Insights into the effect of surface ligands on the optical properties of thiolated Au25 nanoclusters.

An abnormal optical absorption at about 780 and 980 nm was observed for Au25 nanoclusters (NCs) protected by negatively charged thiolate ligands collocating with positively or neutrally charged thiolate ligands, largely due to the resultant surface charge anisotropy on the NC surface which could induce structural distortions of the thiolated Au25 NCs.