Time-Resolved Dynamics of Laser Ablation in Liquid with Gas-Evolving Additives: Toward Molding the Atomic Structure of Nonequilibrium Nanoalloys.

Laser ablation in liquid (LAL) is a reference technique for the synthesis of multicomponent non-equilibrium nanomaterials which have potentially disruptive properties in photonics, nanomedicine, and catalysis. Yet, ablation dynamics is poorly understood regarding the multielement matter and, therefore, the remarkable potential of LAL for controlling the local atomic structure of metastable nanophases remains largely unexploited. Here, the dynamics of LAL are investigated with non-equilibrium gold-iron nanoalloys generated in the presence of gas-evolving additives, which drive the formation of different nanostructures. With analytical electron microscopy, the structure in the different conditions is properly identified through complete segregation into oxide-metal heterostructures, precipitation of nanoclusters within the nanoalloys, or ordered solid solutions. To elucidate the unforeseen effects of the solutes on the atomic structure of nanoalloys, the early and full dynamics of LAL is investigated with time-resolved experiments, leading to the pivotal evidence that alloying of metastable compounds with different chemical reactivity is favored by decreasing the pressure of the shockwave front. The resulting picture indicates LAL with gas-evolving additives as a strategy for molding the atomic structure of non-equilibrium nanoalloys, opening the way to the development of a library of advanced nanomaterials otherwise inaccessible.