Resonant Raman Scattering by quadrupolar vibrations of Ni-Ag Core-shell Nanoparticles

TL;DR

This study investigates low-frequency resonant Raman scattering in Ni-Ag core-shell nanoparticles, revealing that silver's electron contribution dominates the plasmon excitation and confirming a loosely bonded core-shell structure.

Contribution

It provides experimental evidence of quadrupolar vibrational modes in Ni-Ag core-shell nanoparticles and clarifies the role of silver electrons in resonant Raman scattering.

Findings

Resonant enhancement occurs when excitation matches surface dipolar modes.

Raman scattering is mainly influenced by silver electron contribution.

Nanoparticles have a core-shell structure with loosely bonded silver shell.

Abstract

Low-frequency Raman scattering experiments have been performed on thin films consisting of nickel-silver composite nanoparticles embedded in alumina matrix. It is observed that the Raman scattering by the quadrupolar modes, strongly enhanced when the light excitation is resonant with the surface dipolar excitation, is mainly governed by the silver electron contribution to the plasmon excitation. The Raman results are in agreement with a core-shell structure of the nanoparticles, the silver shell being loosely bonded to the nickel core.