Binary Chiral Nanoparticles Exhibit Amplified Optical Activity and Enhanced Refractive Index Sensitivity

Area of Science:

• Nanotechnology and Materials Science
• Chirality and Optical Activity
• Plasmonics

Background:

• Metallic chiral nanoparticles (CNPs) possess inherent chirality, making them suitable for enantiomer-related applications.
• Sub-10 nm helical pitch in CNPs leads to weak optical activity (OA), limiting their practical development.
• Existing CNPs require enhanced optical properties for broader applications in chiral technologies.

Purpose of the Study:

• To devise a facile method for amplifying the optical activity of metallic chiral nanoparticles.
• To investigate the effect of alloying on the plasmonic properties and optical activity of CNPs.
• To explore the potential of enhanced CNPs in various chirality-dependent applications.

Main Methods:

• A three-step layer-by-layer glancing angle deposition (GLAD) method was employed.
• Host CNPs were alloyed with various metals (Cu, Au, Al, Fe) to create binary alloy CNPs.
• The GLAD-induced heating effect facilitated solute metal diffusion and alloy formation.

Main Results:

• Chiral alloying successfully amplified the plasmonic optical activity of both host and solute metallic nanoparticles.
• Alloying Ag CNPs with Cu, Au, Al, and Fe, and Cu CNPs with Ag demonstrated significant OA enhancement.
• The resulting alloy CNPs exhibited enhanced refractive index sensitivity.

Conclusions:

• The developed chiral alloying method effectively amplifies the optical activity of metallic CNPs.
• Enhanced alloy CNPs show improved optical properties and sensitivity, broadening their application scope.
• These findings pave the way for advanced applications in asymmetric catalysis, enantioseparation, biosensing, and bioimaging.