Coherent Vibrational Dynamics of Au₁₄₄(SC₈H₉)₆₀ Nanoclusters

Abstract

The coherent vibrational dynamics of Au 144 (SC 8 H 9 ) 60 , obtained from femtosecond time-resolved transient absorption spectroscopy, are described. Two acoustic modes were identified and assigned, including 2.0 THz breathing and 0.7 THz quadrupolar vibrations. These assignments are consistent with predictions using classical mechanics models, indicating that bulk models accurately describe the vibrational properties of Au 144 (SC 8 H 9 ) 60 . Coherent phonon signals were persistent for up to 3 ps, indicating energy dissipation by the nanocluster was the primary dephasing channel. The initial excitation phases of the breathing and quadrupolar modes were π-phase-shifted, reflecting differences in the displacive nuclear motion of the vibrations. The combined agreement of the vibrational frequencies, relative phases, and decoherence times supported predictions based on classical models. The vibrational frequencies were insensitive to silver substitution for gold but did show increased inhomogeneous damping of the coherent phonons. The ability to predict the vibrational properties of metal nanoclusters can have an impact on nanoresonator and mass sensing technologies.

Robust vibrational coherence protected by a core–shell structure in silver nanoclusters

“… 59 Recently, significant coherent vibrations were reported in Au 144 (SR) 60 (ref. 61 ) (Au 144 for short) NCs with an icosahedral Au 12 core protected by two layer gold shells (Au 42 and Au 60 ). 22 Au 144 exhibits similar vibration frequencies as those of [Au 25 (SR) 18 ] − , while the damping was relatively slower.…”

Nanocluster Chemistry and the Role of in Situ Fluorescence as an Analytical Tool

“…The following equation was proposed: n * = italicN V A − italicM − italicz where the electron count ( n* ) is particularly stable with electron configurations corresponding to one of the magic numbers for closed shell electron counts, N VA is the product of the number of metal atoms and the valence electron count (i.e., 1 per atom for Au or Ag atom, 0 per atom for Pt or Pd, and so on), M is the number of electron localizing ligands (assuming 1e–/ligand), and z is the charge of the cluster. From this original work, theoretical models for understanding and predicting stable structures of MNCs have since developed significantly, now capable of modeling thousands of MNC structures and accurately predicting absorbance spectra, reactivity of clusters, ligand organization, and even excited state dynamics. − …”

Influence of Halogen–Solvent Hydrogen Bonding on Gold Nanocluster Photoluminescence

“…Subnanometer to few-nanometer metal nanoclusters exhibit optical, electronic, and mechanical properties that are distinct from those of even slightly larger plasmonic nanoparticles. − These systems’ unique characteristics and high degree of structural precision provide opportunities to tailor energy-transfer pathways and efficiencies. As a result, structurally precise nanoclusters can impact applications such as photodynamic therapy, manufacturing of materials, mass sensing, optical tagging, photonic integrated circuits, quantum emitters, etc.…”