Computational approaches to the study of the electronic properties, structure and functionalization of metal nanoparticles

In this thesis, we developed and used different computational techniques to study the physicochemical properties of metal nanoparticles. We studied both bare nanoparticles and nanoparticles functionalized by organic ligands. Bare metal nanoparticles composed of two or more metal species, named nanoalloys, find application in several fields such as catalysis and plasmonics. Their physical properties crucially depend on their structure and chemical order. We developed a new global optimization algorithm to predict the lowest energy structure and chemical order of nanoalloys. We successfully applied it to the study of AgPt and AuPdPt nanoalloys. Functionalized metal nanoparticles, namely nanoparticles passivated by a shell of organic and biocompatible ligands, find applications in the biomedical field, where they are investigated and tested as diagnostic and therapeutic nanoagents. In this scenario, Au nanoparticles functionalized by thiolated molecules are a reference benchmark due to their inert, non-toxic core and controllable synthesis. In this thesis, we developed an atomistic model for the interaction between Au and S. Our potential offers the unprecedented opportunity to study, by molecular dynamics simulations with atomistic resolution, the spontaneous formation of Au-thiol bonds and the diffusion of thiols on the surface of Au nanoparticles. Our work paves the way to more realistic simulations of the synthesis of thiol-protected nanoparticles and of their interactions with the biological environment.