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

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.