Surface Plasmon Tunability of Core-Shell Au@Mo₆ Nanoparticles by Shell Thickness Modification

Area of Science:

• Nanophotonics and Plasmonics
• Materials Science
• Surface Chemistry

Background:

• Noble metal nanoparticles exhibit plasmon resonances crucial for enhancing light-matter interactions in nanoscale systems.
• The optical properties of these nanoparticles are highly sensitive to the dielectric properties of their surrounding medium.

Purpose of the Study:

• To investigate the tunability of plasmon resonance energy in core-shell gold-molybdenum (Au@Mo₆) nanoparticles.
• To establish a correlation between the thickness of the Mo₆ shell and the plasmon resonance energy.
• To explore the potential for optical detection of this plasmonic tuning effect.

Main Methods:

• Fabrication of core-shell Au@Mo₆ nanoparticles with varying Mo₆ shell thicknesses (0-70 nm) on a fixed 100 nm gold core.
• Nanometer-resolution plasmon mapping using electron energy-loss spectroscopy (EELS) within a transmission electron microscope (TEM).
• Numerical simulations employing boundary element methods (BEM) to corroborate experimental findings.

Main Results:

• Demonstrated tunability of plasmon resonance energy from 2.4 eV to 1.6 eV by altering the Mo₆ shell thickness.
• Experimental plasmon mapping results were consistent with BEM numerical simulations.
• Simulations predicted a similar dependency for extinction energy, suggesting potential for external optical observation.

Conclusions:

• The thickness of the Mo₆ cluster shell is a critical factor in tuning the plasmon resonance energy of Au@Mo₆ nanoparticles.
• EELS provides high-resolution experimental validation of simulated plasmonic behavior.
• While optical experiments are feasible, challenges remain due to nanoparticle size distribution and scattering effects.