Facile Synthesis, Size-Separation, Characterization, and Antimicrobial Properties of Thiolated Copper Clusters

Abstract

Metal nanomaterials have attracted extensive attention in biological labeling and imaging due to their controllable physical and chemical properties. Recently, a lot of effort has been devoted to preparing various ultrasmall and functional copper nanoclusters (CuNCs) with different emissions from blue to red, soluble both in organic and aqueous phases. Herein, a novel one-step synthetic method is proposed for the preparation of stable water-soluble glutathione-capped (GSH-capped) CuNCs. The resulting nanoclusters have a good dispersibility and stability in aqueous media. The stability was examined by several test experiments. The mass detection in ESI-HRMS mode allowed ionization of several doubly charged species with formula Cu5L6, Cu6L6, Cu7L6, Cu8L6, and Cu9L6 (L = C10H16N3O6S). The use of advanced separation techniques including liquid chromatography (HPLC), gel electrophoresis (PAGE), and capillary electrophoresis (CE) allowed the separation of several clusters, some of which are larger than Au-25(GS)(18), as shown by PAGE. To the best of our knowledge, this is the first report on successful size-separation of CuNCs. Moreover, the synthesized CuNCs show a dose-dependent antimicrobial effect. At lower cluster concentration the growth of bacteria is partially reduced. However, at higher concentrations, the bacterial growth is completely restricted.