Cu-Ag core-shell nanoparticles: A direct correlation between micro-Raman and electron microscopy

Vibration modes of metal core-shell nanoparticles have been measured by confocal micro-Raman spectroscopy. Compared to a standard macroscopic scale, the number of analyzed nanoparticles is reduced to ${10}^{3}--{10}^{4}$. We observed two distinct contributions in the same Raman spectrum originating from Cu-Ag core-shell and pure Ag nanoparticles. The nanoparticle sizes are calculated and successfully compared to the ones obtained by electron microscopy on the same micron-scale area. The bond matching between Cu core and Ag shell is pointed out from a conjugated Raman and transmission electron microscopy study.