Characterization after aging of Si nanoparticles synthesized by picosecond laser ablation of solids in liquids

Abstract

Colloidal silicon nanoparticle suspensions have been synthesized by the laser ablation of solids in liquids technique. We employed a picosecond laser to irradiate a silicon wafer immersed into distilled water at different fluences. After 30 months of aging, the optical properties of the nanoparticle suspensions were studied by photoluminescence spectroscopy, revealing the existence of visible light emissions arising from quantum confinement effects due to size reduction. Raman microspectroscopy was used to further observe size reduction of Si by analyzing shifts to lower frequencies of the Si-Si main vibrational mode associated to quantum confinement of phonons in silicon at nanoscale dimensions. Transmission electron microscopy measurements corroborated the presence of Si nanoparticles in the suspensions. Furthermore, the stability of these aged nanoparticles was confirmed by measuring their zeta potential. Results are analyzed and discussed in terms of the influence of the per pulse laser fluence on the nanoparticle features.