VIBRATIONNAL PROPERTIES OF SELF ORGANISED COBALT NANOPARTICLES AND CORE-SHELL COBALT/COBALT OXIDE NANOPARTICLES
Résumé
Cobalt nanoparticles properties differ from bulk counterparts and Raman spectroscopy is a powerful tool to access structural information at chemical bond scale. We synthetized monodisperse cobalt nanoparticles of various sizes using chemical reduction approach [1]. Due to monodispersity and stability against oxidation particles were self-organized in superlattices. Thanks to high throughput Raman system we report first observation of low wavenumber Raman scattering from cobalt nanoparticles under visible laser excitation, far from any surface plasmon resonance [2]. We assigned Raman signature of the nanoparticles, according to Lamb’s elastic sphere model and we demonstrate that Raman scattering is an alternative technique to access size distribution.
Infrared and Raman spectra were also performed and indicated that coating agent is covalently bonded to cobalt nanoparticles.
We also report infrared and Raman spectra from core/shell, cobalt/cobalt oxide samples. We will discuss stability of such structure against laser excitation (figure 1). Finally we carefully studied Raman signature versus excitation wavelength and highlighted resonance effect.