The enhancement of electron–phonon coupling in glutathione-protected Au25 clusters

[Display omitted] •We modify Au25@GSH with mercaptosuccinic acid and propanoic acid ligands.•Au25 cluster with ligands shows different temperature behavior.•A proper ligand can enhance the electron–phonon coupling of Au25 cluster.•Ligand-modified Au25 cluster can be applied in bioimaging, biosensing, and therapy. Glutathione-protected Au25 clusters (Au25@GSH) are prospective for biological applications due to their biocompatibility and near infrared fluorescence. The weak electron–phonon coupling, however, restricts their applications in bioanalysis and therapeutics. Here we modify the properties of Au25@GSH by changing their ligands. The temperature dependent fluorescence shows that conjugation with different ligands results in modified temperature behavior. In particular, Au25@GSH-MPA evidently exhibits enhanced phonon coupling, therefore, resulting in a decrease in the emission energy and an increase in bandwidth upon increasing temperatures. The enhanced phonon coupling in modified Au25@GSH sheds new light on the future application of nanoclusters from early diagnosis towards therapeutics.