Crystalline-Amorphous Heterostructure: A Novel Configuration for Silver Nanoclusters.

Heterostructured composite materials with multiple components have potential applications in diverse aspects, as they tend to exhibit superior physicochemical properties than the sum of their single counterparts. However, the fabrication of heterostructures composed of atomic-precise metal nanoclusters (NCs) is seldom reported owing to their inherent instability, leading to the decomposition of metal NCs during the formation of peripheral layers. Here, a spontaneously formed amorphous-crystalline heterostructured Ag@Ag is discovered, wherein the amorphous Ag NCs are enveloped by a single crystal of Ag NCs. The formation of Ag@Ag involves three stages, including initial crystallization of Ag NCs, partial decomposition (self-sacrifice) of Ag NCs enabling Ag assembly, and epitaxial-growth crystallization of the Ag NCs. The partially decomposed Ag NCs provide starting materials for the formation and crystallization of Ag NCs to encapsulate the Ag seeds, while the residual Ag loses its crystallinity in solution simultaneously. This work not only reports a novel class of heterostructured materials for the first time but also provides new insights into the macroscopic co-assembly of distinct silver clusters.