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Thick Two-Dimensional Water Film Confined between the Atomically Thin Mica Nanosheet and Hydrophilic Substrate
Langmuir ( IF 3.7 ) Pub Date : 2019-03-25 00:00:00 , DOI: 10.1021/acs.langmuir.8b04232 Cong Wei 1 , Weihao Zhao 1 , Xiaotong Shi 1 , Chengjie Pei 1 , Pei Wei 1 , Jindong Zhang 1 , Hai Li 1
Langmuir ( IF 3.7 ) Pub Date : 2019-03-25 00:00:00 , DOI: 10.1021/acs.langmuir.8b04232 Cong Wei 1 , Weihao Zhao 1 , Xiaotong Shi 1 , Chengjie Pei 1 , Pei Wei 1 , Jindong Zhang 1 , Hai Li 1
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The interesting properties of water molecules confined in a two-dimensional (2D) environment have aroused great attention. However, the study of 2D-confined water at the hydrophilic–hydrophilic interface is largely unexplored due to the lack of appropriate system. In this work, the behavior of water molecules confined between an atomically thin mica nanosheet and a hydrophilic SiO2/Si substrate was investigated using an atomic force microscope in detail at ambient conditions. The confined water molecules aggregated as droplets when the relative humidity (RH) of the environment was 11%. A large-area 2D water film with a uniform thickness of ∼2 nm was observed when the mica flake was incubated at 33% RH for 1 h before being mechanically exfoliated on a SiO2/Si substrate. Interestingly, the water film showed ordered edges with a predominant angle of 120°, which was the same with the lattice orientation of the mica nanosheet on top of it. The water film showed a fluidic behavior at the early stage and reached a stable state after 48 h under ambient conditions. The surface properties of the upper mica nanosheet and the underlying substrate played a crucial role in manipulating the behavior of confined water molecules. When the surface of the upper mica nanosheet was modified by Na+, Ni2+, and aminopropyltriethoxysilane (APS), only some small water droplets were observed instead of a water film. The surface of the underlying SiO2/Si substrate was functionalized by hydrophilic APS and hydrophobic octadecyltrimethoxysiliane (OTS). The small water droplets were imaged on a hydrophobic OTS-SiO2/Si substrate, while the water film with regular edges was maintained on a hydrophilic APS-SiO2/Si substrate. Our results might provide an alternative molecular view for investigating structures and properties of confined water molecules in 2D environments.
中文翻译：
限制在原子薄云母纳米片和亲水性基质之间的二维水膜厚
局限在二维（2D）环境中的水分子有趣的特性引起了极大的关注。但是，由于缺乏合适的系统，在亲水-亲水界面上的二维受限水的研究尚未得到开发。在这项工作中，使用原子力显微镜在环境条件下详细研究了被限制在原子薄的云母纳米片和亲水性SiO 2 / Si衬底之间的水分子的行为。当环境的相对湿度（RH）为11％时，受限水分子会聚集成液滴。当将云母片在SiO 2上机械剥离之前，将其在33％RH下孵育1小时时，观察到了均匀厚度约为2 nm的大面积二维水膜。/ Si基板。有趣的是，水膜显示出有序的边缘，其主角为120°，与位于其顶部的云母纳米片的晶格取向相同。水膜在早期显示出流体行为，并且在环境条件下48小时后达到稳定状态。上层云母纳米片和下层基底的表面特性在控制受限水分子的行为中起着至关重要的作用。当上云母纳米片的表面用钠改性+，镍2+ ，和氨基丙基三乙氧基（APS），只有一些小水滴，观察到的，而不是一个水膜。底层SiO 2的表面/ Si底物通过亲水性APS和疏水性十八烷基三甲氧基硅烷（OTS）进行功能化。将小水滴成像在疏水性OTS-SiO 2 / Si基板上，而具有规则边缘的水膜则保持在亲水性APS-SiO 2 / Si基板上。我们的结果可能为研究二维环境中受限水分子的结构和性质提供了另一种分子观点。
更新日期：2019-03-25
中文翻译：
限制在原子薄云母纳米片和亲水性基质之间的二维水膜厚
局限在二维（2D）环境中的水分子有趣的特性引起了极大的关注。但是，由于缺乏合适的系统，在亲水-亲水界面上的二维受限水的研究尚未得到开发。在这项工作中，使用原子力显微镜在环境条件下详细研究了被限制在原子薄的云母纳米片和亲水性SiO 2 / Si衬底之间的水分子的行为。当环境的相对湿度（RH）为11％时，受限水分子会聚集成液滴。当将云母片在SiO 2上机械剥离之前，将其在33％RH下孵育1小时时，观察到了均匀厚度约为2 nm的大面积二维水膜。/ Si基板。有趣的是，水膜显示出有序的边缘，其主角为120°，与位于其顶部的云母纳米片的晶格取向相同。水膜在早期显示出流体行为，并且在环境条件下48小时后达到稳定状态。上层云母纳米片和下层基底的表面特性在控制受限水分子的行为中起着至关重要的作用。当上云母纳米片的表面用钠改性+，镍2+ ，和氨基丙基三乙氧基（APS），只有一些小水滴，观察到的，而不是一个水膜。底层SiO 2的表面/ Si底物通过亲水性APS和疏水性十八烷基三甲氧基硅烷（OTS）进行功能化。将小水滴成像在疏水性OTS-SiO 2 / Si基板上，而具有规则边缘的水膜则保持在亲水性APS-SiO 2 / Si基板上。我们的结果可能为研究二维环境中受限水分子的结构和性质提供了另一种分子观点。
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