Micron- and nano-sized particles of Ga-based liquid metals (LMs) are an interesting class of materials with fascinating properties deriving from their simultaneous metallic and liquid nature. In addition to the chemical composition of the bulk, the self-passivating gallium oxide skin of Ga-based particles has unique viscoelasticity and plays a crucial role in determining their chemical and mechanical behavior, including their wetting and undercooling properties as well as electrical conductivity. These chameleon metals have applications as soft and fluid conductors in electronic and optical devices, in microfluidics and in robotics, and offer unique opportunities in catalysis, drug delivery and batteries. Yet, not much is known about their reactivity at the nanoscale and whether this one is affected by the presence and thickness of their native oxide skin.<br/>In this talk, I will present two studies in which we explored the impact of capping ligands on the surface properties of Ga nanoparticles (NPs) and their reactivity towards a copper molecular precursor. First, I will demonstrate that a galvanic replacement reaction (GRR) takes place between Ga NPs and a copper-amine complex to form anisotropic Cu-Ga nanodimers. We attribute the unusual final morphology to the liquid nature of Ga NPs and the element segregation to the presence of the oxide shell. The latter led us to explore the effect that the chemistry of the capping ligand can have on the oxide thickness of Ga NPs and how their reactivity is affected as a result. I will show how the thickness of the oxide skin is greatly dependent on the functional group of the ligands anchored to the surface of the NP and I will explain these results from both a kinetics and a thermodynamics perspective. Finally, surprising results on the effect that the oxide thickness has on the chemical reactivity of ga NPs, during the previously mentioned GRR, will be discussed. Overall, this work reveals the importance of the ligand's choice when studying Ga-based NPs and illustrates a new approach to the synthesis of multimetallic structures based on LMs, providing the basis for its extension to many more systems with increased level of complexity.

Exploring the chemistry of liquid metal Ga nanoparticles

ACS Spring 2022

The official archive and repository for all ACS Meetings & Expositions abstracts and select posters or presentations.