Flocculation of MXenes and Their Use as 2D Particle Surfactants for Capsule Formation
Flocculation of MXenes and Their Use as 2D Particle Surfactants for Capsule Formation
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DOI：
10.1021/acs.langmuir.0c03244
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发表时间：
2021-02-16
期刊：
影响因子：
3.9
通讯作者：
Pentzer, Emily B.
中科院分区：
文献类型：
--
作者：
Cao, Huaixuan;Escamilla, Maria;Pentzer, Emily B.
MXenes是过渡金属碳化物或氮化物，近年来因其高导电性、高催化活性、亲水性和多种表面化学性质而受到广泛关注。然而，高亲水性和负zeta电位限制了MXene纳米片的可加工性和界面组装性。先前关于修饰MXenes的分散性和润湿性的例子主要集中在使用有机配体，如烷基胺，或与三乙氧基硅烷进行共价修饰。在这里，我们报告了一种简单的方法，通过使用普通无机盐（如NaCl）絮凝纳米片来获得MXene稳定的水包油乳液，并演示了使用这些皮克林乳液来制备MXene和聚合物外壳的胶囊。以Ti3C2Tz纳米片作为MXene的代表。通过光学显微镜成像确定，盐絮凝的MXene纳米片产生的乳液可以稳定数天。二异氰酸酯在不连续油相中的掺入和二胺在连续水相中的掺入导致了界面聚合和胶囊的形成。采用傅里叶变换红外光谱（FTIR）、x射线光电子能谱（XPS）和扫描电子显微镜（SEM）对胶囊进行了表征，证实了聚合物和纳米片的存在。向胶囊中添加乙醇导致甲苯核心的去除和壳结构的保留。在不使用配体或共表面活性剂的情况下，在流体-流体界面上组装MXene纳米片的能力扩大了与生物医学工程、水净化、储能、电磁电子学、催化等相关的可获得材料结构。
MXenes, transition metal carbides or nitrides, have gained great attention in recent years due to their high electrical conductivity and catalytic activity, hydrophilicity, and diverse surface chemistry. However, high hydrophilicity and negative zeta potential of the MXene nanosheets limit their processability and interfacial assembly. Previous examples for modifying the dispersibility and wettability of MXenes have focused on the use of organic ligands, such as alkyl amines, or covalent modification with triethoxysilanes. Here, we report a simple method to access MXene-stabilized oil-in-water emulsions by using common inorganic salts (e.g., NaCl) to flocculate the nanosheets and demonstrate the use of these Pickering emulsions to prepare capsules with shells of MXene and polymer. Ti3C2Tz nanosheets are used as the representative MXene. The salt-flocculated MXene nanosheets produce emulsions that are stable for days, as determined by optical microscopy imaging. The incorporation of a diisocyanate in the discontinuous oil phase and diamine in the continuous water phase led to interfacial polymerization and the formation of capsules. The capsules were characterized by Fourier transform infrared (FTIR) spectroscopy, X-ray photoelectron spectroscopy (XPS), and scanning electron microscopy (SEM), confirming the presence of both polymer and nanosheets. The addition of ethanol to the capsules led to the removal of the toluene core and retention of the shell structure. The ability to assemble MXene nanosheets at fluid-fluid interfaces without the use of ligands or cosurfactants expands the accessible material constructs relevant for biomedical engineering, water purification, energy storage, electromagnetic electronics, catalysis, and so on.