Using H2O2 as a green oxidant to produce fluorescent GaOOH nanomaterials from a liquid metal

Sustainable sonoprocess for synthesizing γ-Ga2O3/In3Sn core-shell submicron particles via acoustic emulsification and oxidation of molten EGaInSn at room temperature

This study investigated the sustainable room-temperature synthesis of In3Sn/γ-Ga2O3 core-shell particles via an acoustic route using molten eutectic Ga-In-Sn alloy (EGaInSn). Sonication was used for the emulsification and oxidation steps. During the emulsification step, the sonication of molten EGaInSn in ethanol (EtOH) at 45 kHz facilitated the formation of the smallest EGaInSn particles (average diameter, Dav = 782 nm). In terms of EGaInSn particle size, 45 kHz sonication was suitable for emulsification of molten EGaInSn and ethanol system than 24 kHz sonication. During the oxidation step, the preferential oxidation of Ga in the EGaInSn particles occurred via sonication in a solution of EtOH and hydrazine monohydrate (N2H4·H2O). This selective oxidation of Ga on the surface of the EGaInSn particles resulted in the formation of In3Sn/γ-Ga2O3 core-shell particles via sonication at 45 kHz and room temperature. The entire process eliminated the need for dispersants and high-temperature treatments. Additionally, the process did not generate waste fluid containing counter anions, such as chloride anions. This sustainable sonochemical method offers a carbon-neutral approach for synthesizing functional nanocomposites with improved safety, simplicity, and energy efficiency.

Room-Temperature Liquid Metals for Flexible Electronic Devices

Room-temperature gallium-based liquid metals (RT-GaLMs) have garnered significant interest recently owing to their extraordinary combination of fluidity, conductivity, stretchability, self-healing performance, and biocompatibility. They are ideal materials for the manufacture of flexible electronics. By changing the composition and oxidation of RT-GaLMs, physicochemical characteristics of the liquid metal can be adjusted, especially the regulation of rheological, wetting, and adhesion properties. This review highlights the advancements in the liquid metals used in flexible electronics. Meanwhile related characteristics of RT-GaLMs and underlying principles governing their processing and applications for flexible electronics are elucidated. Finally, the diverse applications of RT-GaLMs in self-healing circuits, flexible sensors, energy harvesting devices, and epidermal electronics, are explored. Additionally, the challenges hindering the progress of RT-GaLMs are discussed, while proposing future research directions and potential applications in this emerging field. By presenting a concise and critical analysis, this paper contributes to the advancement of RT-GaLMs as an advanced material applicable for the new generation of flexible electronics.

GaOOH Crystallite Growth on Liquid Metal Microdroplets in Water: Influence of the Local Environment

Gallium-based liquid metals form alloys with a melting point close to or below room temperature. On the surface of these liquid metals, a thin oxide skin is formed once in contact with oxygen, and this oxide skin can be leveraged to stabilize liquid metal micro- and nanodroplets in a liquid. During sonication and storage of these droplets in aqueous solution, gallium oxide hydroxide (GaOOH) forms on these droplets, and given enough time or treatment with heat, a full shape transition and dealloying are observed. In this article, we show that GaOOH can be grown at room temperature and that the growth is dependent on both the local environment and temperature. GaOOH growth on liquid metal microdroplets located at the air/water interface is considerably faster than in the bulk phase. Interestingly, hydrolysis to GaOOH is hampered and stops at 15 °C in bulk water after 6 h. In contrast, hydrolysis commences even at 15 °C for liquid metal microdroplets located at the air/water interface, and full surface coverage is obtained after around 24 h (compared to 12 h at 25 °C at the air/water interface). The X-ray photoelectron spectroscopy (XPS) measurement suggests that gallium oxide is dissolved and Ga(OH)₃ is formed as a precursor that reacts in a downstream reaction toward GaOOH. This improved understanding of the GaOOH formation can be leveraged to control the liquid metal micro- and nanodroplet shape and composition (i.e., for biomedical applications).