posted on 2019-08-06, 16:14authored byXi Kang, Hadi Abroshan, Shuxin Wang, Manzhou Zhu
Metal
nanoclusters have attracted extensive interests owing to their atomically
precise structures as well as intriguing properties. However, silver
nanoclusters are not as stable as their gold counterparts, impeding
the practical applications of Ag nanoclusters. In this work, a strategy
of free valence electron centralization was exploited to render parent
Ag nanoclusters highly stable. The stability of Ag29(SSR)12(PPh3)4 (SSR: benzene-1,3-dithiol)
was controllably enhanced by stepwisely alloying the Ag29 nanocluster to Ag17Cu12(SSR)12(PPh3)4 and Au1Ag16Cu12(SSR)12(PPh3)4. Specifically,
the trimetallic Au1Ag16Cu12 is ultrastable
even at 175 °C, which is close to the nanocluster decomposition
temperature. The structures of Ag17Cu12 and
Au1Ag16Cu12 nanoclusters are determined
by single-crystal X-ray diffraction. Furthermore, a combination of
X-ray photoelectron spectroscopy measurements and density functional
theory calculations demonstrates that the enhanced stability is induced
by the centralization of the free valence electrons to the interior
of the nanocluster. More importantly, the Au1Ag16Cu12 enables the multicomponent A3 coupling
reaction at high temperatures, which remarkably shortens the catalytic
reaction time from ∼5 h to 3 min. Overall, this work presents
a strategy for enhancing the thermal stability of nanoclusters via
centralizing the free valence electrons to the nanocluster kernels.