Multiple synthesis routes for atomically precise noble metal nanoclusters

Well-defined metal nanoclusters protected by thiolates, with sizes between nanocrystals and metal atoms, have attracted enormous attention due to their various structures, controllable compositions, intriguing physical and chemical properties, and potential applications. Atomically precise metal nanoclusters are a type of important nanomaterial that can provide an ideal platform to address some key challenges related to their applications. However, compared to the straightforward synthesis of larger nanoparticles, the preparation of ultra-small metal nanoclusters frequently encounters difficulties owing to the pursuit of monodispersity and atomic accuracy. Although a series of effective synthesis methods have been developed for metal nanoclusters with well-defined sizes, structures and compositions, rational design and successful preparation of atomically precise metal nanoclusters still face challenges that further hinder the enrichment of cluster libraries and the in-depth understanding of structure–property relationships. In this review, we summarize some recent advances in strategies for the synthesis of atomically precise metal nanoclusters, in particular, silver and gold nanoclusters as well as alloy nanoclusters, and emphasize the following synthesis methods including the Brust–Schiffrin method, ligand-exchange, galvanic/anti-galvanic reaction, etching, solid phase synthesis and intercluster reaction.