Ye Shuonan, Chen Xiaobo, Sun Xianhu, Patel Shyam Bharatkumar, Wu Yupeng, Singler Timothy J, Zhang Pu, Zhou Guangwen
Department of Mechanical Engineering & Materials Science and Engineering Program, State University of New York at Binghamton, Binghamton, New York 13902, United States.
ACS Nano. 2024 Sep 10;18(36):25107-25117. doi: 10.1021/acsnano.4c06764. Epub 2024 Aug 27.
Eutectic gallium-indium (EGaIn), a room-temperature liquid metal, has garnered significant attention for its applications in soft electronics, multifunctional materials, energy engineering and drug delivery. A key factor influencing these diverse applications is the spontaneous formation of a native passivating oxide shell that not only encapsulates the liquid metal but also alters the properties from the bulk counterpart. Using environmental scanning transmission electron microscopy, we report observations of the oxidation of EGaIn nanoparticles by ambient air under high-energy electron beam irradiation. Our findings demonstrate that uneven oxide shell growth, driven by inward diffusion of adsorbed O species, creates unbalanced stresses. This compels the liquid metal to deform toward regions with slower oxide growth, resulting in shell rupture and allowing the liquid metal core to flow out. This process initiates top-down self-similar replication of the core-shell liquid metal nanoparticles, causing larger particles to break down into smaller particles. Additionally, internal oxidation triggers phase separation within the liquid core, ultimately leading to the pulverization of the liquid metal into finer solid particles rich in indium. These mechanistic insights into the oxidation behavior of the liquid metal hold practical implications for leveraging this process to reconfigure EGaIn nanoparticles for various applications.
共晶镓铟（EGaIn）是一种室温液态金属，因其在软电子学、多功能材料、能源工程和药物递送等领域的应用而备受关注。影响这些不同应用的一个关键因素是自发形成的天然钝化氧化壳，它不仅包裹着液态金属，还会改变其与块状对应物不同的性质。利用环境扫描透射电子显微镜，我们报告了在高能电子束照射下，EGaIn纳米颗粒被环境空气氧化的观察结果。我们的研究结果表明，由吸附的氧物种向内扩散驱动的不均匀氧化壳生长会产生不平衡应力。这迫使液态金属向氧化生长较慢的区域变形，导致壳破裂，并使液态金属核心流出。这个过程引发了核壳液态金属纳米颗粒的自上而下的自相似复制，使较大的颗粒分解成较小的颗粒。此外，内部氧化会引发液芯内的相分离，最终导致液态金属粉碎成富含铟的更细固体颗粒。这些对液态金属氧化行为的机理见解对于利用这一过程重新配置EGaIn纳米颗粒以用于各种应用具有实际意义。
