Mapping bright and dark modes in gold nanoparticle chains using electron energy loss spectroscopy

Area of Science:

• Nanoscience and Nanotechnology
• Materials Science
• Spectroscopy

Background:

• Gold nanostructures exhibit unique optical and electronic properties due to surface plasmon resonances.
• Understanding plasmon modes in ordered nanostructures is crucial for developing advanced optical devices.

Purpose of the Study:

• To investigate the plasmon modes in gold nanosphere chains of varying lengths using STEM-EELS.
• To characterize the energy evolution and detectability of these plasmon modes as a function of chain length.

Main Methods:

• Utilized scanning transmission electron microscopy-electron energy loss spectroscopy (STEM-EELS) for high-resolution analysis.
• Employed EELS mapping to identify and localize specific plasmon modes.
• Investigated gold nanosphere chains ranging from 1 to 5 particles.

Main Results:

• Identified distinct energy-loss peaks corresponding to plasmon modes (l=1-5) in gold nanosphere chains.
• Observed that longer chains accommodate more observable plasmon modes.
• Demonstrated that mode energies shift and delocalize along the chain as length increases, with new modes becoming the highest energy.
• Found that higher-order modes become less detectable with increasing chain length.

Conclusions:

• STEM-EELS is effective for characterizing plasmon modes in nanoscale assemblies.
• The number and energy of plasmon modes in gold nanosphere chains are strongly dependent on chain length.
• The findings provide insights into the fundamental plasmon physics of one-dimensional nanostructures.