Water-soluble Au25(Capt)18 nanoclusters: synthesis, thermal stability, and optical properties

This work was motivated by the unsatisfactory stability of Au-25(SG)(18) in solution under thermal conditions (e.g. 70-90 degrees C for DNA melting). Thus, we searched for a better, water-soluble thiol ligand. Herein, we report a one-pot synthesis and investigation of the stability and optical properties of captopril (abbreviated Capt)-protected Au-25(Capt)(18) nanoclusters. The Au-25(Capt)(18) (anionic, counterion: Na+) nanoclusters were formed via size focusing under ambient conditions. Significantly, Au-25(Capt)(18) nanoclusters exhibit largely improved thermal stability compared to the glutathione (HSG) capped Au-25(SG)(18). Both Au-25(Capt)(18) and Au-25(SG)(18) nanoclusters show fluorescence centered at similar to 700 nm. The chiral ligands (Capt, SG, as well as chirally modified phenylethanethiol (PET*)) give rise to distinct chiroptical features. The high thermal stability and distinct optical properties of Au-25(Capt)(18) nanoclusters render this material quite promising for biological applications.