Miscible-Solvent-Assisted Two-Phase Synthesis of Monolayer-Ligand-Protected Metal Nanoclusters with Various Sizes.

Effective yet versatile synthetic strategies for size-tunable metal nanoclusters (NCs) are scarce. This has hampered the development of this unique class of nanomaterials. Here, a general protocol is reported for the synthesis of high-quality metal NCs protected by a variety of organic ligands (e.g., selenolate, thiolate, and phosphine) based on a miscible-solvent-assisted phase transfer between water and organic solution. This method is demonstrated to be facile, rapid (≤3 h), scalable (gram-scale), and versatile. The size of the selenolated and thiolated Au NCs can be tuned from Au10 to Au61 by simply varying the miscible solvent in proportions and types. The advantages of this method, such as quick phase separation and no need for purification treatment, enable real-time monitoring of metal NC growth within the NaBH4 reduction system. The results show that the size of Au NCs gradually increases with increasing valence electron count by a stepwise 2x e- hopping mechanism (x = 0-5), i.e., 0 e- → 2 e- → 4 e- → 8 e- → 18 e- → 22 e- → 32 e- .