Polydopamine Shell as a Ga³⁺ Reservoir for Triggering Gallium–Indium Phase Separation in Eutectic Gallium–Indium Nanoalloys

Abstract

Low melting point eutectic systems, such as the eutectic gallium–indium (EGaIn) alloy, offer great potential in the domain of nanometallurgy; however, many of their interfacial behaviors remain to be explored. Here, a compositional change of EGaIn nanoalloys triggered by polydopamine (PDA) coating is demonstrated. Incorporating PDA on the surface of EGaIn nanoalloys renders core–shell nanostructures that accompany Ga–In phase separation within the nanoalloys. The PDA shell keeps depleting the Ga3+ from the EGaIn nanoalloys when the synthesis proceeds, leading to a Ga3+-coordinated PDA coating and a smaller nanoalloy. During this process, the eutectic nanoalloys turn into non-eutectic systems that ultimately result in the solidification of In when Ga is fully depleted. The reaction of Ga3+-coordinated PDA-coated nanoalloys with nitrogen dioxide gas is presented as an example for demonstrating the functionality of such hybrid composites. The concept of phase-separating systems, with polymeric reservoirs, may lead to tailored materials and can be explored on a variety of post-transition metals.

Emerging Role of Liquid Metals in Sensing

“…In another study on the effect of functional coating on the performance of LM-based gas sensors, the surfaces of EGaIn NPs were coated with polydopamine (PDA) shells at various thicknesses. 160 According to the obtained results, surface coating of NPs accompanied by Ga 3+ diffusion and coordination into PDA shells resulted in an enhancement in interfacial polarity and induced Ga−In phase separation. While the increase in the interfacial polarity favored NO 2 sensing performance, Ga−In phase separation showed a counteracting effect by increasing the electrical resistivity (due to lower conductivity of In compared to EGaIn).…”

“…Semiconductor metal oxides (SMOs) are the most popular materials for gas sensing applications where changes in electrical properties of SMO are tracked upon physical or chemical interactions with target gaseous compounds. , When it comes to Ga-based LMs, the native oxide layer, rapidly formed on the surface, is known to feature semiconducting properties suited for gas sensing applications. , The most interesting feature of LM-based gas sensing interfaces is tailorable sensing properties achieved via manipulation of morphology and size of sensing elements as well as versatile deposition of functional coatings on LMs droplets. , …”

“…(B) PDA-coated EGaIn particles utilized for NO 2 sensing: (i) disposition of different PDA thicknesses and (ii) their impact on gas sensing performance. Reproduced from ref . Copyright 2021 American Chemical Society.…”

“…157,158 The most interesting feature of LM-based gas sensing interfaces is tailorable sensing properties achieved via manipulation of morphology and size of sensing elements 159 as well as versatile deposition of functional coatings on LMs droplets. 160,161 Conventional LM-Based Gas Sensors. Traditionally, thin films of gallium oxides have been exploited as gas sensing elements for both reducing and oxidizing gaseous species.…”

Assembly of surface-independent polyphenol/liquid gallium composite nanocoatings

“…25,27 However, the LM surfaces possess limited interactions with external substrates. [31][32][33][34] This hinders the practical utilization of Ga NPs as an antibacterial depot since it requires the processing of the Ga NPs as stable surface coatings. Such a surface coating process of Ga NPs has remained a critical bottleneck for their extensive use in antibacterial applications.…”