Making copper, silver and gold fullerene cages breathe

Area of Science:

• Computational chemistry
• Materials science
• Nanophotonics

Background:

• Fullerene structures are crucial in nanomaterials.
• Understanding their optical properties is key for applications.
• Dynamic changes in fullerene size can affect their electronic and optical behavior.

Purpose of the Study:

• To investigate the impact of fullerene inflation and deflation on the optical properties of Au32, Cu32, and Ag32 nanoparticles.
• To compare the observed optical spectrum changes with the ground-state Highest Occupied Molecular Orbital-Lowest Unoccupied Molecular Orbital (HOMO-LUMO) gap.
• To analyze the dynamic behavior of these metallic nanoparticles under size variation.

Main Methods:

• Classical approach using the Green's dyadic method to study extinction spectra.
• Real-time time-dependent density functional theory (TD-DFT) for optical spectrum calculations.
• Delta-kick (δ-kick) simulations to analyze dynamic responses.

Main Results:

• Significant differences in extinction spectra were observed for Au32, Cu32, and Ag32 during size changes.
• A red-shift in optical properties was noted as fullerenes inflated, with a notable 0.8 eV shift in the first peak for gold nanoparticles.
• Silver nanoparticles exhibited smoother behavior compared to gold and copper.
• Changes in optical spectra could not be directly correlated with alterations in the HOMO-LUMO gap.

Conclusions:

• The optical properties of metallic fullerenes are sensitive to dynamic size changes (breathing).
• Gold nanoparticles show pronounced spectral shifts upon inflation, while silver exhibits more stable behavior.
• The relationship between optical spectral changes and the HOMO-LUMO gap is complex and not a direct proportionality.