Insight into the Mechanism of Single-Metal-Atom Tailoring on the Surface of Au-Cu Alloy Nanoclusters.

Tailoring the surface structure of nanomaterials is desirable for investigating their mechanisms and properties from a nanochemistry perspective. The modification of the surface of metal nanoparticles with a single metal atom has proven difficult, which has hindered the understanding of the contribution of different motifs in nanoclusters to their properties. Herein, we report single-metal-atom surface tailoring by thermally etching the nanocluster Au x Cu 15- x (DPPMH) 3 (SPhCl 2 ) 9 ( x = 8 or 9) to obtain Au x Cu 16- x (DPPMH) 2 (DPPM)(SPhCl 2 ) 9 ( x = 9 or 10) nanoclusters. An Au 7 Cu 4 core was observed in both nanoclusters, which can be regarded as part of an icosahedron. Experiments and theoretical simulations revealed the tailoring processes of the icosahedron. Both nanoclusters displayed an NIR-II emission, and the introduction of the surface metal atom led to a red-shift in the emission band from 983 to 1025 nm. This work contributes to the development of precisely tailored nanocluster structures and provides an understanding of structure-property correlations.