Modulating the Reactivity of Liquid Ga Nanoparticle Inks by Modifying Their Surface Chemistry

Micro- and nanosized particles of liquid metals, particularly Ga-based alloys, are attracting increasing attention for applications in several fields. The surface functionalization of Ga-based nanoparticles (NPs) with organic ligands renders easily processable inks. However, little is known about the interaction of these molecules with the native oxide skin, which regulates many properties of liquid metal NPs. Here, we investigate the impact of selected capping ligands on the native oxide thickness of Ga NPs and on their chemical reactivity, choosing the galvanic replacement reaction (GRR) as one example. We demonstrate that amines and carboxylic acids promote thicker oxide shells while thiols and phosphines hinder the oxide growth. Upon pondering thermodynamics and kinetics factors, we conclude the affinity of the anchoring group toward the metal core being the major driver in determining the oxide thickness. We go on to prove that thicker shells foster the formation of Cu-Ga nanodimers following the reaction of the Ga NPs with a copper-amine complex. In contrast, thinner oxides lead to formation of isolated Cu NPs. This study reveals the importance of the choice of ligand when studying Ga-based metal NPs for different applications since both their surface chemistry and reactivity are largely affected by this decision.

Automated summary

Micro- and nanosized particles of liquid metals, particularly Ga-based alloys, have gained attention for various applications. Surface functionalization of Ga-based nanoparticles with organic ligands allows for easily processable inks. This study investigates the interaction between these ligands and the native oxide skin of liquid metal nanoparticles, which plays an important role in regulating their properties. The choice of ligand is found to affect the oxide thickness and chemical reactivity of Ga nanoparticles. Thermodynamics and kinetics suggest that it is the affinity of the anchoring group towards the metal core that determines oxide thickness. Thicker oxide shells promote the formation of Cu-Ga nanodimers, while thinner oxides lead to isolated Cu nanoparticles. This research emphasizes the importance of selecting the appropriate ligand when studying Ga-based metal nanoparticles for different applications.