Shell engineering to achieve modification and assembly of atomically-precise silver clusters

Continuing research on the preparation and structural determination of monolayer-protected silver clusters has been performed. The compounds include mixed-valence Ag0/1+ clusters and single-valence Ag1+ clusters, which contain a few to tens or hundreds of Ag atoms that are protected by organic ligands. Sometimes, counter ions and extraneous species appear in their crystalline state. These non-metal parts define the shell layers of silver clusters. Strong coordination bonds and weak supramolecular interactions have been employed not only to modify the shell configurations and components of discrete silver clusters but also to hierarchically assemble silver clusters, producing novel cluster-based functional materials with unexpected physical and chemical properties. Atomically-precise structures help to map out definite electronic structures and structure-property correlations, enabling precise control of shell layers to achieve desired stability and specific functionalities. In this Tutorial Review, based on classic silver cluster paradigms, we first summarize the strategies and recent advances in precise modification and hierarchical assembly of well-defined silver clusters through shell engineering. Second, the correlations of structure-property and structure-functionality are summarized. Of these, the most important is structure-luminescence relationship, which is discussed in detail. In this topic, the uniqueness and prospect of silver clusters as potential lighting materials are scrutinized. Finally, the existing challenges and perspectives of functional silver clusters are presented. The general strategic design presented in this Review will motivate researchers to exploit the development of functionality-oriented materials based on nanosized building blocks in the enrichment of nanotechnology and material science.