Traveling through the Desalting Column Spontaneously Transforms Thiolated Ag Nanoclusters from Non luminescent to Highly Luminescent

This letter reports an unexpected observation in the purification of ultrasmall (<2 nm) thiolate-protected Ag nanoclusters (NCs) via a common separation technique (e.g., desalting column and ultrafiltration), where the nonluminescent Ag NCs were spontaneously transformed to highly luminescent NCs during the separation. This interesting finding was then used to develop a facile and fast (<5 min) synthesis method for highly luminescent Ag NCs. The key strategy was to use the separation process to selectively remove small species (e.g., salts and excess protecting ligands) from the Ag NC solution, which induced a size or structure-focusing of Ag NCs in the solution, leading to the formation of highly luminescent Ag NCs. The concurrent synthesis and purification of highly luminescent Ag NCs via a common "physical separation unit" could be further advanced in a continuous mode for large-scale production of luminescent Ag NCs.