Molecule-like and lattice vibrations in metal clusters.

Area of Science:

• Materials Science
• Spectroscopy
• Nanotechnology

Background:

• Atomically precise metal clusters exhibit unique electronic and optical properties.
• Understanding their vibrational dynamics is crucial for predicting and controlling their behavior.
• Ligand protection significantly influences the properties of metal clusters.

Purpose of the Study:

• To investigate the vibrational signatures of various ligand-protected noble metal clusters.
• To differentiate between molecule-like and lattice (breathing) vibrational modes.
• To explore the influence of metal composition and ligands on vibrational properties.

Main Methods:

• Low-temperature Raman spectroscopy was employed to measure vibrational spectra.
• Density Functional Theory (DFT) calculations were used for detailed band analysis.
• A series of gold (Au) and silver (Ag) clusters with different ligands were studied.

Main Results:

• Distinct Raman spectra were obtained for Au25(SR)18, Ag25(SR)18, Ag24Au1(SR)18, Ag29(S2R)12, and Ag44(SR)30 clusters.
• Low-frequency bands correspond to metal core vibrations, while higher-frequency bands relate to metal-ligand interface structures.
• A unique breathing vibrational mode was identified for each cluster, sensitive to changes in metal atoms and ligands.

Conclusions:

• Low-frequency Raman spectroscopy is a powerful tool for characterizing atomically precise, molecule-like particles.
• A simple lattice dynamics model is insufficient to fully describe the vibrational properties of these clusters.
• The findings provide insights into the vibrational dynamics of nanomaterials like nanocarbons, quantum dots, and perovskites.