Au 10 Ag 17 (TPP) 10 (SR) 6 Cl 5 nanocluster: structure, transformation and the origin of its photoluminescence.

Nanocluster photoluminescence (PL) has important practical applications and its rationalization is therefore of significant interest. Here, we report the synthesis, structure determination and photoluminescence of Au 10 Ag 17 (TPP) 10 (SR) 6 Cl 5 (TPP = triphenylphosphine, SR = 3, 5-bis(trifluoromethyl)thiophenol, denoted as Au10Ag17). Au10Ag17 exhibited a low photoluminescence quantum yield (PLQY) of 2.8%, which could be increased 15-fold by removing the two terminal silver atoms to give Ag x Au 25- x (SR) 5 (TPP) 10 Cl 2 2+ ( x = 11-13, SR = 2-phenylethylmercaptan, abbrev. Au12Ag13). The discovery of such a PL switch constitutes an interesting opportunity to further understand the origin of fluorescence in nanoclusters.