Growth Dynamics of Colloidal Silver-Gold Core-Shell Nanoparticles Studied by In Situ Second Harmonic Generation and...

Area of Science:

• Colloidal chemistry
• Nanomaterials science
• Surface science

Background:

• Colloidal silver-gold core-shell (Ag@Au CS) nanoparticles are crucial for plasmonic applications.
• Understanding their in situ growth dynamics is essential for controlled synthesis and enhanced properties.

Purpose of the Study:

• To monitor the in situ growth dynamics of Ag@Au CS nanoparticles during stepwise synthesis.
• To correlate surface morphology evolution with optical properties and plasmonic behavior.

Main Methods:

• Stepwise synthesis of Ag@Au CS nanoparticles in water.
• Time-dependent second harmonic generation (SHG) and extinction spectroscopy for in situ monitoring.
• Transmission electron microscopy (TEM) for surface morphology analysis.
• Finite-difference time-domain (FDTD) calculations for spectral comparison.

Main Results:

• Sequential additions of reagents led to a progressive growth of the gold shell, transforming the surface from urchin-like to smooth and uniform.
• Extinction spectra showed deviations from FDTD calculations in early stages due to surface roughness, with improved agreement after the final addition.
• In situ SHG signals provided insights into growth time scales, primarily reflecting surface morphology changes.

Conclusions:

• The combined spectroscopic and computational approach offers a detailed understanding of colloidal nanoparticle growth mechanisms.
• This study lays a foundation for developing advanced plasmonic nanomaterials with tailored properties.