Confined Unimolecular Micelles for Precisely Controlled in Situ Synthesis of Stable Ultrasmall Metal Nanocluster Assemblies

Ultrasmall noble metal nanoclusters (NCs; core size, <2 nm) with a high surface atomic ratio and a tunable electronic structure have attracted intensive interest; however, the controlled preparation of stable metal NC assemblies is still a challenge. Here, star-like diblock copolymer unimolecular micelles were used as a universal and robust scaffold to synthesize ultrasmall metal NC assemblies with a controlled size and amount of metal NCs (10-160). The size of the NC assemblies can also be controlled by changing the length of the P4VP block of the star-like polymers via atom transfer radical polymerization. The thiolate ligands play an important role in the control of the size of individual nanoclusters and largely enhance the stability of the NC assemblies. The as-synthesized stable ultrasmall metal NC assemblies will have broad application prospects in the fields of catalysis, optics, and biomedicine.