Layer-by-layer assembly of three-dimensional colloidal supercrystals with tunable plasmonic properties

Area of Science:

• Materials Science
• Nanotechnology
• Plasmonics

Background:

• Synthesizing large-area, three-dimensional (3D) nanoparticle supercrystals is challenging.
• Controlling interparticle coupling in plasmonic nanostructures is crucial for tunable optical properties.

Purpose of the Study:

• To develop a simple and efficient method for synthesizing large-area 3D gold and silver nanoparticle supercrystal films.
• To investigate the plasmonic properties and coupling mechanisms within these 3D supercrystals.

Main Methods:

• Utilized layer-by-layer (LbL) assembly of Janus nanoparticles (Janus NPs) from gold or silver colloid suspensions.
• Employed thiolate passivation for nanoparticle stabilization and controlled assembly.
• Characterized the optical properties of the resulting 3D supercrystal films.

Main Results:

• Successfully synthesized large-area (>1 cm(2)) 3D gold and silver nanoparticle supercrystal films.
• Demonstrated true 3D plasmonic crystal behavior with strong transverse and longitudinal near-field coupling.
• Observed multiple longitudinal coupling modes with spectral dependence on layer number.
• Identified a universal scaling relation for longitudinal modes, attributed to a plasmonic Fabry-Perot nanocavity.
• Achieved broadband tuning of collective plasmon response (visible to near-IR).

Conclusions:

• The developed LbL assembly method using Janus NPs is effective for creating 3D plasmonic supercrystals.
• The 3D architecture enables tunable plasmonic coupling and broadband spectral response.
• This approach offers a pathway for designing advanced plasmonic metamaterials with tailored optical properties.