Metal ion-induced alloying and size transformation of water-soluble metal nanoclusters

The development of novel strategies for the synthesis of water-soluble alloy nanoclusters (NCs) and investigations of their alloying mechanisms are highly desirable. Herein, we report the design of a metal ion-induced alloying strategy for the synthesis of atomically precise water-soluble alloy NCs. The transformation of Au15(GSH)13 NCs as model seeds (here GSH denotes water-soluble glutathione) into Au18−xAgx(GSH)14 NCs was triggered using Ag(I) ions; subsequently, Au(III) ions were employed to convert the variable-composition Au18−xAgx(GSH)14 NCs into fixed-composition alloy Au26Ag(GSH)17Cl2 NCs. Monitoring of the alloying process showed that the formation of Au18−xAgx(GSH)14 NCs proceeds through the two electron-hopping events (2e− Au15 → 2e− (AuAg)15–17 → 4e− (AuAg)18–19 → 4e− (AuAg)18), whereas the transformation of (AuAg)18 into Au26Ag mainly involved the formation of intermediate species Au26(GSH)17Cln (n = 0–2). Moreover, we determined that the single Ag atom in Au26Ag NCs resides on the NC surface. This study not only provides a novel strategy for the synthesis of water-soluble alloy NCs but also contributes to the fundamental understanding of the alloying mechanism of metal NCs.