Plasmonic properties and sizing of core-shell Cu-Cu2O nanoparticles fabricated by femtosecond laser ablation in liquids

SANTILLÁN, JESICA MARÍA JOSÉ; VIDELA, FABIÁN ALFREDO; SCHINCA, DANIEL CARLOS; SCAFFARDI, LUCÍA BEATRÍZ

San Diego, California

Conferencia; SPIE OPTICS + PHOTONICS: "NANOSCIENCE + ENGINNEERING"; 2012

SPIE

The synthesis and study of optical properties of copper nanoparticles are of great interest since they are applicable to different areas such as catalysis, lubrication, conductive thin films and nanofluids. Their optical properties are governed by the characteristics of the dielectric function of the metal, its size and environment. The study of the dielectric function with radius is carried out through the contribution of free and bound electrons. The first one is corrected for size using the modification of the damping constant. The second one takes into consideration the contribution of the interband transitions from the d-band to the conduction band, considering the larger spacing between electronic energy levels as the particle decreases in size below 2 nm. Taking into account these specific modifications, it was possible to fit the bulk complex dielectric function, and consequently, determine optical parameters and band energy values such as the coefficient for bound electron contribution Qbulk = 2 x 1024, gap energy Eg = 1.95 eV, Fermi energy EF = 2.15 eV and damping constant for bound electrons gb = 1.15 x 1014 Hz. The fit of the experimental extinction spectra of the colloids obtained by ultrashort pulse laser ablation of solid target in liquids, reveals that the nanoparticles have a core-shell structures formed by a Cu core and a Cu2O shell, due to an oxidation reaction during the fabrication process. The results suggest that the larger fluences enhances an increase of shell thickness as well as a reduction in the core radius.