Optical Extinction of Core-Shell Metal Nanoparticles Generated by fs Laser Ablation. Analysis of Free and Bound Electron Contribution to Plasmonic Properties

F. A. VIDELA; J. M. J. SANTILLÁN; D. C. SCHINCA ; L. B. SCAFFARDI

La Plata

Congreso; II EULASUR Summer School, 4-9 september 2011; 2011

Centro de Investigaciones Ópticas, CIOp

Optical Extinction of Core-Shell Metal Nanoparticles Generated by fs Laser Ablation. Analysis of Free and Bound Electron Contribution to Plasmonic Properties.  F. A. Videla1,2, J. M. J. Santillán1, D. C. Schinca1,2 y L. B. Scaffardi1,2 1Centro de Investigaciones Ópticas (CIOp), (CONICET La Plata - CIC), La Plata, Argentine. 2Área Departamental de Ciencias Básicas, Facultad de Ingeniería, UNLP, La Plata, Argenine.    The study of metal nanoparticles is of great interest due to their applications in catalysis, biomedicine, metalmechanics, conductive thin films and microfluids. The properties of the nanoparticles required for these applications are dependent on the size and shape of the particle. Laser ablation of solid targets in liquids is a simple and straightforward method to generate this kind of nanoparticles that, in general, show a core-shell structure. In this paper we particularly analyze and characterize the size of core-shell copper nanoparticles (Cu-Cu2O) obtained by ultrafast laser ablation, through the study of their extinction spectra in the UV-Vis-NIR part of the spectrum. The plasmonic properties of these nanoparticles rely on the dependence of the metal dielectric function with size and, in turn, with free and bound electrons dynamics that may affect extinction response. Using a suitable expression for the dielectric function, we simulate extinction spectra of spherical core-shell structures of SiO2-Cu for wavelengths between 300 and 2500 nm, for different radii in the range between 10 to 50 nm. It is shown that the IR shift of the plasmon peak is inversely proportional to the thickness, similarly other dielectric core-noble metal shell.