Fs laser pulses for ablation and deposition of noble metal nanoparticles with tunable optical properties

Full text: The capability of generating nanoparticles by direct ablation of metals through the use of fs laser pulses has been widely confirmed, during the last years, both theoretically and experimentally. The process is characterized by a large fraction of nanoparticles which, as reported by Tsakiris et al. can be in the range of 90% of the ablated material. In the work here presented the tunability of Au, Ag and Cu core nanoparticles generated by a 800 nm, 120 fs Ti:Sa laser in different vacuum conditions is reported. Uv-vis, XRD, XPS, TEM and SEM techniques have been used in order to characterize the obtained deposits. The outcome display promising perspectives in controlling the tunability of the plasmonic features by varying the experimental conditions employed. With this regard the role played by nanoparticles' distribution, coalescence and growth seems to be fundamental in determining the optical properties observed. The presence of nanoparticle shell structures, especially for Cu where Cu₂O can be considered the most probable species to be formed, do not determine the final properties of the deposit where, instead, the collective noble metal core nanoparticle characteristics play a major role. The comparison among results obtained by the three noble metals highlight how simple experimental parameters changes can tune the plasmonic properties of the nanoparticles generated by fs laser ablation and provide straightforward benefits for potential optical applications. (author)