In Liquid Laser Processes for Metal Nanoparticles Synthesis and Manipulation

The exponential spread of high level technology in the last decade has been followed by an increasing request for new materials able to fulfill all required characteristics for the construction of smaller devices. In this view, nanostructures and in particular metal nanoparticles are gaining attention since their unique optical, electrical and antibacterial properties. Pulsed Laser Ablation in Liquid represents a consolidated route for the synthesis of pure surface metal nanoclusters but, till now, the low production yield of this technique has stopped every attempt in this direction. For these reasons, the development of new strategies to enhance the amount of ablated material represents an interesting field of research. In particular, it has been studied how the ablation of a metal wire in a water flow chamber can lead to an increase of the productivity with respect to bulk ablation and a strong dependence of efficiency on the wire thickness and laser parameters has been noted. A model to describe this behaviour has been proposed, with considerations about heat loss phenomena, reflectivity of the wire surface and cavitation bubble mechanism. Laser fabricated nanoparticles have been also used for the preparation of different nanocomposites in order to tune their properties. Spontaneous and induced aggregation phenomena of noble metal nanoparticles have been studied, with regard to their influence on the Surface Plasmon Resonance variations. It is also possible to combine single metal colloidal solution for obtaining mixed metal nanoparticles with unique features. For this reason, Au/Ni mixed systems have been produced by laser mixing in liquid environment and characterized by spectroscopic and morphological techniques. The mechanism of their formation has been explained on the base of the laser irradiation environment conditions.