Close-packed two-dimensional silver nanoparticle arrays: quadrupolar and dipolar surface plasmon resonance coupling

Area of Science:

• Materials Science
• Nanotechnology
• Plasmonics

Background:

• Silver nanoparticles (AgNPs) are crucial in plasmonics due to their unique optical properties.
• Controlling nanoparticle arrangement is key to tailoring their collective plasmonic behavior.

Purpose of the Study:

• To develop a method for creating homogeneous 2D silver nanoparticle arrays.
• To investigate the plasmonic properties of these arrays and their dependence on interparticle spacing.

Main Methods:

• Synthesis of homogeneous silver nanoparticles (40–100 nm) via an improved seed-mediated method.
• Fabrication of 2D AgNP arrays at an oil/water interface using 3-mercaptopropyltrimethoxysilane for controlled spacing.
• Embedding arrays in polydimethylsiloxane and applying biaxial stretching to tune interparticle distances.
• Characterization of plasmonic properties and comparison with finite difference time domain (FDTD) simulations.

Main Results:

• Homogeneous 2D AgNP arrays exhibited strong quadrupolar cooperative plasmon resonance and a red-shifted dipolar mode.
• Tuning interparticle distance via biaxial stretching modulated both quadrupolar and dipolar couplings.
• Increased interparticle distance led to decreased quadrupolar resonance intensity and disappearance of dipolar coupling.
• Experimental results showed qualitative agreement with FDTD simulations of local electric fields.

Conclusions:

• The study successfully demonstrates the fabrication of tunable 2D AgNP arrays with controllable plasmonic responses.
• The findings highlight the significant influence of interparticle coupling on the optical properties of AgNP arrays.
• This work provides a foundation for designing advanced plasmonic devices with tailored optical characteristics.