Ion-Pair Ligand-Assisted Surface Stoichiometry Control of Ag2S Nanocrystals

摘要

Surface atom stoichiometry is controlled for Ag2S NCs through ion-pair ligand-assisted surface reactions.Predominantly cation-rich-surfaced Ag2S NCs(Ag-Ag2S),anion-rich-surfaced Ag2S NCs(S-Ag2S),and perfectly stoichiometric Ag2S NCs(st-Ag2S)are prepared.Various combinations of cation and anion pairs are studied for Ag2S NC surface reactions.Depending on the hardness/softness of the ion-pair ligands,the NC surface shows disparate reactions of(i)X-type anion replacing native X-and L-type ligands,(ii)binding as the whole ion-pair ligand,and(iii)one-to-one exchange by the positive cation ligand.Ion-pair-assisted surface chemistry enables the synthesis of perfectly stoichiometric-surfaced Ag2S NCs,which shows that the fluorescence intensity increased by more than ten times,and epitaxial ZnS growth on st-Ag2S was enhanced more than three times when compared with non-stoichiometric NCs.