Gold-based nanoalloys: from the laser ablation synthesis to the accurate modelling of the plasmonic properties

Alloying is a key strategy to obtain new multifunctional plasmonic materials. The combination of multiple properties in a single material and the unique features that the nanoparticles possess make this procedure intriguing and beneficial for a wide range of applications. Despite this appealing scenario, the development of high-quality plasmonic multifunctional nanoalloys poses several challenges and necessitates additional investigations. In this Thesis, particular attention is posed to the three fundamental aspects of plasmonic nanoalloys, namely their synthesis, alloying, and modeling of the optical properties, through a combined experimental and computational approach. Understanding how the variation of physicochemical parameters acts on the composition of the final alloy NPs is still a matter of debate. Here, the role of gaseous reactive species in the first stages of the laser ablation synthesis is explored to develop a more reliable synthetic method and achieve compositional control for metastable alloy nanoparticles. The problem of the alloying, intended as the formation of alloy solid solution nanoparticles rather than segregated nanostructures, is explored further by analyzing the physical and chemical parameters determining the formation of Au-Msp alloys (Msp=Al, Ga, In, and Pb). Besides, the problem of the accurate modelling and conceptual understanding of the optical properties of innovative plasmonic nanoalloys is treated. A procedure for a reliable calculation of the dielectric function in magnetic-plasmonic alloys is developed, focusing on the accurate replication of the optical properties of real Au-Co NPs colloidal samples. By addressing the problems of the synthesis of nanoalloys, their physicochemical parameters affecting the alloy formation, and the development of a reliable modelling method for their optical properties, this Thesis allows expanding the perspectives for the conscious development and exploitation of innovative plasmonic nanoalloys.