Glutathione-protected Au-25 clusters (Au-25@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 Au-25@GSH by changing their ligands. The temperature dependent fluorescence shows that conjugation with different ligands results in modified temperature behavior. In particular, Au-25@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 Au-25@GSH sheds new light on the future application of nanoclusters from early diagnosis towards therapeutics. (C) 2012 Published by Elsevier Inc.