Here, the synthesis of water-dispersible naked gold nanoclusters (AuNC ) is reported by a simple reduction of HAuCl with NaOH at room temperature, and it is shown that they are non-luminescent. They are then easily passivated with different thiols and adenosine monophosphate, leading to luminescent NCs. This is an important finding because the photoluminescence of the passivated NCs can now be clearly attributed to the ligand-AuNC surface interaction. These results are also highly relevant from the point of view of the preparation of luminescent NCs from the same NC batch. This strategy can be valuable for the preparation of a broad range of nano(bio)composites.

A water-dispersible, biocompatible, fluorescent ratiometric pH nanosensor over a broad pH range is reported.