Core engineering of paired core-shell silver nanoclusters

Unlike the facile modulation of surface structure through protecting ligands, the core shielded by outer shell of silver nanoclusters is still hard to be controlled. Ligand effects may seep into the incipient growth of silver core. However, the comparable cases to validate such hypothesis are currently lacking. Herein, we shed light on two core-shell silver nanoclusters, Ag7S6@Ag48 (SD/Ag55b, SD = SunDi) and Ag6S6@Ag48 (SD/Ag54b), differing in only one silver atom in the core which varies from a pentagon-bipyramidal Ag7 to an octahedral Ag6 while keeping the Ag48 shielding shell almost the same. Although no direct bonding between alkynes and silver core is observed in them, we propose that the ligand effect still exerts profound influences on the size and geometry of silver core. The solution behaviours and complete ligand-exchange reaction of SD/Ag55b in CH2Cl2 are investigated using electrospray ionization mass spectrometry. Due to more and stronger argentophilic interactions, SD/Ag55b exhibits room-temperature phosphorescence with a 40 nm red-shift compared to that of SD/Ag54b in CH2Cl2. This work not only presents effective fabrication of silver nanoclusters via synergism of dithiophosphate and alkyne ligands, but also provides us a pair of comparable examples to understand substitution group effect of protecting ligand on the core structures and properties.