Large-Scale Synthesis, Crystal Structure, and Optical Properties of the Ag146Br2(SR)80 Nanocluster.

ABSTRACT

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-Ag146Br2(SR)80 (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 Ag51 core surrounded by a shell of Ag95Br2S80. The Ag51 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-Ag3 (triangle) and S-Ag4 (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.