Size tunable Au@Ag core-shell nanoparticles: synthesis and surface-enhanced Raman scattering properties

Area of Science:

• Nanotechnology
• Materials Science
• Physical Chemistry

Background:

• Gold-silver core-shell nanoparticles (Au@Ag NPs) offer unique optical and plasmonic properties.
• Controlling the size and composition of Au@Ag NPs is crucial for optimizing their performance.

Purpose of the Study:

• To develop a simple and efficient aqueous synthesis method for size-tunable Au@Ag core-shell nanoparticles.
• To investigate the optical and surface-enhanced Raman scattering (SERS) properties of these synthesized nanoparticles.

Main Methods:

• Aqueous synthesis of Au@Ag core-shell nanoparticles via stepwise silver reduction on preformed gold nanoparticles.
• Size modulation by controlling silver shell thickness or gold core size.
• Characterization of optical properties using Mie extinction calculations.
• Evaluation of SERS enhancement using three different laser lines (532, 633, and 785 nm).

Main Results:

• Stable, uniform, and size-tunable Au@Ag core-shell nanoparticles (30-110 nm) were synthesized.
• Optical properties of Au@Ag NPs resemble those of silver nanoparticles of similar sizes.
• Au@Ag core-shell NPs exhibit higher SERS efficiency than silver nanoparticles, especially under near-infrared excitation.

Conclusions:

• The developed method allows for controlled synthesis of Au@Ag core-shell NPs with tunable optical properties.
• These Au@Ag NPs demonstrate superior SERS enhancement compared to Ag NPs, particularly at longer wavelengths.
• The findings provide a basis for selecting optimal Au@Ag NPs for SERS-based analytical and bioimaging applications.