Fabrication and fragmentation of noble metal nanoparticles by femtosecond laser ablation: size comparison by extinction spectroscopy and microscopy

D. SCHINCA; L. SCAFFARDI; G. A. TORCHIA; P. MORENO; L. ROSO

University La Sapienza, Roma ? Italy

Conferencia; 22nd General Conference of the EPS Condensed Matter Division; 2008

University La Sapienza, Roma ? Italy

Noble metal nanoparticles fabrication and fragmentation by femtosecond laser ablation: size comparison by extinction spectroscopy and electron microscopy D. Schinca, L. Scaffardi, G. A. Torchia, P. Moreno and L. Roso 22nd General Conference of the EPS Condensed Matter Division University La Sapienza, Roma ? Italy, 25-29 August 2008             Gold and silver nanoparticles were fabricated from femtosecond (fs) laser ablation of metal targets immersed in different liquid media. Different conditions for fabrication are presented and related with particle sizes.  Gold nanoparticles were fabricated and subsecuently fragmented using the fundamental emission of a Ti:Za fs laser (800 nm). On the other hand, silver nanoparticles were fabricated and fragmented in water with the second harmonic of Ti:Za laser (400 nm) while for ethanol, a combination of fundamental and second harmonic was used.             Plasmon peak position and its full width at half maximum (FWHM) was used to analyze the UV-visible extinction spectra of the different obtained colloids and to determine the size of the produced nanoparticles.  It can be observed that, in the case of the gold, the plasmon peak shows a blue shift after fragmentation, suggesting a reduction in size. For silver, the plasmon resonance remains fixed after fragmentation, but at around 400 nm, depending on media. However its FWHM is larger than that of the non fragmented sample, also suggesting a decrease in size.                 We compare the extinction spectroscopy results with those from TEM analysis and discuss different mechanisms involved in the decrease of particle size due to fragmentation.