Simulation-based molecular force on the surface of gallium-based liquid metals

Abstract

Owing to their excellent properties, gallium-based liquid metal materials have been continuously discovered and innovated for various applications, but the self-confined oxide products formed on their surfaces have always been the key to elucidating their nature. In order to study the nature of the reaction and reveal its mechanism, we utilized sophisticated molecular dynamics simulations to meticulously examine their behaviors in an aqueous setting, focusing on four gallium oxide derivatives—two types of gallium oxide (Ga₂O₃, GA1, trigonal-shaped; Ga₂O₃, GA2, linear-shaped), gallium oxide hydroxide (GaOOH, GA3), and gallium hydroxide (Ga(OH)₃, GA4). Based on previous studies, as a proof of concept, the intricate dynamics of gallium derivatives and their interactions with azo dye (Ponceau S) under variable solution conditions are pivotal for developing advanced material applications. A key aspect of our study is that we explored the temperature sensitivity of these interactions, revealing that although van der Waals and electrostatic forces between the gallium species and Ponceau S decrease with increasing temperature, the dye continues to aggregate at the heart of these clusters. Of particular note are the distinct preferences in the binding hierarchy among the gallium derivatives to Ponceau S, with GA2 emerging as the most dominant due to its strong polar interactions, closely followed by GA4, which engages through hydrogen bonding. Conversely, GA1 and GA3 display limited involvement in clustering, suggesting a lack of strong affinity for the dye. Additionally, we discovered the critical role of ions in mediating these interactions, especially the unexpected attraction of GA4 and GA1 towards sodium ions (Na⁺), challenging traditional assumptions and potentially reconfiguring gallium species distribution and aggregate stability. Chloride ions (Cl⁻) showed no such selectivity, reinforcing the need for careful consideration of ionic environments to understand the clustering phenomena. In conclusion, our findings emphasize the temperature-dependent and ion-influenced nature of gallium derivative interactions with Ponceau S, underscoring the importance of environmental factors in the design and performance prediction of gallium-based materials. This study is of great significance for revealing the force of interface reactions on liquid metal surfaces, setting the stage for future inquiries into other physicochemical aspects and opening avenues for exploiting controlled aggregation pathways in liquid environments for innovative material synthesis.