Open and Close-Packed, Shape-Engineered Polygonal Nanoparticle Metamolecules with Tailorable Fano Resonances

Area of Science:

• Nanotechnology
• Materials Science
• Plasmonics

Background:

• Conventional wet-chemical synthesis limits nanoparticle (NP) size, shape, and composition control.
• Achieving well-defined NPs is crucial for advanced material properties and applications.

Purpose of the Study:

• To report a top-down lithographic process for fabricating precisely engineered nanoparticles (NPs).
• To demonstrate template-assisted assembly of these NPs into ordered metamolecules with tunable properties.
• To correlate the structure of NP assemblies with their optical responses.

Main Methods:

• Utilizing top-down lithographic patterning and deposition to create nanoparticles (NPs).
• Ligating and harvesting NPs from substrates to form colloidal dispersions.
• Employing template-assisted assembly driven by capillary forces for NP organization.
• Characterizing assembled NP metamolecules and their plasmonic properties.

Main Results:

• Fabricated NPs exhibited well-defined sizes and shapes, inaccessible via wet-chemical methods.
• Template-assisted assembly produced ordered multi-NP structures (metamolecules) with controlled NP arrangement.
• Plasmonic resonances of polygonal gold NPs were correlated with metamolecule structure and optical properties.
• Close-packed assemblies with a central NP showed enhanced collective interactions and altered Fano resonances.

Conclusions:

• Top-down lithography offers superior control over NP characteristics compared to wet-chemical synthesis.
• Capillary-driven self-assembly enables precise organization of NPs into functional metamolecules.
• Structural symmetries and interparticle coupling significantly influence the optical properties of NP metamolecules.