Layer-by-layer alloying of NIR-II emissive M50 (Au/Ag/Cu) superatomic nanocluster

The intermetallic synergy plays a critical role in exploring the chemical-physical properties of metal nanoclusters. However, the controlled doping or layer-by-layer alloying of atom-precise metal nanoclusters (NCs) has long been a challenging pursuit. In this work, two novel alloy nanoclusters [PPh4]4[Ag32Cu18(PFBT)36] ((AgCu)50) and [PPh4]4[Au12Ag20Cu18(PFBT)36] (Au12(AgCu)38), where PFBT is pentafluorobenzenethiolate, with shell-by-shell configuration of M12@Ag20@Cu18(PFBT)36 (M = Ag/Au) were synthesized by a facile one-pot co-reduction method. Notably, a fingerprint library of [Ag50−xCux(PFBT)36]4− (x = 0 to 50) from Ag50 to Cu50 has been successfully established as revealed by electrospray ionization mass spectrometry. Single-crystal X-ray diffraction analysis of trimetallic Au12(AgCu)38 confirmed the layer-by-layer alloying under reducing conditions. What is more, (AgCu)50 and Au12(AgCu)38 both show broad photoluminescence (PL) peak in the second near-infrared (NIR-II) window, and the Au doping in the innermost shell considerably enhances the photoluminescence intensity. This work not only offers an insight in the process of metal cluster alloying but also provides a platform to study the doping-directed PL properties in the multimetallic cluster system.