Large-Scale Synthesis, Crystal Structure, and Optical Properties of the AgBr(SR) Nanocluster.

Solving the atomic structure of large-sized metal nanoclusters is a highly challenging task yet critically important for understanding the properties and developing applications. Herein, we report a stable silver nanocluster-AgBr(SR) (where SR = 4-isopropylbenzenethiolate)-with its structure solved by X-ray crystallography. Gram-scale synthesis with high yield has been achieved by a one-pot reaction, which offers opportunities for functionalization and applications. This silver nanocluster possesses a core-shell structure with a Ag core surrounded by a shell of AgBrS. The Ag core can be viewed as a distorted decahedron, endowing this nanocluster with quantized electronic transitions. In the surface-protecting layer, five different types of S-Ag coordination modes are observed, ranging from the linear Ag-S-Ag to S-Ag (triangle) and S-Ag (square). Furthermore, temperature-dependent optical absorption and ultrafast electron dynamics are conducted to explore the relationship between the properties and structure, demonstrating that the distorted metal core and "flying saucer"-like shape of this nanocluster have significant effects on the electronic behavior. A comparison with multiple sizes of Ag nanoclusters also provides some insights into the evolution from molecular to metallic behavior.