Macroscopic Synthesis of Ligand-Free Subnanometer Metal Clusters via Molten Salt

Macroscopic synthesis of bare metal nanoclusters is aprerequisitefor their practical applications from laboratory to industry. Herein,we reported an unexpected high dissolution of copper in molten LiCl-KCleutectic salt. Combining synchrotron-based spectroscopy, nuclear magneticresonance, and scanning transmission electron microscopy measurements,the dissolved copper was demonstrated to form nanoclusters with afew atoms in the molten salt, which can be frozen to maintain theirpristine states for more than one year. The theoretical analysis indicatedthat the salt ions formed a protective solvation shell to hold thestability of nanoclusters. By washing the one-pot solidified saltwith water, the macroscale of ligand-free subnanometer copper clustersis obtained. With this method, the preparation of metal nanoclusterscan be further scaled up at low cost to speed up the fundamental researchand industrial applications.