinova et al have reported the synthesis of surfactant-free, nearly mono-disperse Cu 5 clusters in water that are stable to UV irradiation, elevated temperature, and a wide range of pH [13]. Their catalytic activity has not yet been measured, but several theoretical studies of water dissociation on Cu 7 have been reported [14][15][16].…”

Different Color Emissive Copper Nanoclusters for Cancer Cell Imaging

“…[1i] In this context, synthesis and stabilization of CuNCs in an environmentally safe solvent like water is important not only to find ag reen synthesis route, but also for their applications in biosensing and bioimaging. [5] Biomolecules have been attractive stabilizinga gentsf or the synthesis of water soluble CuNCs,W ang and co-workersh ave recently synthesized DNA-hosted CuNCsi na queous medium for identification of their polymorphism. [6] Chattopadhyaya nd co-workersh ave synthesized blue fluorescentC uNCsi na queous mediumfor fluorescent imaging of HeLa cells.…”

“…[5h] Therefore, our resultsa re comparable with the other previously reported studies in which smallm olecules have been used as stabilizing agents. From MALDI-TOF analysis, it has been found that the blue CuNC has am olecular formula of Cu 3 (GS), the cyan one is com-posed of two species:C u 5 (GS) 5 and Cu 9 (GS) 5 ,w hereast he green and orange red nanoclustersa re composed of Cu 10 (GS) 9 and Cu 13 (GS) 13 ,r espectively.T he number of Cu atoms for all these CuNCs never exceeds 13. This observation is consistent with the previously reported work by Rivas and co-workers, which describes that only coppern anoclusters in which the number of coppera toms within the nanocluster is 13 show fluorescence.…”