Colloidal Tunable Metasurfaces via Depletion-Induced Self-Assembly of Plasmonic Nanorods

Area of Science:

• Materials Science
• Nanotechnology
• Physical Chemistry

Background:

• Self-assembly is key for scalable nanostructure fabrication, especially for plasmonic materials.
• Traditional methods yield dense 3D supercrystals, limiting light and analyte access.
• 2D metasurfaces offer enhanced surface area and optical responses for sensing and photocatalysis.

Purpose of the Study:

• Introduce "colloidal metasurfaces": liquid-dispersed, reconfigurable assemblies.
• Utilize depletion-induced self-assembly (DISA) for reversible organization of plasmonic nanorods.
• Achieve dimensional control and tune optical properties of these novel assemblies.

Main Methods:

• Employed depletion-induced self-assembly (DISA) with anisotropic gold-over-silver (Au@Ag) nanorods.
• Tuned depletion strength to control assembly dimensionality (2D to 3D) and compacity (21%–80%).
• Investigated shape-dependent reconfigurability using pentagonal and square nanorods.

Main Results:

• Demonstrated reversible organization of Au@Ag nanorods into colloidal metasurfaces.
• Achieved dimensional control and modulated assembly compacity via depletion strength.
• Observed shape-dependent lattice symmetry changes (hexagonal for pentagonal rods, rhombic-to-square for square rods).
• Showcased stable optical function over multiple assembly-disassembly cycles.
• Tuned Raman scattering by altering lattice parameters.

Conclusions:

• Established a functional, reconfigurable colloidal platform for plasmonic metasurfaces.
• Highlighted the utility of shape-directed DISA for precise assembly control.
• Opened new avenues for tunable plasmonic devices in sensing and photocatalysis.