Tuning the structural and optical properties of gold/silver nano-alloys prepared by laser ablation in liquids for optical limiting, ultra-sensitive spectroscopy, and optical trapping

E. Messina, L. D’Urso, E. Fazio, C. Satriano, M.G. Donato, C. D’Andrea, O.M. Maragò, P.G. Gucciardi, G. Compagnini, F. Neri

The plasmon resonance of metallic Au/Ag nano-alloys in the colloidal state was tuned from 400 nm to 500 nm using a laser irradiated technique performed directly in the liquid state. Interesting optical nonlinearities, trapping effects and spectroscopic enhancements were detected by modifying the gold molar fraction in the nano-alloys. In particular a reduction of the limiting threshold was observed by increasing the gold amount. The SERS activity of the Au/Ag alloys was tested in liquid and in solid state in presence of linear carbon chains as probe molecules. The increased Raman signals for nanoparticles with different Au/Ag atomic ratio are presented. Finally, studies and prospects for optical and Raman tweezers experiments are discussed.

DOI